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Title: Evaluation of Water Degradation ofPolymer Matrix Composites by Micromechanical and Macromechanical Tests.
Creator: Ramirez, Felipe A., Carlsson, Leif A., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Degradation of the critical components of polymer matrix composites in marine environments had been experimentally investigated. Water absorption behavior of neat resin and composite specimens was examined. The tensile strength of fibers was monitored using the single filament test. The mechanical properties of the resins were monitored by tensile, flexure, and dynamic-mechanical tests. In addition, matrix shrinkage during cure and matrix swelling after immersion in water were monitored. The...
Show moreDegradation of the critical components of polymer matrix composites in marine environments had been experimentally investigated. Water absorption behavior of neat resin and composite specimens was examined. The tensile strength of fibers was monitored using the single filament test. The mechanical properties of the resins were monitored by tensile, flexure, and dynamic-mechanical tests. In addition, matrix shrinkage during cure and matrix swelling after immersion in water were monitored. The integrity of the fiber/matrix (F/M) interface of the composite systems was studied using the single fiber fragmentation test (SFFT). Macroscopic composites were examined using transverse tensile and transverse flexure tests to study the influence of the integrity of the matrix and F/M interface on the macroscopic response. In addition, for characterization of F/M debonding in the SFFT, a fracture mechanics model and modified test procedure were developed.
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Date Issued: 2008
PURL: http://purl.flvc.org/fau/fd/FA00012543
Subject Headings: Composite materials--Mechanical properties, Polymeric composites--Testing, Fibrous composites--Testing, Polymers--Deterioration
Format: Document (PDF)

Title: Determining anchoring systems for marine renewable energy devices moored in a western boundary current.
Creator: Seibert, Michael G., Charles E. Schmidt College of Science, Department of Ocean and Mechanical Engineering
Abstract/Description: In this thesis anchoring systems for marine renewable energy devices are examined for an area of interest off the coast of Southeast Florida that contains both ocean current and thermal resources for future energy extraction. Bottom types observed during previous regional benthic surveys are compiled and anchor performance of each potential anchor type for the observed bottom types is compared. A baseline range of environmental conditions is created by combining local current measurements and...
Show moreIn this thesis anchoring systems for marine renewable energy devices are examined for an area of interest off the coast of Southeast Florida that contains both ocean current and thermal resources for future energy extraction. Bottom types observed during previous regional benthic surveys are compiled and anchor performance of each potential anchor type for the observed bottom types is compared. A baseline range of environmental conditions is created by combining local current measurements and offshore industry standards. Numerical simulations of single point moored marine hydrokinetic devices are created and used to extract anchor loading for two potential deployment locations, multiple mooring scopes, and turbine rotor diameters up to 50 m. This anchor loading data is used for preliminary anchor sizing of deadweight and driven plate anchors on both cohesionless and cohesive soils. Finally, the capabilities of drag embedment and pile anchors relevant to marine renewable energy devices are discussed.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3172697
Subject Headings: Ocean energy resources, Renewable energy sources, Deep-sea moorings, Ocean engineering, Geothermal energy
Format: Document (PDF)

Title: High-Frequency Underwater Acoustic Propagation in a Port Modeled as a Three-Dimensional Duct Closed at One End Using the Method of Images.
Creator: Beaujean, Pierre-Philippe J., Staska, Matthew D.
Date Issued: 2012-06-03
PURL: http://purl.flvc.org/fau/flvc_fau_islandoraimporter_10.1155_2012_929174_1632168479
Format: Citation

Title: Electrochemical aspects of magnetohydrodynamic thrusters.
Creator: Moreno, Juan E., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The concept of using Magnetohydrodynamics to provide thrust has been around for decades. However little work has been carried out in one of the fundamental aspects that allows for these systems to operate in seawater. Therefore a series of tests were carried out to determine how the electrochemical reactions occurring at the electrodes affect the seawater system. These tests were used to determine the effects magnetic fields have on seawater conductivity, the pH changes around the electrodes,...
Show moreThe concept of using Magnetohydrodynamics to provide thrust has been around for decades. However little work has been carried out in one of the fundamental aspects that allows for these systems to operate in seawater. Therefore a series of tests were carried out to determine how the electrochemical reactions occurring at the electrodes affect the seawater system. These tests were used to determine the effects magnetic fields have on seawater conductivity, the pH changes around the electrodes, and consider the double layer capacitance model as a means to decrease the amount of gas bubbles created at the electrodes. As a result significant increases in resistivity in seawater were observed when the magnetic field was introduced, pH changes were seen on both the cathode and anode, and pulsing of the applied potential may stimulate further work to be considered.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3171720
Subject Headings: Electric power production, Metrohydrodynamic generation, Fluid mechanics, Magnetohydrodynamics
Format: Document (PDF)

