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Title: Empirical Analysis of the Dissipated Acoustic Energy in Wave Breaking.
Creator: Francke, Kristina, Dhanak, Manhar, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: In this research an attempt is made at explaining the physical processes behind energy dissipation during wave breaking, through spectral analysis of the resulting sound. The size of an air bubble can be directly linked to the frequency of the sound that is heard using the simple harmonic solution to the Rayleigh–Plesset equation. It indicates the inverse relationship between frequency and bubble size. And this relationship has been used to identify wave breaking in general [MANASSEH 2006]....
Show moreIn this research an attempt is made at explaining the physical processes behind energy dissipation during wave breaking, through spectral analysis of the resulting sound. The size of an air bubble can be directly linked to the frequency of the sound that is heard using the simple harmonic solution to the Rayleigh–Plesset equation. It indicates the inverse relationship between frequency and bubble size. And this relationship has been used to identify wave breaking in general [MANASSEH 2006]. Now this research goes a step farther and looks at how the frequency spectrum of the sound changes with time, in an effort to understand the general pattern and from that to deduce an empirical equation that describes the breaking down of turbulence during a wave breaking event. Two main processes have been identified, with the second process having three main indicators that are necessary to evidence wave breaking. The first process is a near instantaneous shattering of the initial air bubble into much smaller metastable bubbles of a size that appears to be common for all waves independent of wave height. Then in the second process, the bubbles continue to break down following a recognisable pattern.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013504
Subject Headings: Waves, Energy dissipation, Spectral analysis, Fluid dynamics, Acoustic energy
Format: Document (PDF)

Title: SYNTHETIC FIBER REINFORCED CONCRETE PERFORMANCE AFTER PROLONGED ENVIRONMENTAL EXPOSURE UTILIZING THE MODIFIED INDIRECT TENSILE TEST.
Creator: Ellis, Spencer G., Presuel-Moreno, Francisco, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: In order to study the mechanical performance of dry-cast synthetic fiber reinforced concrete (SynFRC), samples of varying geometry, fiber content, and environmental exposure were developed and tested using the modified indirect tensile test. The samples created consisted of three different thicknesses (with two different geometries), and six different fiber contents that differed in either type, or quantity, of fibers. Throughout the duration of this research, procedures for inflicting...
Show moreIn order to study the mechanical performance of dry-cast synthetic fiber reinforced concrete (SynFRC), samples of varying geometry, fiber content, and environmental exposure were developed and tested using the modified indirect tensile test. The samples created consisted of three different thicknesses (with two different geometries), and six different fiber contents that differed in either type, or quantity, of fibers. Throughout the duration of this research, procedures for inflicting detrimental materials into the concrete samples were employed at a number of different environments by implementing accelerated rates of deterioration using geometric adjustments, increased temperature exposure, wetting/drying cycles, and preparation techniques. The SynFRC samples studied were immersed in a wide range of environments including: the exposure of samples to high humidity and calcium hydroxide environments, which served at the control group, while the sea water, low pH, and barge conditioning environments were used to depict the real world environments similar to what would be experienced in the Florida ecosystem. As a result of this conditioning regime, the concrete was able to imitate the real-world effects that the environments would have inflicted if exposed for long durations after an exposure period of only 20-24 months. Having adequately conditioned the samples in their respective environments, they were then tested (and forensically investigated) using the modified indirect tensile testing method to gather data regarding each sample’s toughness and load handling capability. By analyzing the results from each sample, the toughness was calculated by taking the area under the force displacement curve. From these toughness readings it was found that possible degradation occurred between the fiber-matrix interface of some of the concrete samples conditioned in the Barge environment. From these specimens that were immersed in the barge environment, a handful of them exhibited multiple episodes of strain softening characteristics within their force displacement curves. In regard to the fibers used within the samples, the PVA fibers tended to pull off more while the Tuff Strand SF fibers had the highest tendency to break (despite some of the fibers showing similar pull off and breaking failure characteristics). When it comes to the overall thickness of the sample, there was clear correlation between the increase in size and the increase in sample toughness, however the degree to which it correlates varies from sample to sample.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013466
Subject Headings: Reinforced concrete, Fiber-reinforced concrete--Testing, Reinforced concrete--Mechanical properties, Tensile Strength, Concrete—Environmental testing
Format: Document (PDF)

