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2010

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Articles 4381 - 4410 of 5375

Full-Text Articles in Engineering

Experimental Studies Of Liquefaction And Densification Of Liquid Oxygen, Jonathan Koert Partridge Jan 2010

Experimental Studies Of Liquefaction And Densification Of Liquid Oxygen, Jonathan Koert Partridge

Electronic Theses and Dissertations

Rocketry employs cryogenic refrigeration to increase the density of propellants, such as oxygen, and stores the propellant as a liquid. In addition to propellant liquefaction, cryogenic refrigeration can also conserve propellant and provide propellant subcooling and densification. Previous studies analyzed vapor conditioning of a cryogenic propellant, which occurred by either a heat exchanger positioned in the vapor or by using the vapor as the working fluid in a refrigeration cycle. This study analyzes the refrigeration effects of a heat exchanger located beneath the vapor-liquid interface of liquid oxygen. This study predicts the mass liquefaction rate and heat transfer coefficient for …

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Evaluating The Benefits Of 3d Stereo In Modern Video Games, Tad Litwiller Jan 2010

Evaluating The Benefits Of 3d Stereo In Modern Video Games, Tad Litwiller

Electronic Theses and Dissertations

We present a study that investigates user performance benefits of 3D stereo in modern video games. Based on an analysis of several video games that are best suited for use with commercial 3D stereo drivers and vision systems, we chose five modern titles focusing on racing, first person shooter, third person shooter, and sports game genres. For each game, quantitative and qualitative measures were taken to determine if users performed better and learned faster in the experimental group (3D stereo display) than in the control group (2D display). A game experience pre-questionnaire was used to classify participants into beginner, intermediate, …

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The Simulation And Control Of A Grid-Connected Wind Energy Conversion System, Shauna Mccartney Jan 2010

The Simulation And Control Of A Grid-Connected Wind Energy Conversion System, Shauna Mccartney

Electronic Theses and Dissertations

With the rising cost of petroleum, concerns about exhausting the fossil fuels we depend on for energy, and the subsequent impacts that the burning of these types of fuels have on the environment, countries around the world are paying close attention to the development of renewable types of energy. Consequently, researchers have been trying to develop ways to take advantage of different types of clean and renewable energy sources. Wind energy production, in particular, has been growing at an increasingly rapid rate, and will continue to do so in the future. In fact, it has become an integral part in …

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Conjugate Heat Transfer On A Gas Turbine Blade, Santiago Salazar Jan 2010

Conjugate Heat Transfer On A Gas Turbine Blade, Santiago Salazar

Electronic Theses and Dissertations

Clearances between gas turbine casings and rotating blades is of quite importance on turbo machines since a significant loss of efficiency can occur if the clearances are not predicted accordingly. The radial thermal growths of the blade may be over or under predicted if poor assumptions are made on calculating the metal temperatures of the surfaces exposed to the fluid. The external surface of the blade is exposed to hot gas temperatures and it is internally cooled with air coming from the compressor. This cold air enters the radial channels at the root of the blade and then exists at …

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Accelerated Life Testing Of Subsea Equipment Under Hydrostatic Pressure, Amar Raja Thiraviam Jan 2010

Accelerated Life Testing Of Subsea Equipment Under Hydrostatic Pressure, Amar Raja Thiraviam

Electronic Theses and Dissertations

Accelerated Life Testing (ALT) is an effective method of demonstrating and improving product reliability in applications where the products are expected to perform for a long period of time. ALT accelerates a given failure mode by testing at amplified stress level(s) in excess of operational limits. Statistical analysis (parameter estimation) is then performed on the data, based on an acceleration model to make life predictions at use level. The acceleration model thus forms the basis of accelerated life testing methodology. Well established accelerated models such as the Arrhenius model and the Inverse Power Law (IPL) model exist for key stresses …

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Study Of The Interactions Of Proteins, Cells And Tissue With Biomaterials, Abhijeet Bhalkikar Jan 2010

Study Of The Interactions Of Proteins, Cells And Tissue With Biomaterials, Abhijeet Bhalkikar

