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Articles 2551 - 2580 of 4566

Full-Text Articles in Engineering

The Calibration, Validation, And Comparison Of Vissim Simulations Using The Two-Fluid Model, Jeremy Crowe Jan 2009

The Calibration, Validation, And Comparison Of Vissim Simulations Using The Two-Fluid Model, Jeremy Crowe

Electronic Theses and Dissertations

The microscopic traffic simulation program VISSIM is a powerful tool that has been used by transportation engineers and urban planners around the world. A VISSIM simulation is meant to depict the performance of the physical road network through the use of modeling tools and behavioral parameters. The process which gets the model to the point of matching real world conditions is called calibration and requires a means of relating the real world to the simulated world. The topic of this thesis discusses a new means of calibration using the two-fluid model. The two-fluid model is a macroscopic modeling technique which …

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Work Zone Effects On Performance Of A Toll Plaza, Jingyu Liu Jan 2009

Work Zone Effects On Performance Of A Toll Plaza, Jingyu Liu

Electronic Theses and Dissertations

No-lane closure workzone is typical during the construction of open road tolling lanes of a toll plaza. The influence of no-lane closure on toll plazas' performance is unknown because very few studies have been conducted to address this topic. The open road tolling (ORT) has become the new trend of operating an efficient toll plaza. So, the upgrading of a toll plaza from gated E-pass to open road E-pass has become common. The better the toll plaza authority knows about the influence of this construction and congestion effects, the better it can serve the costumers. This project mainly deals with …

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A Gis Safety Study And A County-Level Spatial Analysis Of Crashes In The State Of Florida, Ali Darwiche Jan 2009

A Gis Safety Study And A County-Level Spatial Analysis Of Crashes In The State Of Florida, Ali Darwiche

Electronic Theses and Dissertations

The research conducted in this thesis consists of a Geographic Information Systems (GIS) based safety study and a spatial analysis of vehicle crashes in the State of Florida. The GIS safety study is comprised of a County and Roadway Level GIS analysis of multilane corridors. The spatial analysis investigated the use of county-level vehicle crash models, taking spatial effects into account. The GIS safety study examines the locations of high trends of severe crashes (includes incapacitating and fatal crashes) on multilane corridors in the State of Florida at two levels, county level and roadway level. The GIS tool, which is …

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Flow Visualization In Microfluidic Expansion And Mixing, Ehsan Yakhshi-Tafti Jan 2009

Flow Visualization In Microfluidic Expansion And Mixing, Ehsan Yakhshi-Tafti

Electronic Theses and Dissertations

Micro particle image velocimetry (microPIV) is a non-intrusive tool for visualizing flow in micron-scale conduits. Using this investigative instrument, two experimental studies were performed to understand flow behaviors in microfluidic channels - a sudden expansion step flow and laminar velocity profile variation in diffusion driven mixing. First, flow in a backward facing step feature (1:5 expansion ratio) in a microchannel was taken as the subject of microPIV flow visualization. The onset and development of a recirculation flow was studied as a function of flow rate. This flow pattern was further used to investigate two major parameters affecting microPIV measurements; the …

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Study Of The Hydrodynamics Of Droplet Impingement On A Dry Surface Using Lattice Boltzmann Method, Xin Gu Jan 2009

Study Of The Hydrodynamics Of Droplet Impingement On A Dry Surface Using Lattice Boltzmann Method, Xin Gu

Electronic Theses and Dissertations

In this work, a two-phase lattice Boltzmann method (LBM) approach is implemented to investigate the hydrodynamic behavior of a single droplet impingement on a dry surface. LBM is a recently developed powerful technique to compute a wide range of fluid flow problems, especially in applications involving interfacial dynamics and complex geometries. Instead of solving the non-linear Navier-Stokes equations, which are complicated partial differential equations, LBM solves a set of discretized linear equations, which are easy to implement and parallelize. The fundamental idea of LBM is to recover the macroscopic properties of the fluid which obeys Navier-Stokes equations, by using simplified …