Title: SUSTAINING CHAOS USING DEEP REINFORCEMENT LEARNING.
Creator: Vashishtha, Sumit, Verma, Siddhartha, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: Numerous examples arise in fields ranging from mechanics to biology where disappearance of Chaos can be detrimental. Preventing such transient nature of chaos has been proven to be quite challenging. The utility of Reinforcement Learning (RL), which is a specific class of machine learning techniques, in discovering effective control mechanisms in this regard is shown. The autonomous control algorithm is able to prevent the disappearance of chaos in the Lorenz system exhibiting meta-stable...
Show moreNumerous examples arise in fields ranging from mechanics to biology where disappearance of Chaos can be detrimental. Preventing such transient nature of chaos has been proven to be quite challenging. The utility of Reinforcement Learning (RL), which is a specific class of machine learning techniques, in discovering effective control mechanisms in this regard is shown. The autonomous control algorithm is able to prevent the disappearance of chaos in the Lorenz system exhibiting meta-stable chaos, without requiring any a-priori knowledge about the underlying dynamics. The autonomous decisions taken by the RL algorithm are analyzed to understand how the system’s dynamics are impacted. Learning from this analysis, a simple control-law capable of restoring chaotic behavior is formulated. The reverse-engineering approach adopted in this work underlines the immense potential of the techniques used here to discover effective control strategies in complex dynamical systems. The autonomous nature of the learning algorithm makes it applicable to a diverse variety of non-linear systems, and highlights the potential of RLenabled control for regulating other transient-chaos like catastrophic events.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013498
Subject Headings: Machine learning--Technique, Reinforcement learning, Algorithms, Chaotic behavior in systems, Nonlinear systems
Format: Document (PDF)

Title: NOISE PREDICTION METHODS.
Creator: Perry, Nicole Kent, Glegg, Stewart, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: Noise prediction methods are necessary in aspects of aerodynamic and hydrodynamic engineering. Predictive models of noise from rotating machinery ingesting turbulence is of much interest and relatively recently studied. This thesis presents a numerical method processed in a series of three codes that was written and edited to receive input for geometrical features of rotating machinery, as well as, adjustments to turbulent operating conditions. One objective of this thesis was to create a...
Show moreNoise prediction methods are necessary in aspects of aerodynamic and hydrodynamic engineering. Predictive models of noise from rotating machinery ingesting turbulence is of much interest and relatively recently studied. This thesis presents a numerical method processed in a series of three codes that was written and edited to receive input for geometrical features of rotating machinery, as well as, adjustments to turbulent operating conditions. One objective of this thesis was to create a platform of analysis for any rotor design to obtain five parameters necessary for noise prediction; 1) the hydrodynamic inflow angle to each blade section, 2) chord length as a function of radius, 3) the cylindrical radius of each blade section, 4) & 5) the leading edge as a function of span in both the rotor-plane and as a function of axial distance downstream. Another objective of this thesis was to use computational fluid dynamics (CFD), specifically by using a Reynold’s-Averaged Navier-Stokes (RANS) Shear Stress Transport (SST) 𝑘 − 𝜔 model simulation in ANSYS Fluent, to obtain the turbulent kinetic energy distribution, also necessary in the noise prediction method presented. The purpose of collecting the rotor geometry data and turbulent kinetic energy data was to input the values into the first of the series of codes and run the calculation so that the output spectra could be compared to experimental noise measurements conducted at the Stability Wind Tunnel at Virginia Tech. The comparison shows that the prediction method results in data that can be reliable if careful attention is payed to the input parameters and the length scale used for analysis. The significance of this research is the noise prediction method presented and used simplifies the model of turbulence by using a correlation function that can be determined by a one-dimensional function while also simplifying the iterations completed on rotor blade to calculate the unsteady forces.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013487
Subject Headings: Noise, Aerodynamic noise, Hydrodynamics, Noise control--Mathematical models
Format: Document (PDF)