Electronic Theses and Dissertations

Bioengineering is the application of engineering principles to address challenges in the fields of biology and medicine. Biomaterials play a major role in bioengineering. This work employs a three level approach to study the various interactions of biomaterials with proteins, cells and tissue in vitro. In the first study, we qualitatively and quantitatively analyzed the process of protein adsorption of two enzymes to two different surface chemistries, which are commonly used in the field. In the second study, we attempted to engineer a tissue construct to build a biocompatible interface between a titanium substrate and human skin. In the third …

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Analysis And Optimization Of A Solar Thermal Collector With Integrated Storage, Monica Bonadies Jan 2010

Analysis And Optimization Of A Solar Thermal Collector With Integrated Storage, Monica Bonadies

Electronic Theses and Dissertations

Solar energy, a topic popular in the United States during the oil embargo of the 1970’s, has become a relevant topic once more with the current focus on reducing greenhouse emissions. Solar thermal energy in particular has become popular as it uses existing steam turbine technology to produce electricity, with the benefit of using solar energy to produce steam rather than coal or nuclear heat sources. Solar thermal can also be used at lower temperatures to heat water for pools or for residential use. While this energy source has its benefits, it has the problem of being opportunistic – the …

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Mechanical Properties Of Carbon Nanotube/Metal Composites, Ying Sun Jan 2010

Mechanical Properties Of Carbon Nanotube/Metal Composites, Ying Sun

Electronic Theses and Dissertations

Carbon nanotubes (CNTs) have captured a great deal of attention worldwide since their discovery in 1991. CNTs are considered to be the stiffest and strongest material due to their perfect atomic arrangement and intrinsic strong in-plane sp 2—sp 2 covalent bonds between carbon atoms. In addition to mechanical properties, CNTs have also shown exceptional chemical, electrical and thermal properties. All these aspects make CNTs promising candidates in the development of novel multi-functional nanocomposites. Utilizing CNTs as fillers to develop advanced nanocomposites still remains a challenge, due to the lack of fundamental understanding of both material processing at the nanometer scale …

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Structural Health Monitoring Of A Stadium For Evaluating Human Comfort And Structural Performance, Hasan Sazak Jan 2010

Structural Health Monitoring Of A Stadium For Evaluating Human Comfort And Structural Performance, Hasan Sazak

Electronic Theses and Dissertations

Light and rapid constructions as well as considerations such as improved line of sight and increased capacity for modern stadium structures make them vulnerable for vibration serviceability problems. These problems are also observed at convention centers, large shopping malls, concert halls and ballrooms. Especially when the individuals in a crowd are involved in some sort of coordinated motion, this type of loading creates the most potential for high levels of vibration. In order to understand the causes of vibration, vibration levels, service and safety levels, Structural Health Monitoring (SHM) can be implemented to track and evaluate performance of a structure …

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Stress Concentration Factors For V-Notched Plates Under Axisymmetric Pressure, Nathan J. Mutter Jan 2010

Stress Concentration Factors For V-Notched Plates Under Axisymmetric Pressure, Nathan J. Mutter

HIM 1990-2015

The topic of this thesis is the investigation of the local states of stress resulting from the introduction of av-notch in a coaxial circle on the pressurized surface of a circumferentially clamped plate subject to axisymmetric loading. The understanding of the fracture behavior of a component experiencing such a condition is of particular interest to the aerospace and defense industries where circular plate components are often utilized. In such applications, it is imperative that the designer be able to predict the loading conditions facilitating dynamic fracture. As a step towards solving such problems, the quasi-static analogy is studied. Specifically, the …

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Multi-Pole Permanent Magnet Motor Design And Control For High Performance Electromechanical Actuation In All Electric Aircraft, Jared C. Bindl Jan 2010

Multi-Pole Permanent Magnet Motor Design And Control For High Performance Electromechanical Actuation In All Electric Aircraft, Jared C. Bindl