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Characterization Of A Hydrogen-Based Synthetic Fuel In A Shock Tube, Troy Flaherty Jan 2009

Characterization Of A Hydrogen-Based Synthetic Fuel In A Shock Tube, Troy Flaherty

Electronic Theses and Dissertations

Shock-tube experiments were performed with syngas mixtures near atmospheric pressure with varying equivalence ratios behind reflected shock waves. Pressure and hydroxyl radical (OH*) emission traces were recorded and used to calculate ignition delay time for a single mixture at equivalence ratios of [phi ]=0.4, 0.7, 1.0, and 2.0 over a range of temperatures from 913-1803 K. The syngas mixture was tested at full concentration as well as with 98% dilution in Argon. The full concentration mixtures were used to compare ignition delay time measurements with the theoretical calculations obtained through the use of chemical kinetics modeling using the Davis et …

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Efficiency Improvement Techniques For High Voltage Capacitor Charging Methods, Michael Islas Jan 2009

Efficiency Improvement Techniques For High Voltage Capacitor Charging Methods, Michael Islas

Electronic Theses and Dissertations

The goal of this thesis is to design and fabricate a DC-to-DC converter for use in high-voltage capacitor charging applications. The primary objectives include increasing the efficiency and reducing the cost of traditional methods used for this application. Traditional methods were not designed specifically for high-voltage capacitor charging and were thus very primitive and exhibited lower efficiency. Prior methods made use of a high voltage power supply and a current limiting resistor or control scheme. The power supply would often only operate efficiently at a single voltage value and would thus function poorly over a range used in charging a …

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Design And Modeling Of Radiation Hardened Lateral Power Mosfets, Matthew Landowski Jan 2009

Design And Modeling Of Radiation Hardened Lateral Power Mosfets, Matthew Landowski

Electronic Theses and Dissertations

Galactic-cosmic-rays (GCR) exist in space from unknown origins. A cosmic ray is a very high energy electron, proton, or heavy ion. As a GCR transverses a power semiconductor device, electron-hole-pairs (ehps) are generated along the ion track. Effects from this are referred to as single-event-effects (SEEs). A subset of a SEE is single-event burnout (SEB) which occurs when the parasitic bipolar junction transistor is triggered leading to thermal runaway. The failure mechanism is a complicated mix of photo-generated current, avalanche generated current, and activation of the inherent parasitic bipolar transistor. Current space-borne power systems lack the utility and advantages of …

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Simulation Of Brightness Temperatures For The Microwave Radiometer On The Aquarius/Sac-D Mission., Salman Khan Jan 2009

Simulation Of Brightness Temperatures For The Microwave Radiometer On The Aquarius/Sac-D Mission., Salman Khan

Electronic Theses and Dissertations

Microwave radiometers are highly sensitive receivers capable of measuring low levels of natural blackbody microwave emissions. Remote sensing by satellite microwave radiometers flying on low-earth, polar orbiting, satellites can infer a variety of terrestrial and atmospheric geophysical parameters for scientific and operational applications, such as weather and climate prediction. The objective of this thesis is to provide realistic simulated ocean brightness temperatures for the 3-channel Microwave Radiometer (MWR), which will be launched in May 2010 on the joint NASA/CONAE Aquarius/SAC-D Mission. These data will be used for pre-launch geophysical retrieval algorithms development and validation testing. Analyses are performed to evaluate …

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Characterization Of An Inline Row Impingement Channel For Turbine Blade Cooling Applications, Mark Ricklick Jan 2009

Characterization Of An Inline Row Impingement Channel For Turbine Blade Cooling Applications, Mark Ricklick

Electronic Theses and Dissertations

Gas turbines have become an intricate part of today's society. Besides powering practically all 200,000+ passenger aircraft in use today, they are also a predominate form of power generation when coupled with a generator. The fact that they are highly efficient, and capable of large power to weight ratios, makes gas turbines an ideal solution for many power requirement issues faced today. Designers have even been able to develop small, micro-turbines capable of producing efficient portable power. Part of the turbine's success is the fact that their efficiency levels have continuously risen since their introduction in the early 1800's. Along …