Title: On the Drainage Vortices of Liquid in a Container with Two Outlets.
Creator: Stankovic, Radivoje, Su, Tsung-Chow, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: When a liquid drains through a hole in a container, a vortex may form between the surface and the drainage hole. An interesting phenomenon occurs in the presence of two drainage holes. Only one vortex forms, while the other hole will mostly drain as sink flow. In addition, the vortex can switch between one hole and the other with regular periodicity. The primary goal of this study is to measure this periodicity under varying conditions (height of water in the container, diameter of the...
Show moreWhen a liquid drains through a hole in a container, a vortex may form between the surface and the drainage hole. An interesting phenomenon occurs in the presence of two drainage holes. Only one vortex forms, while the other hole will mostly drain as sink flow. In addition, the vortex can switch between one hole and the other with regular periodicity. The primary goal of this study is to measure this periodicity under varying conditions (height of water in the container, diameter of the drainage holes, and distance between drainage holes). Additionally, a study concerning the volume flow rates of vortical vs. sink flow out of the drainage holes was conducted. In the case of two drainage holes, when the height of the water was decreased in the container, the diameter of drainage holes decreased, or the distance between drainage holes was increased, the switching period was shown to decrease.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013572
Subject Headings: Drainage, Vortex-motion
Format: Document (PDF)

Title: Development of MnO2 Hollow Nanoparticles for Drug Delivery.
Creator: Greene, Allison, Kang, Yunqing, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: This thesis reports the development of a novel drug delivery system consisting of hollow nanoparticles, formed from manganese dioxide (δ-MnO2) sheets, that are coated with polydopamine and folic acid to selectively target cancer cells. The biodegradability and colloidal stability of the uncoated hollow nanoparticles were investigated in comparison to solid MnO2 nanoparticles and graphene oxide sheets. The MnO2 hollow nanoparticles degraded at a faster rate and seem to have a higher surface...
Show moreThis thesis reports the development of a novel drug delivery system consisting of hollow nanoparticles, formed from manganese dioxide (δ-MnO2) sheets, that are coated with polydopamine and folic acid to selectively target cancer cells. The biodegradability and colloidal stability of the uncoated hollow nanoparticles were investigated in comparison to solid MnO2 nanoparticles and graphene oxide sheets. The MnO2 hollow nanoparticles degraded at a faster rate and seem to have a higher surface area and better colloidal dispersion than solid MnO2 nanoparticles. Xanthan gum was proven to improve colloidal dispersion of these hollow nanoparticles and were used for further cell studies. In this study, cancer and healthy cells were treated with coated hollow nanoparticles, and results indicate that this novel hollow nanoparticle may preferentially target and kill cancer cells. Particle aggregation has shown to be toxic to cells. Further studies with this novel drug delivery system may lead to a groundbreaking solution to targeted cancer therapy.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013513
Subject Headings: Drug Delivery Systems, Nanoparticles, Manganese dioxide, Xanthan gum, Cancer cells
Format: Document (PDF)