HIM 1990-2015

The evolution of aircraft has led into a large increase in the demand for electrically integrated subsystems. Part of this demand is the transformation of a centralized hydraulic systems to independently operated electrical subsystems. The result of this overhaul will decrease aircraft weight, increase reliability, reduce aircraft lifetime maintenance and cost, and help to increase the control of power distribution. This thesis proposes the design methodology of a multi-pole permanent magnet (PM) motor with a capability to operate at high temperature. High temperature capability is one of the key requirements to implement electromechanical actuation for aircraft flight control, replace hydraulic …

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Three-Port Micro-Inverter With Power Decoupling Capability For Photovoltaic (Pv) Systems Applications, Souhib Harb Jan 2010

Three-Port Micro-Inverter With Power Decoupling Capability For Photovoltaic (Pv) Systems Applications, Souhib Harb

Electronic Theses and Dissertations

The Photovoltaic (PV) systems have been realized using different architectures, starting with the string and centralized PV system to the modular PV system. Presently, decentralized inverters are being developed at the PV panel power level (known as AC – PV Modules). Such new PV systems are becoming more attractive and many expect this will be the trend of the future. The AC-Module PV system consists of an inverter attached to one PV panel. This integration requires that both devices have the same life-span. Although, the available commercial inverters have a relatively short life-span (10 years) compared to the 25 –year …

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Toward A Real-Time Celestial Body Information System, Brian Mitchell Guise Jan 2010

Toward A Real-Time Celestial Body Information System, Brian Mitchell Guise

Electronic Theses and Dissertations

The National Aeronautics and Space Administration maintains a challenging schedule of planned and on-going space exploration missions that extend to the outer reaches of our galaxy. New missions represent a huge investment, in terms of actual costs for equipment and support infrastructure, and personnel training. The success of a mission is critical considering both the monetary investment, and for manned missions, the lives which are put at risk. Tragedies involving Challenger, Columbia, Apollo 7, and the near tragedy of Apollo 13 exemplify that space exploration is a dangerous endeavor, posing extreme environmental conditions on both equipment and personnel. NASA, the …

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Combustion Dynamics And Fluid Mechanics In Acoustically Perturbed Non-Premixed Swirl-Stabilized Flames., Uyi Idahosa Jan 2010

Combustion Dynamics And Fluid Mechanics In Acoustically Perturbed Non-Premixed Swirl-Stabilized Flames., Uyi Idahosa

Electronic Theses and Dissertations

The prevalence of gas turbines operating in primarily lean premixed modes is predicated on the need for lower emissions and increased efficiency. An enhancement in the mixing process through the introduction of swirl in the combustion reactants is also necessary for flame stabilization. The resulting lean swirling flames are often characterized by a susceptibility to feedback between velocity, pressure and heat release perturbations with a potential for unstable self-amplifying dynamics. The existing literature on combustion dynamics is predominantly dedicated to premixed flame configurations motivated by power generation and propulsive gas turbine applications. In the present research effort, an investigation into …

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Enterprise Business Alignment Using Quality Function Deployment, Multivariate Data Analysis And Business Modeling Tools, Diala Gammoh Jan 2010

Enterprise Business Alignment Using Quality Function Deployment, Multivariate Data Analysis And Business Modeling Tools, Diala Gammoh

Electronic Theses and Dissertations

This dissertation proposes two novel ideas to enhance the business strategy alignment to customer needs. The proposed business alignment clock is a new illustration to the relationships between customer requirements, business strategies, capabilities and processes. To line up the clock and reach the needed alignment for the enterprise, a proposed clock mechanism is introduced. The mechanism integrates the Enterprise Business Architecture (EBA) with the House of Quality (HoQ). The relationship matrix inside the body of the house is defined using multivariate data analysis techniques to accurately measure the strength of the relationships rather than defining them subjectively. A statistical tool, …

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Highly Integrated Dc-Dc Converters, Hongwei Jia Jan 2010