Title: Modeling of linear induction machines for analysis and control.
Creator: Sinisterra, Armando Jose, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: In this thesis, the analysis of the dynamic response of a Linear Induction Motor as an electromechanical system is done, accounting for all the governing equations implied in the process which are used to develop the corresponding simulation models. Once this model is presented, a feedback control system is implemented in order to analyze the controlled response of the motor, considering the applications and conditions analogue to aircraft launcher systems. Also a comparison between the...
Show moreIn this thesis, the analysis of the dynamic response of a Linear Induction Motor as an electromechanical system is done, accounting for all the governing equations implied in the process which are used to develop the corresponding simulation models. Once this model is presented, a feedback control system is implemented in order to analyze the controlled response of the motor, considering the applications and conditions analogue to aircraft launcher systems. Also a comparison between the Linear and Rotary induction motors describing the differences, similarities and equivalences will be developed.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3172944
Subject Headings: Electric motors, Induction, Mathematical models, Electric propulsion, Control theory
Format: Document (PDF)

Title: Pitting potential of high performance duplex stainless steels reinforcements.
Creator: Sanchez, Erika Maria., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A cyclic polarization procedure was designed to evaluate the pitting potentials of high performance stainless steels in synthetic concrete pore water at different chloride concentrations. Cyclic polarization scans were performed on high performance stainless steel reinforcements, S32201, S32305 and S32205. Pitting initiation was observed below the oxygen evolution potential for high chloride concentrations. S32201 and S32304 showed the presence of metastable pitting before reaching its...
Show moreA cyclic polarization procedure was designed to evaluate the pitting potentials of high performance stainless steels in synthetic concrete pore water at different chloride concentrations. Cyclic polarization scans were performed on high performance stainless steel reinforcements, S32201, S32305 and S32205. Pitting initiation was observed below the oxygen evolution potential for high chloride concentrations. S32201 and S32304 showed the presence of metastable pitting before reaching its pitting potential. Pitting resistance performance, based on cyclic polarization, was consistent with each material's respective Pitting Resistance Equivalent Number (PREN) value. For S32201 and S32304, pitting potential decreased as the chloride concentration increased, whereas S32205 did not pit at the chloride concentrations tested.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3334100
Subject Headings: Reinforced concrete construction, Steel, Structural, Testing, Corrosion and anti-corrosives
Format: Document (PDF)

Title: Very high frequency MIMO underwater acoustic communications in ports and shallow waters.
Creator: Real, Gaultier., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis presents the development of a Multiple-Input Multiple-Output (MIMO) capable high bit rate acoustic modem operating at high frequencies. A MIMO channel estimation technique based on Least-Squares (LS) estimation is developed here. Channel deconvolution is completed using a Minimum Mean-Square Error (MMSE) Linear Equalizer (LE). An Interference Cancellation Linear Equalizer (ICLE) is used to provide the theoretical limit of the MIMO deconvolution process. The RMSE of the channel...
Show moreThis thesis presents the development of a Multiple-Input Multiple-Output (MIMO) capable high bit rate acoustic modem operating at high frequencies. A MIMO channel estimation technique based on Least-Squares (LS) estimation is developed here. Channel deconvolution is completed using a Minimum Mean-Square Error (MMSE) Linear Equalizer (LE). An Interference Cancellation Linear Equalizer (ICLE) is used to provide the theoretical limit of the MIMO deconvolution process. The RMSE of the channel estimation process was 1.83 % and 6.1810 %, respectively for simulated and experimental data. Using experimental data, the RMSE before MIMO deconvolution process was 141.3 % and dropped down to 60.224 % and to 4.4545 %, respectively after LE and ICLE. At raw reception, the RMSE was 101.83 % and dropped down to 9.36 % and to 1.86 % using respectively LE and ICLE with simulated data.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3333309
Subject Headings: MIMO systems, Wireless communication systems, Underwater acoustics, Fluid dynamics
Format: Document (PDF)