Title: The Effect of Shear Sheltering on Trailing Edge Noise: A Theoretical Study.
Creator: Jimenez, Ignacio, Glegg, Stewart, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: Shear sheltering is defined as the effect of the mean flow velocity profile in a boundary layer on the turbulence caused by an imposed gust. In aeroacoustic applications turbulent boundary layers interacting with blade trailing edges or roughness elements are an important source of sound, and the effect of shear sheltering on these noise sources has not been studied in detail. Since the surface pressure spectrum below the boundary layer is the primary driver of trailing edge and roughness...
Show moreShear sheltering is defined as the effect of the mean flow velocity profile in a boundary layer on the turbulence caused by an imposed gust. In aeroacoustic applications turbulent boundary layers interacting with blade trailing edges or roughness elements are an important source of sound, and the effect of shear sheltering on these noise sources has not been studied in detail. Since the surface pressure spectrum below the boundary layer is the primary driver of trailing edge and roughness noise, this thesis considers the effect that shear sheltering has on the surface pressure spectrum below a boundary layer. This study presents a model of the incoming turbulence as a vortex sheet at a specified height above the surface and shows, using canonical boundary layers and approximations to numerical results, how the mean flow velocity profile can be manipulated to alter the surface pressure spectrum and hence the associated trailing edge noise. The results from this model demonstrate that different mean velocity profiles drive significant changes in the unsteady characteristics of the flow. The surface pressure fluctuations results also suggest that boundary layers where the shear in the mean velocity profile is significant can be beneficial for the reduction of trailing edge noise at particular frequencies.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013535
Subject Headings: Turbulent boundary layer, Trailing edges (Aerodynamics), Aeroacoustics, Boundary layer noise, Shear sheltering
Format: Document (PDF)

Title: SORPTIVITY, RESISTIVITY AND POROSITY OF CONCRETE CONTAINING SUPPLEMENTARY CEMENTITIOUS MATERIALS.
Creator: Barman, Sanjoy, Presuel-Moreno, Francisco, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: Supplementary cementitious materials (SCMs), are beneficial when used as partial replacement of cement in concrete mixtures for coastal concrete structures, blended with Portland cement (binary or ternary mixes), i.e., high-performance concrete provides improved properties when exposed to marine harsh environment. In order to characterize selected durability properties of different concrete mixtures, a testing program was established. The intent of this study consists of testing 10cm diameter...
Show moreSupplementary cementitious materials (SCMs), are beneficial when used as partial replacement of cement in concrete mixtures for coastal concrete structures, blended with Portland cement (binary or ternary mixes), i.e., high-performance concrete provides improved properties when exposed to marine harsh environment. In order to characterize selected durability properties of different concrete mixtures, a testing program was established. The intent of this study consists of testing 10cm diameter x 20cm long concrete specimens prepared with a range of different mix designs. 1) to evaluate the rate of water absorption due to capillary suction, referred to as sorptivity, 2) to evaluate the concrete surface resistivity, 3) to evaluate and compare the total porosity of specimens with different mixes, and 4) to obtain correlations between resistivity and sorptivity. All of these experimental tests were carried out according to ASTM International Standards (Sorptivity, Porosity) and Florida Method of Test (Resistivity). The tests were performed on concrete samples at various ages. Moreover, The results provided a fast and reasonable approximation of the concrete durability over time. Ordinary portland cement was partially replaced with supplementary cementitious materials including: fly ash (20%), silica fume (8%) and blast furnace slag (50%). These SCMs are highly effective in creating more durable concrete design mixtures. The water-to-cementitious (w/cm) ratios of 0.41 and 0.35 were investigated. The concrete that contains pozzolanic materials has demonstrated progress in extending the time for initiation of corrosion. The test results obtained indicate that the concurrent inclusion of fly ash and silica fume greatly reduced water penetration. The mixes containing slag also showed lower porosity and water absorption result, when compared to specimens containing fly ash only. Ternary concrete mixtures specimens showed much higher surface resistivity values than binary mixture specimens. These results suggest that reducing w/cm ratio, adding SCMs to concrete mixtures improved the concrete durability. The possibilities for the risks of corrosion initiation would be minimized (delayed) by prescriptive and then performance-based concrete blends with SCM materials optimized for service exposure in aggressive environments.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013633
Subject Headings: Fly ash, High performance concrete, Porosity, Silica fume, Slag
Format: Document (PDF)