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The Integrated User Experience Evaluation Model: A Systematic Approach To Integrating User Experience Data Sources, Roberto Champney Jan 2009

The Integrated User Experience Evaluation Model: A Systematic Approach To Integrating User Experience Data Sources, Roberto Champney

Electronic Theses and Dissertations

Evaluating the user experience (UX) associated with product interaction is a challenge for current human-systems developers. This is largely due to a lack of theoretical guidance for directing how best to assess the UX and a paucity of tools to support such evaluation. This dissertation provided a framework and tools for guiding and supporting evaluation of the user experience. This doctoral research involved reviewing the literature on UX, using this knowledge to build first build a theoretical model of the UX construct and later develop a theoretical model to for the evaluation of UX in order to aid evaluators – …

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Response Sensitivity Of Highway Bridges To Random Multi-Component Earthquake Excitation, Kyle Cronin Jan 2009

Response Sensitivity Of Highway Bridges To Random Multi-Component Earthquake Excitation, Kyle Cronin

Electronic Theses and Dissertations

Highway bridges provide a critical lifeline during extreme seismic events and must maintain serviceability under a large range of earthquake intensities. Consequently, the advent of more computational power has allowed more advanced analysis approaches for predicting performance and vulnerability of highway bridges under these seismic loads. In traditional two-dimensional finite element analyses, it has been demonstrated that the incidence angle of the ground motion can play a significant role in structural response. As three-dimensional nonlinear time history analyses are used more frequently in practice, ground motions are still usually applied along a single bridge axis. It is unknown how three …

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Holiday Shores Stormwater Retrofitting Project, Stormwater Academy Jan 2009

Holiday Shores Stormwater Retrofitting Project, Stormwater Academy

BMP Trains Research and Publications

No abstract provided.

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Presence-Dependent Performance Differences Between Virtual Simulations And Miniature Worlds, Andre Huthmann Jan 2009

Presence-Dependent Performance Differences Between Virtual Simulations And Miniature Worlds, Andre Huthmann

Electronic Theses and Dissertations

The purpose of simulation is to avoid reality-based constraints by the implemen-tation of a synthetic model. Based on this advantage, interactive simulations have conquered all areas of applications from acquisition, and training, to research. Simulation results are transferred in many ways into reality and conclusions are drawn from the simulation to the application. Many anecdotal observations on human-in-the-loop simulations have shown a significant difference in actor behavior between simulations and reality-based applications. It seems that the factors that makes simulation so attractive, namely the absence of constraints and especially of imminent danger for persons and equipment, influence the behavior and …

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Numerical Study Of Encapsulated Phase Change Material (Epcm) Slurry Flow In Microchannels, Sarada Kuravi Jan 2009

Numerical Study Of Encapsulated Phase Change Material (Epcm) Slurry Flow In Microchannels, Sarada Kuravi

Electronic Theses and Dissertations

Heat transfer and flow characteristics of phase change material slurry flow in microchannels with constant heat flux at the base were investigated. The phase change process was included in the energy equation using the effective specific heat method. A parametric study was conducted numerically by varying the base fluid type, particle concentration, particle size, channel dimensions, inlet temperature, base heat flux and melting range of PCM. The particle distribution inside the microchannels was simulated using the diffusive flux model and its effect on the overall thermal performance of microchannels was investigated. Experimental investigation was conducted in microchannels of 101 [micro]m …

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Falconet: Force-Feedback Approach For Learning From Coaching And Observation Using Natural And Experiential Training, Gary Stein Jan 2009

Falconet: Force-Feedback Approach For Learning From Coaching And Observation Using Natural And Experiential Training, Gary Stein