Title: The directionality of noise created by turbulent flow over roughness.
Creator: Kaufman, Gerard P., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Flow over a rough surface is known to radiate sound as a dipole source that is directional. In order to better understand this source, measurements are being made in a wind tunnel using a microphone array. The measurements collected by a microphone array are beamformed to give a source image and can be deconvolved with an assumed point spread function in order to obtain the source levels. This thesis considers alternative analysis algorithms that can be used to analyze wind tunnel data. Only...
Show moreFlow over a rough surface is known to radiate sound as a dipole source that is directional. In order to better understand this source, measurements are being made in a wind tunnel using a microphone array. The measurements collected by a microphone array are beamformed to give a source image and can be deconvolved with an assumed point spread function in order to obtain the source levels. This thesis considers alternative analysis algorithms that can be used to analyze wind tunnel data. Only numerical examples of how these algorithms work will be presented and the analysis of real data will be considered in later studies. It will be shown how estimates can be made of the source directivity by comparing the measured data with a theoretical source model and minimizing the error between the model and the measurements.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3171394
Subject Headings: Electromagnetic fields, Signal processing, Digital techniques, Noise control, Adaptive signal processing, Acoustic emission, Measurement
Format: Document (PDF)

Title: Automated Launch and Recovery of an Autonomous Underwater Vehicle from an Unmanned Surface Vessel.
Creator: Sarda, Edoardo I, Dhanak, Manhar R., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Research on collaboration among unmanned platforms is essential to improve the applications for autonomous missions, by expanding the working environment of the robotic systems, and reducing the risks and the costs associated with conducting manned operations. This research is devoted to enable the collaboration between an Unmanned Surface Vehicle (USV) and an Autonomous Underwater Vehicle (AUV), by allowing the first one to launch and recover the second one. The objective of this...
Show moreResearch on collaboration among unmanned platforms is essential to improve the applications for autonomous missions, by expanding the working environment of the robotic systems, and reducing the risks and the costs associated with conducting manned operations. This research is devoted to enable the collaboration between an Unmanned Surface Vehicle (USV) and an Autonomous Underwater Vehicle (AUV), by allowing the first one to launch and recover the second one. The objective of this dissertation is to identify possible methods to launch and recover a REMUS 100 AUV from a WAM-V 16 USV, thus developing this capability by designing and implementing a launch and recovery system (LARS). To meet this objective, a series of preliminary experiments was first performed to identify two distinct methods to launch and recover the AUV: mobile and semi-stationary. Both methods have been simulated using the Orcaflex software. Subsequently, the necessary control systems to create the mandatory USV autonomy for the purpose of launch and recovery were developed. Specifically, a series of low-level controllers were designed and implemented to enable two autonomous maneuvers on the USV: station-keeping and speed & heading control. In addition, a level of intelligence to autonomously identify the optimal operating conditions within the vehicles' working environment, was derived and integrated on the USV. Lastly, a LARS was designed and implemented on the vehicles to perform the operation following the proposed methodology. The LARS and all subsystems developed for this research were extensively tested through sea-trials. The methodology for launch and recovery, the design of the LARS and the experimental findings are reported in this document.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004631, http://purl.flvc.org/fau/fd/FA00004631
Subject Headings: Underwater acoustic telemetry., Fuzzy systems., Nonlinear control theory., Adaptive signal processing., Oceanographic submersibles--Automatic control., Submersibles--Control systems.
Format: Document (PDF)