Title: LOCALIZED FLOW MODIFICATION TO INCREASE POWER CAPTURE OF A SMALL-SCALE FLOATING UNDERSHOT WATERWHEEL.
Creator: Hess, Sullivan, Dhanak, Manhar, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: The goal of the work described in this thesis is to design a flow augmentation device to increase the power capture and efficiency of a small-scale floating Under-Shot Water Wheel (USWW) currently being developed by Florida Atlantic University research funded by the U.S Department of Energy. The flow concentrator subsystem is intended to maximize the kinetic energy extracted by the marine hydrokinetic (MHK) energy collection device through modification of the local flow field across the...
Show moreThe goal of the work described in this thesis is to design a flow augmentation device to increase the power capture and efficiency of a small-scale floating Under-Shot Water Wheel (USWW) currently being developed by Florida Atlantic University research funded by the U.S Department of Energy. The flow concentrator subsystem is intended to maximize the kinetic energy extracted by the marine hydrokinetic (MHK) energy collection device through modification of the local flow field across the capture plane. The primary objective is to increase the velocity and/or rate of mass inflow through the turbine through inserting a streamlined body in the region of interest. By utilizing the resulting flow field to increase hydraulic forcing on the waterwheel blades, the torque and/or RPM of the USWW can be increased. Based on experimental testing in the FAU wave tank at 1:5 prototype scale (280 mm wheel diameter) the flow concentrator was shown to produce an increase in device power coefficient of 17-55% measured over a velocity range of 0.16-0.45 m/s.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013613
Subject Headings: Water-wheels, Renewable energy
Format: Document (PDF)

Title: APPLYING BLIND SOURCE SEPARATION TO MAGNETIC ANOMALY DETECTION.
Creator: Nieves, Eric, Beaujean, Pierre-Philippe, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: The research shows a novel approach for the Magnetic Anomaly Differentiation and Localization Algorithm, which simultaneously localizes multiple magnetic anomalies with weak total field signatures (tens of nT). In particular, it focuses on the case where there are two homogeneous targets with known magnetic moments. This was done by analyzing the magnetic signals and adapting Independent Component Analysis (ICA) and Simulated Annealing (SA) to solve the problem statement. The results show the...
Show moreThe research shows a novel approach for the Magnetic Anomaly Differentiation and Localization Algorithm, which simultaneously localizes multiple magnetic anomalies with weak total field signatures (tens of nT). In particular, it focuses on the case where there are two homogeneous targets with known magnetic moments. This was done by analyzing the magnetic signals and adapting Independent Component Analysis (ICA) and Simulated Annealing (SA) to solve the problem statement. The results show the groundwork for using a combination of fastICA and SA to give localization errors of 3 meters or less per target in simulation and achieved a 58% success rate. Experimental results experienced additional errors due to the effects of magnetic background, unknown magnetic moments, and navigation error. While one target was localized within 3 meters, only the latest experimental run showed the second target approaching the localization specification. This highlighted the need for higher signal-to-noise ratio and equipment with better navigational accuracy. The data analysis was used to provide recommendations on the needed equipment to minimize observed errors and improve algorithm success.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013610
Subject Headings: Magnetic anomalies, Simulated annealing (Mathematics), Independent component analysis, Unmanned vehicles
Format: Document (PDF)