Highly Integrated Dc-Dc Converters, Hongwei Jia

Electronic Theses and Dissertations

A monolithically integrated smart rectifier has been presented first in this work. The smart rectifier, which integrates a power MOSFET, gate driver and control circuitry, operates in a self-synchronized fashion based on its drain-source voltage, and does not need external control input. The analysis, simulation, and design considerations are described in detail. A 5V, 5-µm CMOS process was used to fabricate the prototype. Experimental results show that the proposed rectifier functions as expected in the design. Since no dead-time control needs to be used to switch the sync-FET and ctrl-FET, it is expected that the body diode losses can be …

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Development Of An Improved Microwave Ocean Surface Emissivity Radiative Transfer Model, Salem El-Nimri Jan 2010

Development Of An Improved Microwave Ocean Surface Emissivity Radiative Transfer Model, Salem El-Nimri

Electronic Theses and Dissertations

An electromagnetic model is developed for predicting the microwave blackbody emission from the ocean surface over a wide range of frequencies, incidence angles, and wind vector (speed and direction) for both horizontal and vertical polarizations. This ocean surface emissivity model is intended to be incorporated into an oceanic radiative transfer model to be used for microwave radiometric applications including geophysical retrievals over oceans. The model development is based on a collection of published ocean emissivity measurements obtained from satellites, aircraft, field experiments, and laboratory measurements. This dissertation presents the details of methods used in the ocean surface emissivity model development …

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Structural Characterization Of Sputter-Deposited Ss304+Xal (X = 0, 4, 7 And 10 Wt.%) Coatings And Mechanically Milled Ti, Zr And, Uma Maheswara Seelam Jan 2010

Structural Characterization Of Sputter-Deposited Ss304+Xal (X = 0, 4, 7 And 10 Wt.%) Coatings And Mechanically Milled Ti, Zr And, Uma Maheswara Seelam

Electronic Theses and Dissertations

Study of the metastable phases obtained by non-equilibrium processing techniques has come a long way during the past five decades. New metastable phases have often given new perspectives to the research on synthesis of novel materials systems. Metastable materials produced by two non-equilibrium processing methods were studied for this dissertation- 304-type austenitic stainless steel (SS304 or Fe-18Cr-8Ni)+aluminum coatings produced by plasma enhanced magnetron sputter-deposition (PEMS) and nanocrystalline Ti, Zr and Hf powders processed by mechanical milling (MM). The objective of the study was to understand the crystallographic and microstructural aspects of these materials. Four SS304+Al coatings with a nominal Al …

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Mitigating Misbehavior In Wireless Networks: A Game Theoretic Approach, Wenjing Wang Jan 2010

Mitigating Misbehavior In Wireless Networks: A Game Theoretic Approach, Wenjing Wang

Electronic Theses and Dissertations

In a distributed wireless system, multiple network nodes behave cooperatively towards a common goal. Though such assumptions on cooperation are desirable (e.g., controlling the transmit power level, reducing interference for each other, revealing private information, adhering to network policies) for analyzing and modeling, certain nodes belonging to a real-world system have often shown to deviate. These nodes, known as misbehaving nodes, bring more challenges to the design of the wireless network because the unreliable channel makes the actions of the nodes hidden from each other. In this dissertation, we analyze two types of misbehavior, namely, selfish noncooperation and malicious attacking. …

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Improving Performance And Programmer Productivity For I/O-Intensive High Performance Computing Applications, Saba Sehrish Jan 2010

Improving Performance And Programmer Productivity For I/O-Intensive High Performance Computing Applications, Saba Sehrish

Electronic Theses and Dissertations

Due to the explosive growth in the size of scientific data sets, data-intensive computing is an emerging trend in computational science. HPC applications are generating and processing large amount of data ranging from terabytes (TB) to petabytes (PB). This new trend of growth in data for HPC applications has imposed challenges as to what is an appropriate parallel programming framework to efficiently process large data sets. In this work, we study the applicability of two programming models (MPI/MPI-IO and MapReduce) to a variety of I/O-intensive HPC applications ranging from simulations to analytics. We identify several performance and programmer productivity related …

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An Optimal Control Approach For Determiniation Of The Heat Loss Coefficient In An Ics Solar Domestic Water Heating System, Camilo Gil Jan 2010