Title: Analyzing the effect of fin morphology on the propulsive performance of an oscillating caudal fin using a robotic model.
Creator: Fischer, Tyler M., Curet, Oscar M., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A bio-inspired robotic underwater vessel was developed to test the effect of fin morphology on the propulsive performance of caudal fin. The robotic vessel, called The Bullet Fish, features a cylindrical body with a hemisphere at the forward section and a conical body at the stern. The vessel uses an oscillating caudal fin for thrust generation. The robotic vessel was tested in a recirculating flume for seven different caudal fins that range different bio-inspired forms and aspect ratios. The...
Show moreA bio-inspired robotic underwater vessel was developed to test the effect of fin morphology on the propulsive performance of caudal fin. The robotic vessel, called The Bullet Fish, features a cylindrical body with a hemisphere at the forward section and a conical body at the stern. The vessel uses an oscillating caudal fin for thrust generation. The robotic vessel was tested in a recirculating flume for seven different caudal fins that range different bio-inspired forms and aspect ratios. The experiments were performed at four different flow velocities and two flapping frequencies: 0.5 and 1.0 Hz. We found that for 1 Hz flapping frequency that in general as the aspect-ratio decreases both thrust production tends and power decrease resulting in a better propulsive efficiency for aspect ratios between 0.9 and 1.0. A less uniform trend was found for 0.5 Hz, where our data suggest multiple efficiency peaks. Additional experiments on the robotic model could help understand the propulsion aquatic locomotion and help the design of bio-inspired underwater vehicles.
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Date Issued: 2017
PURL: http://purl.flvc.org/fau/fd/FA00004944, http://purl.flvc.org/fau/fd/FA00004944
Subject Headings: Robotics., Robots--Kinematics., Artificial intelligence., Biomimetics., Bioinformatics., Stereotypes (Social psychology)
Format: Document (PDF)

Title: Analysis of Turbulence Observed in the Florida Current using an ADCP.
Creator: Denton, John E., Dhanak, Manhar, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The observation of turbulence in the Florida Current is presented with the use of velocity measurements collected with an Acoustic Doppler Current Profiler (ADCP). The research is conducted through application of the theories of Taylor and Kolmogorov and related derivations, and processing tools of MATLAB software to this Eulerian observation of flow [1]. The velocity profile of the Florida Current is deduced in terms of its turbulent character with shear, acceleration, gradient, Reynolds...
Show moreThe observation of turbulence in the Florida Current is presented with the use of velocity measurements collected with an Acoustic Doppler Current Profiler (ADCP). The research is conducted through application of the theories of Taylor and Kolmogorov and related derivations, and processing tools of MATLAB software to this Eulerian observation of flow [1]. The velocity profile of the Florida Current is deduced in terms of its turbulent character with shear, acceleration, gradient, Reynolds Number, Reynolds Stress, Welch power spectrum density of current velocity, wavenumbers of Taylor’s hypothesis and Kolmogorov, wavenumber spectrum, eddy diameters, diapycnal diffusivity, and the Richardson Number. Processing methods are validated with results of other research conducted in the Florida Current with the use of a Multi-Scale Profiler, and an Advanced Microstructure Profiler for determination of shear, dissipation, diffusivity, and estimates of turbulent eddy diameters based on Taylor’s Hypothesis [1][4]. A spectral analysis is developed and is compared with Kolmogorov’s -5/3-Law. The process and the results of the analysis are described.
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Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00013173
Subject Headings: Florida Current, Turbulence--Measurement, Underwater acoustics--Data processing, Doppler effect
Format: Document (PDF)