Title: STATISTICAL MODELING OF SHIP AIRWAKES INCLUDING THE FEASIBILITY OF APPLYING MACHINE LEARNING.
Creator: Krishnan, Vaishakh, Gaonkar, Gopal, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: Airwakes are shed behind the ship’s superstructure and represent a highly turbulent and rapidly distorting flow field. This flow field severely affects pilot’s workload and such helicopter shipboard operations. It requires both the one-point statistics of autospectrum and the two-point statistics of coherence (normalized cross-spectrum) for a relatively complete description. Recent advances primarily refer to generating databases of flow velocity points through experimental and computational...
Show moreAirwakes are shed behind the ship’s superstructure and represent a highly turbulent and rapidly distorting flow field. This flow field severely affects pilot’s workload and such helicopter shipboard operations. It requires both the one-point statistics of autospectrum and the two-point statistics of coherence (normalized cross-spectrum) for a relatively complete description. Recent advances primarily refer to generating databases of flow velocity points through experimental and computational fluid dynamics (CFD) investigations, numerically computing autospectra along with a few cases of cross-spectra and coherences, and developing a framework for extracting interpretive models of autospectra in closed form from a database along with an application of this framework to study the downwash effects. By comparison, relatively little is known about coherences. In fact, even the basic expressions of cross-spectra and coherences for three components of homogeneous isotropic turbulence (HIT) vary from one study to the other, and the related literature is scattered and piecemeal. Accordingly, this dissertation begins with a unified account of all the cross-spectra and coherences of HIT from first principles. Then, it presents a framework for constructing interpretive coherence models of airwake from a database on the basis of perturbation theory. For each velocity component, the coherence is represented by a separate perturbation series in which the basis function or the first term on the right-hand side of the series is represented by the corresponding coherence for HIT. The perturbation series coefficients are evaluated by satisfying the theoretical constraints and fitting a curve in a least squares sense on a set of numerically generated coherence points from a database. Although not tested against a specific database, the framework has a mathematical basis. Moreover, for assumed values of perturbation series constants, coherence results are presented to demonstrate how coherences of airwakes and such flow fields compare to those of HIT.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013629
Subject Headings: Ships--Aerodynamics, Turbulence--Statistical methods, Machine learning
Format: Document (PDF)

Title: Hydrodynamic Interactions of Pitching Hydrofoils in Close Formation.
Creator: Boltri, Michael A., Curet, Oscar M., Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: Hydrodynamics interaction is a factor in the performance of fish schooling or underwater vessels in close formation. In this work, we visualized the wake structure of pitching hydrofoils using an inclined soap film. We considered one-, two-, three- and nine-foil configurations with different spacing and actuation parameters: amplitude (A), frequency (f), phase difference (), and flow speed (U). The wake structures were recorded with a high-speed camera and analyzed to measure the vortex...
Show moreHydrodynamics interaction is a factor in the performance of fish schooling or underwater vessels in close formation. In this work, we visualized the wake structure of pitching hydrofoils using an inclined soap film. We considered one-, two-, three- and nine-foil configurations with different spacing and actuation parameters: amplitude (A), frequency (f), phase difference (), and flow speed (U). The wake structures were recorded with a high-speed camera and analyzed to measure the vortex angle created. The wake structure of two- and three-foil configurations were compared with the Strouhal number, St = fA/U, of a single foil. For the nine-foil configuration, the wake velocity and the standard deviation of the velocity were used to interpret the hydrodynamic interaction. It was found that both spacing and phase difference between foils are relevant in the hydrodynamic interaction. Qualitative observations are also made, and vortex street behavior characteristics are identified.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013627
Subject Headings: Hydrodynamics, Hydrofoils
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)