Electronic Theses and Dissertations

Building an intelligent agent model from scratch is a difficult task. Thus, it would be preferable to have an automated process perform this task. There have been many manual and automatic techniques, however, each of these has various issues with obtaining, organizing, or making use of the data. Additionally, it can be difficult to get perfect data or, once the data is obtained, impractical to get a human subject to explain why some action was performed. Because of these problems, machine learning from observation emerged to produce agent models based on observational data. Learning from observation uses unobtrusive and purely …

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Phase-Field Simulation Of Microstructural Development Induced By Interdiffusion Fluxes Under Multiple Gradients, Rashmi Mohanty Jan 2009

Phase-Field Simulation Of Microstructural Development Induced By Interdiffusion Fluxes Under Multiple Gradients, Rashmi Mohanty

Electronic Theses and Dissertations

The diffuse-interface phase-field model is a powerful method to simulate and predict mesoscale microstructure evolution in materials using fundamental properties of thermodynamics and kinetics. The objective of this dissertation is to develop phase-field model for simulation and prediction of interdiffusion behavior and evolution of microstructure in multiphase binary and ternary systems under composition and/or temperature gradients. Simulations were carried out with emphasis on multicomponent diffusional interactions in single-phase system, and microstructure evolution in multiphase systems using thermodynamics and kinetics of real systems such as Ni-Al and Ni-Cr-Al. In addition, selected experimental studies were carried out to examine interdiffusion and microstructure …

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Estuarine Influence On Tidally Driven Circulation In The South Atlantic Bight, Peter Bacopoulos Jan 2009

Estuarine Influence On Tidally Driven Circulation In The South Atlantic Bight, Peter Bacopoulos

Electronic Theses and Dissertations

A high-resolution, finite element-based, shallow water equation model is developed to simulate the tides in the South Atlantic Bight. The model is constructed to include all of the estuarine features along the southeastern United States seaboard: coastal inlets, rivers and tidal creeks, sounds and lagoons, intertidal zones including salt marshes and mangrove swamps, and the Atlantic Intracoastal Waterway. The estuaries are represented in the finite element mesh using triangular elements with side lengths on the order of tens of meters. Also incorporated into the model is a spatially distributed bottom friction parameterization, based on the various landcover and benthic characteristics …

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Flexural Mechanical Durability Of Concrete Beams Strengthened By Externally Bonded Carbon Fiber Reinforced Polymer Sheets, Michael Olka Jan 2009

Flexural Mechanical Durability Of Concrete Beams Strengthened By Externally Bonded Carbon Fiber Reinforced Polymer Sheets, Michael Olka

Electronic Theses and Dissertations

About 77,600 bridges throughout the United States in the Federal Highway Association (FHWA) bridge database are listed as structurally deficient. This has created a need to either replace or strengthen bridges quickly and efficiently. Due to high costs for total replacement of deficient bridges, strengthening of existing bridges is a more economical alternative. A technique that has been developing over the past two decades is the strengthening of bridges using carbon fiber reinforced polymer (CFRP) sheets. The CFRP sheets are attached to the bottom of the bridge girders using structural adhesives so that the CFRP becomes an integral part of …

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On The Nature Of The Flow In A Separated Annular Diffuser, Jason Dunn Jan 2009

On The Nature Of The Flow In A Separated Annular Diffuser, Jason Dunn

Electronic Theses and Dissertations

The combustor-diffuser system remains one of the most studied sections of the turbomachine. Most of these investigations are due to the fact that quite a bit of flow diffusion is required in this section as the high speed flow exits the compressor and must be slowed down to enter the combustor. Like any diffusion process there is the chance for the development of an unfavorable adverse pressure gradient that can lead to flow separation; a cause of drastic losses within a turbine. There are two diffusion processes in the combustor-diffuser system: The flow first exits the compressor into a pre-diffuser, …

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Multifunctional Nanocomposites For High Damping Performance, Lee Algozzini Jan 2009