Title: A Hybrid System for Simulation of Athletic Activities Related to Lower Extremity Biomechanics.
Creator: Trepeck, Cameron, Hashemi, Javad, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: In this dissertation, the design and development of a hybrid robotic system that simulates dynamic biomechanical tasks of the lower extremity with emphasis on knee and hip joints are presented. The hybrid system utilizes a mechanical hip and a cadaveric knee/ankle component and can accelerate the whole complex towards the ground. This system is used to simulate complex athletic movements such as landing from a jump at various anatomical orientations of the lower extremity with muscle action....
Show moreIn this dissertation, the design and development of a hybrid robotic system that simulates dynamic biomechanical tasks of the lower extremity with emphasis on knee and hip joints are presented. The hybrid system utilizes a mechanical hip and a cadaveric knee/ankle component and can accelerate the whole complex towards the ground. This system is used to simulate complex athletic movements such as landing from a jump at various anatomical orientations of the lower extremity with muscle action. The dynamic response of the lower extremity is monitored and analyzed during impulsive contact between the ground and the cadaveric leg. The cadaveric knee is instrumented to measure strain of the Anterior Cruciate Ligament (ACL) during simulated high impact sports activities. The mechanical hip allows various kinematics of the hip including flexion as well as abduction. In addition to the flexion and abduction of the mechanical hip, the controlled flexion and extension of the cadaveric knee allows for simulation of complex tasks such as landing from a jump. A large number of tests were performed at various anatomical positions utilizing this device to simulate landing from a jump. ACL strain was measured during these tasks using a Differential Variance Resistance Transducer (DVRT). Ground Reaction Force and muscle forces were measured and monitored using AmCell load cells recorded using the LabView software. one-inch and 6-inch jump landing heights were used for all the simulations. The tests were performed at differing angles of hip flexion (0°, 30°, 45°, 60°) and at two different ankle positions. Plantar flexion and flat-footed landing conditions were simulated and compared in all degrees of hip flexion. These tests were repeated with and without hip abduction in order to study the effects of these landing positions on ACL strain. Hip flexion was found to effect ACL strain: as angle of hip flexion increases, ACL strain decreases. This occurred in both abducted and non-abducted hip positions. Ankle landing position had an effect only in small drop heights, while hip abduction had an effect in large drops. Future tests must be completed to further study these effects. These studies showed that the robotic system can simulate dynamic tasks, apply muscle forces, and move the cadaveric tissue in three dimensional biomechanical positions.
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Date Issued: 2017
PURL: http://purl.flvc.org/fau/fd/FA00004898, http://purl.flvc.org/fau/fd/FA00004898
Subject Headings: Musculoskeletal system--Wounds and injuries., Musculoskeletal system--Mechanical properties., Biomechanics--Computer simulation., Human mechanics., Artificial joints.
Format: Document (PDF)

Title: A direct thrust measurement system for a waterjet propelled, free running USV.
Creator: Grimes, John A., von Ellenrieder, Karl, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The relationship between cross-flow at a waterjet inlet and delivered thrust is not fully understood. A direct thrust measurement system was designed for a waterjet propelled, free running USV. To induce sway velocity at the waterjet inlet, which was considered equivalent to the cross flow, circles of varying radii were performed at Reynolds Numbers between 3.48 x 106 and 8.7 x 106 and radii from 2.7 to 6.3 boat lengths. Sway velocities were less than twenty percent of mean forward speed with...
Show moreThe relationship between cross-flow at a waterjet inlet and delivered thrust is not fully understood. A direct thrust measurement system was designed for a waterjet propelled, free running USV. To induce sway velocity at the waterjet inlet, which was considered equivalent to the cross flow, circles of varying radii were performed at Reynolds Numbers between 3.48 x 106 and 8.7 x 106 and radii from 2.7 to 6.3 boat lengths. Sway velocities were less than twenty percent of mean forward speed with slip angles that were less than 20°. Thrust Loading Coefficients were compared to sway as a percent of forward speed. In small radius turns, no relationship was seen, while in larger radius turns, peaks of sway velocity corresponded with drops in thrust, but this was determined to be caused by reduced vehicle yaw in these intervals . Decoupling of thrust and yaw rate is recommended for future research.
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Date Issued: 2013
PURL: http://purl.flvc.org/fau/fd/FA0004023
Subject Headings: Oceanographic instruments -- Evaluation, Propellers, Ship propulsion, Ships -- Hydrodynamics, Stability of ships
Format: Document (PDF)