An Optimal Control Approach For Determiniation Of The Heat Loss Coefficient In An Ics Solar Domestic Water Heating System, Camilo Gil

Electronic Theses and Dissertations

Water heating in a typical home in the U.S. accounts for a significant portion (between 14% and 25%) of the total home's annual energy consumption. The objective of considerably reducing the home's energy consumption from the utilities calls for the use of onsite renewable energy systems. Integral Collector Storage (ICS) solar domestic water heating systems are an alternative to help meet the hot water energy demands in a household. In order to evaluate the potential benefits and contributions from the ICS system, it is important that the parameter values included in the model used to estimate the system's performance are …

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Comparison Of Traditional Standard Drainfield With Innovative B&G Treatment Bed For Nutrient Removal From Septic Tank Wastewater, Fahim Hossain Jan 2010

Comparison Of Traditional Standard Drainfield With Innovative B&G Treatment Bed For Nutrient Removal From Septic Tank Wastewater, Fahim Hossain

Electronic Theses and Dissertations

Nowadays people are more alert about conservation of water and water scarcity. The amount of usable water is decreasing due to unavailability of pure water for day to day use. Both surface and groundwater is contaminated by untreated wastewater discharged from improper onsite wastewater treatment system, nutrient laden agricultural runoff and increasing use of fertilizer in fields. This elevated nutrient level is increasing the maintenance and operation cost of water treatment plant. So it is an important task to remove those nutrients from wastewater and other water bodies by applying environmental friendly process. In the USA, about 25% homes are …

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Control Of Hydrogen Sulfide Emissionsusing Autotrophic Denitrificationlandfill Biocovers, Daoroong Sungthong Jan 2010

Control Of Hydrogen Sulfide Emissionsusing Autotrophic Denitrificationlandfill Biocovers, Daoroong Sungthong

Electronic Theses and Dissertations

Hydrogen sulfide (H2S), a major odorous component emitted from construction and demolition debris landfills, has received increasing attention. Besides its unpleasant odor, long-term exposure to a very low concentration of H2S can cause a public health issue. Although cover materials such as soil and compost are recommended to be used routinely to control an odor problem from the landfills, the problem still remains. Autotrophic denitrification may have environmental applications including treatment of water, groundwater, wastewater or gaseous streams contaminated with sulfur and/or nitrogen compounds. However, there have been no studies reported in the literature on H2S removal using autotrophic denitrification …

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Architectural Support For Improving Computer Security, Jingfei Kong Jan 2010

Architectural Support For Improving Computer Security, Jingfei Kong

Electronic Theses and Dissertations

Computer security and privacy are becoming extremely important nowadays. The task of protecting computer systems from malicious attacks and potential subsequent catastrophic losses is, however, challenged by the ever increasing complexity and size of modern hardware and software design. We propose several methods to improve computer security and privacy from architectural point of view. They provide strong protection as well as performance efficiency. In our first approach, we propose a new dynamic information flow method to protect systems from popular software attacks such as buffer overflow and format string attacks. In our second approach, we propose to deploy encryption schemes …

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Real-Time Cinematic Design Of Visual Aspects In Computer-Generated Images, Juraj Obert Jan 2010

Real-Time Cinematic Design Of Visual Aspects In Computer-Generated Images, Juraj Obert

Electronic Theses and Dissertations

Creation of visually-pleasing images has always been one of the main goals of computer graphics. Two important components are necessary to achieve this goal --- artists who design visual aspects of an image (such as materials or lighting) and sophisticated algorithms that render the image. Traditionally, rendering has been of greater interest to researchers, while the design part has always been deemed as secondary. This has led to many inefficiencies, as artists, in order to create a stunning image, are often forced to resort to the traditional, creativity-baring, pipelines consisting of repeated rendering and parameter tweaking. Our work shifts the …

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Experimental Analysis On The Effects Of Superficial Liquid And Gas Velocities In The Removal Of Hydrogen Sulfide From A Brine/Oil Mixture, Joshua Lee Jan 2010