Multifunctional Nanocomposites For High Damping Performance, Lee Algozzini

Electronic Theses and Dissertations

Composite structures for aerospace and wind turbine applications are subjected to high acoustic and vibrational loading and exhibit very high amplitude displacements and thus premature failure. Materials with high damping or absorbing properties are crucially important to extend the life of structures. Traditional damping treatments are based on the combinations of viscoelastic, elastomeric, magnetic, and piezoelectric materials. In this work, the use of carbon nanofibers (CNFs) in the form of interconnected self-supportive paper as reinforcement can significantly improve damping performance. The interfacial friction is the primary source of energy dissipation in CNF paper based nanocomposites. The approach entailed making CNF …

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Molecular Dynamics Study Of Thermal Conductivity Enhancement Of Water Based Nanofluids, Parveen Sachdeva Jan 2009

Molecular Dynamics Study Of Thermal Conductivity Enhancement Of Water Based Nanofluids, Parveen Sachdeva

Electronic Theses and Dissertations

A systematic investigation using molecular dynamics (MD) simulation involving particle volume fraction, size, wettability and system temperature is performed and the effect of these parameters on the thermal conductivity of water based nanofluids is discussed. Nanofluids are a colloidal suspension of 10 -100 nm particles in base fluid. In the last decade, significant research has been done in nanofluids, and thermal conductivity increases in double digits were reported in the literature. This anomalous increase in thermal conductivity cannot be explained by classical theories like Maxwell's model and Hamilton-Crosser model for nanoparticle suspensions. Various mechanisms responsible for thermal conductivity enhancement in …

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Thermo-Mechanical Characterization Of High-Temperature Shape Memory Ni-Ti-Pd Wires, Matthew Fox Jan 2009

Thermo-Mechanical Characterization Of High-Temperature Shape Memory Ni-Ti-Pd Wires, Matthew Fox

Electronic Theses and Dissertations

Actuator applications of shape memory alloys have typically been limited by their phase transformation temperatures to around 100 degrees C. However, recently with a focus on aerospace and turbomachinery applications there have been successful efforts to increase the phase transformation temperatures. Several of these alloy development efforts have involved ternary and quaternary elemental additions (e.g., Pt, Pd, etc.) to binary NiTi alloys. Experimentally assessing the effects of varying composition and thermo-mechanical processing parameters can be cost intensive, especially when expensive, high-purity elemental additions are involved. Thus, in order to save on development costs there is value in establishing a methodology …

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Contributions By Individual And Group Strategies For Organizational Learning In Architectural, Engineering, And Construction Firms, Robert Beaver Jan 2009

Contributions By Individual And Group Strategies For Organizational Learning In Architectural, Engineering, And Construction Firms, Robert Beaver

Electronic Theses and Dissertations

Organizations with multiple operating requirements require support functions to assist in execution of strategic goals. This effort, in turn, requires management of engineering activities in control of projects and in sustaining facilities. High level strategies include employing engineering support that consists of a project management function encompassing technical and managerial disciplines. The architecture/engineering, and construction office (AEC) is the subject of this research. Engineering and construction oriented organizations have experienced challenges to their abilities to learn and grow. This has potential detrimental implications for these organizations if support functions cannot keep pace with changing objectives and strategy. The competitive nature …

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A Systematic Analysis To Identify, Mitigate, Quantify, And Measure Risk Factors Contributing To Falls In Nasa Ground Support Ope, Joylene Ware Jan 2009

A Systematic Analysis To Identify, Mitigate, Quantify, And Measure Risk Factors Contributing To Falls In Nasa Ground Support Ope, Joylene Ware

Electronic Theses and Dissertations

The objective of the research was to develop and validate a multifaceted model such as a fuzzy Analytical Hierarchy Process (AHP) model that considers both qualitative and quantitative elements with relative significance in assessing the likelihood of falls and aid in the design of NASA Ground Support Operations in aerospace environments. The model represented linguistic variables that quantified significant risk factor levels. Multiple risk factors that contribute to falls in NASA Ground Support Operations are task related, human/personal, environmental, and organizational. Six subject matter experts were asked to participate in a voting system involving a survey where they judge risk …

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Dense Spectral Beam Combining With Volume Bragg Gratings In Photo-Thermo-Refractive Glass, Oleksiy Andrusyak Jan 2009