Title: Effects of cement alkalinity, exposure conditions and steel-concrete interface on the time-to-corrosion and chloride threshold for reinforcing steel in concrete.
Creator: Nam, Jingak., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Effects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and distribution of air voids at the steel-concrete interface on the chloride threshold and time-to-corrosion for reinforcing steel in concrete have been studied. Also, experiments were performed to evaluate effects of RH and temperature on the diffusion of chloride in concrete and develop a method for ex-situ pH...
Show moreEffects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and distribution of air voids at the steel-concrete interface on the chloride threshold and time-to-corrosion for reinforcing steel in concrete have been studied. Also, experiments were performed to evaluate effects of RH and temperature on the diffusion of chloride in concrete and develop a method for ex-situ pH measurement of concrete pore water. Once specimens were fabricated and exposed to a corrosive chloride solution, various experimental techniques were employed to determine time-to-corrosion, chloride threshold, diffusion coefficient and void density along the rebar trace as well as pore water pH. Based upon the resultant data, several findings related to the above parameters have been obtained as summarized below. First, time for the corrosion initiation was longest for G109 concrete specimens with high alkalinity cement (HA). Also, chloride threshold increased with increasing time-to-corrosion and cement alkalinity. Consequently, the HA specimens exhibited the highest chloride threshold compared to low and normal alkalinity ones. Second, high temperature and temperature variations reduced time-to-corrosion of reinforcing steel in concrete since chloride diffusion was accelerated at higher temperature and possibly by temperature variations. The lowest chloride threshold values were found for outdoor exposed specimens suggesting that variation of RH or temperature (or both) facilitated rapid chloride diffusion. Third, an elevated time-to-corrosion and chloride threshold values were found for the wire brushed steel specimens compared to as-received ones. The higher ratio of [OH-]/[Fe n+] on the wire brushed steel surface compared to that of as-received case can be the possible cause because the higher ratio of this parameter enables the formation of a more protective passive film on the rebar. Fourth, voids at the steel-concrete interface facilitated passive film breakdown and onset of localized corrosion. This tendency for corrosion initiation increased in proportion to void size irrespective of specimen type. Also, [Cl -]th decreased with increasing void diameter. In addition, new ex-situ leaching method for determining concrete pore water alkalinity was developed.
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Date Issued: 2004
PURL: http://purl.flvc.org/fcla/dt/12096
Subject Headings: Reinforced concrete construction, Chlorides, Steel--Corrosion, Composite reinforced concrete
Format: Document (PDF)

Title: Hybrid stress analysis using digitized photoelastic data and numerical methods.
Creator: Mahfuz, Hassan, Florida Atlantic University, Case, Robert O., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Equations of stress-difference elasticity, derived from the equations of equilibrium and compatibility for a two-dimensional stress field, are solved for arbitrarily digitized, singly and multiply connected domains. Photoelastic data determined experimentally along the boundary provide the boundary values for the solution of the three elliptic partial differential equations by the finite difference method. A computerized method is developed to generate grid mesh, weighting functions and nodal...
Show moreEquations of stress-difference elasticity, derived from the equations of equilibrium and compatibility for a two-dimensional stress field, are solved for arbitrarily digitized, singly and multiply connected domains. Photoelastic data determined experimentally along the boundary provide the boundary values for the solution of the three elliptic partial differential equations by the finite difference method. A computerized method is developed to generate grid mesh, weighting functions and nodal connectivity within the digitized boundary for the solution of these partial differential equations. A method is introduced to digitize the photoelastic fringes, namely isochromatics and isoclinics, and to estimate the values of sigma1 - sigma2, sigma x - sigma y and tau xy at each nodal point by an interpolation technique. Interpolated values of the stress parameters are used to improve the initial estimate and hence the convergence of the iterative solution of the system of equations. Superfluous boundary conditions are added from the digitized photoelastic data for further speeding up the rate of convergence. The boundary of the domain and the photoelastic fringes are digitized by physically traversing the cursor along the boundary, and the digitized information is scanned horizontally and vertically to generate internal and boundary nodal points. A linear search determines the nodal connectivity and isolates the boundary points for the input of the boundary values. A similar scanning method estimates the photoelastic parameters at each nodal point and also finds the points closest to the tint of passage of each photoelastic fringe. Stress values at these close points are determined without interpolation and are subsequently used as superfluous boundary conditions in the iteration scheme. Successive over-relaxation is applied to the classical Gauss-Seidel method for final enhancement of the convergence of the iteration process. The iteration scheme starts with an accelerating factor other than unity and estimates the spectral radius of the iteration matrix from the two vector norms. This information is used to estimate a temporary value of the optimum relaxation parameter, omega[opt], which is used for a fixed number of iterations to approximate a better value of the accelerating factor. The process is continued until two successive estimates differ by a given tolerance or the stopping criteria are reached. Detailed techniques of developing the code for mesh generation, photoelastic data collection and boundary value interpolation to solve the elliptic boundary value problems are presented. Three separate examples with varying stress gradients and fringe patterns are presented to test the validity of the code and the overall method. Results are compared with the analytical and experimental solutions, and the significant improvement in the rate of convergence is demonstrated.
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Date Issued: 1989
PURL: http://purl.flvc.org/fcla/dt/11934
Subject Headings: Strains and stresses, Photoelasticity, Numerical analysis--Data processing
Format: Document (PDF)