Experimental Analysis On The Effects Of Superficial Liquid And Gas Velocities In The Removal Of Hydrogen Sulfide From A Brine/Oil Mixture, Joshua Lee

Electronic Theses and Dissertations

Hydrogen Sulfide (H2S) is a harmful gas produced during petroleum extraction that leads to corrosion of drilling tools and pipelines. However, a H2S-scavenging liquid compound, when added to pipelines, interacts with liquids that absorbed H2S to create a non-corrosive bi-product. The interaction is associated with the mixing of gases and liquids. This thesis is a study on the effect of superficial gas and liquid velocities on the scavenger's efficiency. This study employs two experimental setups designed to simulate the mixing of gases and liquids within pipelines. A high pressure closed loop was designed and fabricated to determine the influence of …

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Numerical Modeling Of The Shock Tube Flow Fields Before Andduring Ignition Delay Time Experiments At Practical Conditions, Mouna Lamnaouer Jan 2010

Numerical Modeling Of The Shock Tube Flow Fields Before Andduring Ignition Delay Time Experiments At Practical Conditions, Mouna Lamnaouer

Electronic Theses and Dissertations

An axi-symmetric shock-tube model has been developed to simulate the shock-wave propagation and reflection in both non-reactive and reactive flows. Simulations were performed for the full shock-tube geometry of the high-pressure shock tube facility at Texas A&M University. Computations were carried out in the CFD solver FLUENT based on the finite volume approach and the AUSM+ flux differencing scheme. Adaptive mesh refinement (AMR) algorithm was applied to the time-dependent flow fields to accurately capture and resolve the shock and contact discontinuities as well as the very fine scales associated with the viscous and reactive effects. A conjugate heat transfer model …

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Reconfigurable Computing For Video Coding, Jian Huang Jan 2010

Reconfigurable Computing For Video Coding, Jian Huang

Electronic Theses and Dissertations

Video coding is widely used in our daily life. Due to its high computational complexity, hardware implementation is usually preferred. In this research, we investigate both ASIC hardware design approach and reconfigurable hardware design approach for video coding applications. First, we present a unified architecture that can perform Discrete Cosine Transform (DCT), Inverse Discrete Cosine Transform (IDCT), DCT domain motion estimation and compensation (DCT-ME/MC). Our proposed architecture is a Wavefront Array-based Processor with a highly modular structure consisting of 8*8 Processing Elements (PEs). By utilizing statistical properties and arithmetic operations, it can be used as a high performance hardware accelerator …

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Digital Pulse Width Modulator Techniques For Dc - Dc Converters, Majd Batarseh Jan 2010

Digital Pulse Width Modulator Techniques For Dc - Dc Converters, Majd Batarseh

Electronic Theses and Dissertations

Recent research activities focused on improving the steady-state as well as the dynamic behavior of DC-DC converters for proper system performance, by proposing different design methods and control approaches with growing tendency to using digital implementation over analog practices. Because of the rapid advancement in semiconductors and microprocessor industry, digital control grew in popularity among PWM converters and is taking over analog techniques due to availability of fast speed microprocessors, flexibility and immunity to noise and environmental variations. Furthermore, increased interest in Field Programmable Gate Arrays (FPGA) makes it a convenient design platform for digitally controlled converters. The objective of …

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Assessment Of Aquifer Storage And Recovery Impact On Phosphorus Stability In Lake Sediment, Sha Liu Jan 2010

Assessment Of Aquifer Storage And Recovery Impact On Phosphorus Stability In Lake Sediment, Sha Liu

Electronic Theses and Dissertations

Lake Okeechobee, the second largest natural freshwater lake in the United States, had experienced a historical drought in 2007-2008 and the inflow to Lake Okeechobee has been reduced by 40% of the average daily mean between warm phase and cold phase due to the impact of Atlantic Multidecadal Oscillation in the past six decades. To cope with this water resources management problem, the US Army Corps of Engineers (USACE) proposed the largest national implementation plan of aquifer storage and recovery (ASR) project in the Kissimmee River Basin. Routine operation of ASR will deliver recovered water from ASR wells into the …

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