Dense Spectral Beam Combining With Volume Bragg Gratings In Photo-Thermo-Refractive Glass, Oleksiy Andrusyak

Electronic Theses and Dissertations

Beam combining techniques have become an important tool in the design of high-power high-brightness laser systems. Spectral beam combining (SBC) is an incoherent combining technique that does not require phase control of sources, allowing for a stable and robust system. Using SBC, beams from an array of lasers with each element operated at a different wavelength are combined into a single near-diffraction-limited beam with the same aperture using dispersive optical elements. SBC by means of volume Bragg gratings (VBGs) utilizes unique spectral response of VBGs: diffraction efficiency is close to unity when the Bragg condition is satisfied and is close …

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Analysis And Design Of Wide-Angle Foveated Optical Systems, George Curatu Jan 2009

Analysis And Design Of Wide-Angle Foveated Optical Systems, George Curatu

Electronic Theses and Dissertations

The development of compact imaging systems capable of transmitting high-resolution images in real-time while covering a wide field-of-view (FOV) is critical in a variety of military and civilian applications: surveillance, threat detection, target acquisition, tracking, remote operation of unmanned vehicles, etc. Recently, optical foveated imaging using liquid crystal (LC) spatial light modulators (SLM) has received considerable attention as a potential approach to reducing size and complexity in fast wide-angle lenses. The fundamental concept behind optical foveated imaging is reducing the number of elements in a fast wide-angle lens by placing a phase SLM at the pupil stop to dynamically compensate …

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Scheduling And Resource Management For Complex Systems: From Large-Scale Distributed Systems To Very Large Sensor Networks, Chen Yu Jan 2009

Scheduling And Resource Management For Complex Systems: From Large-Scale Distributed Systems To Very Large Sensor Networks, Chen Yu

Electronic Theses and Dissertations

In this dissertation, we focus on multiple levels of optimized resource management techniques. We first consider a classic resource management problem, namely the scheduling of data-intensive applications. We define the Divisible Load Scheduling (DLS) problem, outline the system model based on the assumption that data staging and all communication with the sites can be done in parallel, and introduce a set of optimal divisible load scheduling algorithms and the related fault-tolerant coordination algorithm. The DLS algorithms introduced in this dissertation exploit parallel communication, consider realistic scenarios regarding the time when heterogeneous computing systems are available, and generate optimal schedules. Performance …

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Control Of Nonh=Holonomic Systems, Hongliang Yuan Jan 2009

Control Of Nonh=Holonomic Systems, Hongliang Yuan

Electronic Theses and Dissertations

Many real-world electrical and mechanical systems have velocity-dependent constraints in their dynamic models. For example, car-like robots, unmanned aerial vehicles, autonomous underwater vehicles and hopping robots, etc. Most of these systems can be transformed into a chained form, which is considered as a canonical form of these nonholonomic systems. Hence, study of chained systems ensure their wide applicability. This thesis studied the problem of continuous feed-back control of the chained systems while pursuing inverse optimality and exponential convergence rates, as well as the feed-back stabilization problem under input saturation constraints. These studies are based on global singularity-free state transformations and …

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Analysis Of The Physical Forcing Mechanisms Influencing Salinity Transport For The Lower St. Johns River, Derek Giardino Jan 2009

Analysis Of The Physical Forcing Mechanisms Influencing Salinity Transport For The Lower St. Johns River, Derek Giardino

Electronic Theses and Dissertations

The focus of this thesis is the forcing mechanisms incorporated with salinity transport for the Lower St. Johns River. There are two primary analyses performed: a historical data analysis of primary forcing mechanisms to determine the importance of each individual influence, and a tidal hydrodynamics analysis for the Lower St. Johns River to determine the required tidal constituents for an accurate resynthesis. This thesis is a preliminary effort in understanding salinity transport for the Lower St. Johns River for engineering projects such as the dredging of navigation canals and freshwater withdrawal from the river. The analysis of the physical forcing …

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