Title: A Low-Level USV Controller Incorporating an Environmental Disturbance Observer.
Creator: Diddams, Michael Albert, Dhanak, Manhar R., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Modeling, system identification and controller design for a 16’ catamaran is described with the objective of enhanced operation in the presence of environmental disturbances including wind, waves and current. The vehicle is fully-actuated in surge, sway and yaw degrees of freedom. Analytical and experimental system identification is carried out to create a numerical model of the vehicle. A composite system of a Multiinput multi-output Proportional-Derivative (PD) controller and a nonlinear...
Show moreModeling, system identification and controller design for a 16’ catamaran is described with the objective of enhanced operation in the presence of environmental disturbances including wind, waves and current. The vehicle is fully-actuated in surge, sway and yaw degrees of freedom. Analytical and experimental system identification is carried out to create a numerical model of the vehicle. A composite system of a Multiinput multi-output Proportional-Derivative (PD) controller and a nonlinear disturbance observer is used for station-keeping and transiting modes of operation. A waypoint transiting algorithm is developed to output heading and cross-track error from vehicle position and waypoints. A control allocation method is designed to lower azimuthing frequency and incorporate angle saturation and rate limits. Validation is achieved with improvement in simulation with the addition of the nonlinear observer.
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Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00013022
Subject Headings: Unmanned surface vehicles, Environmental disturbances, Catamarans--Design and construction
Format: Document (PDF)

Title: Calibration and Performance Evaluation for a Multiple Overlapping Field of View Serial Laser Imager.
Creator: Rasoletti, Nicholas, Beaujean, Pierre-Philippe, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The Combined Laser and Scan Sonar (CLASS) system is an extended range imaging system, incorporating both high-resolution laser images and high frequency sonar images. Both the laser and sonar images are collected simultaneously during testing to provide dual mode imagery of an underwater target, displaying both a 2D image of the target (laser image) and a 3D overlay of the target (sonar image). The laser component of the system is a Multiple Overlapping Field of view Serial Laser Imager ...
Show moreThe Combined Laser and Scan Sonar (CLASS) system is an extended range imaging system, incorporating both high-resolution laser images and high frequency sonar images. Both the laser and sonar images are collected simultaneously during testing to provide dual mode imagery of an underwater target, displaying both a 2D image of the target (laser image) and a 3D overlay of the target (sonar image). The laser component of the system is a Multiple Overlapping Field of view Serial Laser Imager (MOFSLI), capable of generating high-resolution sub-centimeter 2D images. MOFSLI generates the images by way of a near diffraction-limited 532 [nm] continuous wave (CW) laser beam being scanned over the target. Initial field tests resulted in high-quality images of the ocean floor, but also indicated the need for additional research on MOFSLI. In this thesis, we focus on the calibration of MOFSLI and on the evaluation of the image quality generated by this system, as a function of range, source power, receiver gain and water turbidity. This work was completed in the specialized underwater electrooptics testing facility located in the Ocean Visibility and Optics laboratory at Harbor Branch Oceanographic Institute (HBOI). Laboratory testing revealed the operational limits of the system, which functioned well until just beyond five attenuation lengths, where it becomes contrast limited due attenuation of target signal and the collection of non-image bearing backscattered photons. Testing also revealed the optimal settings of the system at given environmental conditions.
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Date Issued: 2015
PURL: http://purl.flvc.org/fau/fd/FA00004538, http://purl.flvc.org/fau/fd/FA00004538
Subject Headings: Electrooptics, Inertial navigation systems, Lasers -- Measurement -- Evaluation, Light -- Scattering
Format: Document (PDF)

Title: Bulk diffusion of high performance concrete specimens exposed to different levels of sodium chloride and seawater.
Creator: Arias, Wendy J., Presuel-Moreno, Francisco, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The purpose of this study was to investigate the performance to chloride penetration of specimens made with three base compositions (three different supplementary cementitious materials) and water to cementitious ratios of 0.35, 0.41, or 0.47. The specimens were subjected to bulk diffusion test or full immersion. The mixes were exposed to 0.1 M, 0.6 M, or 2.8 M sodium chloride solution for different periods of time. Also, partially immersed specimens were exposed to indoor and outdoor...
Show moreThe purpose of this study was to investigate the performance to chloride penetration of specimens made with three base compositions (three different supplementary cementitious materials) and water to cementitious ratios of 0.35, 0.41, or 0.47. The specimens were subjected to bulk diffusion test or full immersion. The mixes were exposed to 0.1 M, 0.6 M, or 2.8 M sodium chloride solution for different periods of time. Also, partially immersed specimens were exposed to indoor and outdoor exposures (tidal, splash, barge). Chloride concentration profiles were obtained and the apparent diffusion coefficient was calculated. The skin effect was found only on some chloride profiles exposed to 0.1 M sodium chloride solution. The chloride binding capacity was calculated; specimens with 20% Fly Ash and 8% Silica Fume had the highest binding capacity (70.99%). The apparent diffusivity coefficient was found to be dependent on the curing regime as well as the water to cement ratio. The correlation between effective resistivity and apparent diffusion coefficient was determined.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00004076, http://purl.flvc.org/fau/fd/FA00004076
Subject Headings: Bulk solids flow, Concrete -- Corrosion, Concrete, Effect of salt on, Reinforced concrete -- Deterioration, Sustainable construction
Format: Document (PDF)

Title: Characterizing the Magnetic Signature of Internal Waves.
Creator: Nieves, Eric, Beaujean, Pierre-Philippe, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This study is performed in tandem with numerous experiments performed by the U.S. Navy to characterize the ocean environment in the South Florida region. The research performed in this study includes signal processing steps for isolating ocean phenomena, such as internal waves, in the magnetic field. Raw magnetometer signals, one on shore and one underwater, are processed and removed of common distortions. They are then run through a series of filtering techniques, including frequency domain...
Show moreThis study is performed in tandem with numerous experiments performed by the U.S. Navy to characterize the ocean environment in the South Florida region. The research performed in this study includes signal processing steps for isolating ocean phenomena, such as internal waves, in the magnetic field. Raw magnetometer signals, one on shore and one underwater, are processed and removed of common distortions. They are then run through a series of filtering techniques, including frequency domain cancellation (FDC). The results of the filtered magnetic residual are compared to similarly processed Acoustic Doppler Current Profiler (ADCP) data to correlate whether a magnetic signature is caused by ocean phenomena.
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Date Issued: 2017
PURL: http://purl.flvc.org/fau/fd/FA00004917, http://purl.flvc.org/fau/fd/FA00004917
Subject Headings: Ocean currents--Measurement., Adaptive signal processing., Wave-motion, Theory of., Wavelets (Mathematics)
Format: Document (PDF)

Title: Characterization and Modeling of Profiling Oceanographic Lidar for Remotely Sampling Ocean Optical Properties.
Creator: Strait, Christopher, Nayak, Aditya, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: Lidar has the ability to supplant or compliment many current measurement technologies in ocean optics. Lidar measures Inherent Optical Properties over long distances without impacting the orientation and assemblages of particles it measures, unlike many systems today which require pumps and flow cells. As an active sensing technology, it has the benefit of being independent of time of day and weather. Techniques to interpret oceanographic lidar lags behind atmospheric lidar inversion...
Show moreLidar has the ability to supplant or compliment many current measurement technologies in ocean optics. Lidar measures Inherent Optical Properties over long distances without impacting the orientation and assemblages of particles it measures, unlike many systems today which require pumps and flow cells. As an active sensing technology, it has the benefit of being independent of time of day and weather. Techniques to interpret oceanographic lidar lags behind atmospheric lidar inversion techniques to measure optical properties due to the complexity and variability of the ocean. Unlike in the atmosphere, two unknowns in the lidar equation backscattering at 180o (𝛽𝜋) and attenuation (c) do not necessarily covary. A lidar system developed at the Harbor Branch Oceanographic Institute is used as a test bed to validate a Monte-Carlo model to investigate the inversion of optical properties from lidar signals. Controlled tank experiments and field measurements are used to generate lidar waveforms and provide optical situations to model. The Metron EODES backscatter model is used to model waveforms. A chlorophyll based forward optical model provides a set of 1500 unique optical situations which are modeled to test inversion techniques and lidar geometries. Due to issues with the lidar system and model the goal of validating the model as well as a more mature inversion experiment were not completed. However, the results are valuable to show the complexity and promise of lidar systems.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013631
Subject Headings: Lidar, Remote sensing, Seawater--Optical properties
Format: Document (PDF)

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