Title: Corrosion Propagation of Reinforcing Steel Embedded in Binary and Ternary Concrete.
Creator: Hoque, Kazi Naimul, Presuel-Moreno, Francisco, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: The Florida Department of Transportation (FDOT) has been using supplementary cementitious materials while constructing steel reinforced concrete marine bridge structures for over three decades. It has been found from previous studies that such additions in concrete mix makes the concrete more durable. This research was conducted to better understand the corrosion propagation stage of steel rebar embedded in high performance concrete exposed to high humidity environment. Reinforced concrete...
Show moreThe Florida Department of Transportation (FDOT) has been using supplementary cementitious materials while constructing steel reinforced concrete marine bridge structures for over three decades. It has been found from previous studies that such additions in concrete mix makes the concrete more durable. This research was conducted to better understand the corrosion propagation stage of steel rebar embedded in high performance concrete exposed to high humidity environment. Reinforced concrete samples that were made with binary mixes, and ternary mixes were considered. None of these concretes had any admixed chloride to start with. An accelerated chloride transport method was used to drive chloride ions into the concrete so that chlorides reached and exceed the chloride threshold at the rebar surface and hence the corrosion process initiated after a short period of time (within few days to few months). Once corrosion has initiated the corrosion propagation can be studied. Electrochemical measurements such as rebar potential measurements, Linear Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy (EIS), and Galvanostatic Pulse (GP) measurements were taken at regular intervals (during and after the electro-migration process) to observe the corrosion propagation in each sample. During the propagation stage, reinforcement eventually reached negative potentials values (i.e., Ecorr≤ –0.200 Vsce) for all the samples. The corrected polarization resistance (Rc) was calculated by subtracting the concrete solution resistance from the apparent polarization resistance measured. The Rc values obtained from LPR and GP measurements were converted to corrosion current (as the corroding area is unknown), and these corrosion current values measured over time were used to obtain the calculated mass loss (using Faraday’s Law). A comparison was made of the calculated corrosion current obtained using the LPR and GP tests. A comparison of mass loss was also obtained from the values measured from LPR and GP tests. From the experimental results, it was observed that the corrosion current values were largely dependent on the length of solution reservoirs. For specimens cast with single rebar as well as three rebars, the most recent corrosion current values (measurements taken between July 2018 to October 2020) in general were larger for the rebars that are embedded in specimens prepared with SL mix, followed by specimens prepared with FA, T1, and T2 mixes respectively. The range of corrosion current values (most recent) were 0.8-33.8 μA for SL samples, 0.5-22.5 μA for FA samples, 0.8-14.8 μA for T1 samples, and 0.7-10.4 μA for T2 samples respectively. It was also found that the calculated mass loss values were larger for rebars that are embedded in specimens (single rebar and three rebars) prepared with SL mix, followed by specimens prepared with FA, T1, and T2 mixes respectively. The range of calculated mass loss values were 0.07-1.13 grams for SL samples, 0.06-0.62 grams for FA samples, 0.12-0.54 grams for T1 samples, and 0.06-0.40 grams for T2 samples respectively. A variety of corrosion related parameters (Ecorr, Rs, Rc, and Icorr) and calculated theoretical mass loss values observed, were due to the changing parameters such as concrete compositions, concrete cover thickness, rebar diameter, total ampere-hour applied, and reservoir size. The specimens showed no visual signs of corrosion such as cracks or corrosion products that reached the concrete surface. The actual size of the corroding sites was unknown as the specimens were not terminated for forensic analysis. The size of the corroding sites could affect how much corrosion products are required to crack the concrete. It is speculated that the corrosion products in liquid form penetrated the pore structure but did not build up enough to cause cracks. No cracks or corrosion bleed outs were observed within the monitored propagation period of approximately 1600 days.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013634
Subject Headings: Concrete, Concrete bridges--Corrosion, Carbon steel
Format: Document (PDF)

Title: MECHANICAL FATIGUE TESTING OF HUMAN RED BLOOD CELLS USING THE ELECTRO-DEFORMATION METHOD.
Creator: Qiang, Yuhao, Du, Sarah, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Human red blood cells (RBCs) must undergo severe deformation to pass through narrow capillaries and submicronic splenic slits for several hundred thousand times in their normal lifespan. Studies of RBC biomechanics have been mainly focused on cell deformability measured from a single application of stress using classical biomechanical techniques, such as optical tweezers and micropipette aspiration. Mechanical fatigue effect on RBCs under cyclic loadings of stress that contributes to the...
Show moreHuman red blood cells (RBCs) must undergo severe deformation to pass through narrow capillaries and submicronic splenic slits for several hundred thousand times in their normal lifespan. Studies of RBC biomechanics have been mainly focused on cell deformability measured from a single application of stress using classical biomechanical techniques, such as optical tweezers and micropipette aspiration. Mechanical fatigue effect on RBCs under cyclic loadings of stress that contributes to the membrane failure in blood circulation is not fully understood. This research developed a new experimental method for mechanical fatigue testing of RBCs using amplitude-modulated electro-deformation technique. Biomechanical parameters of individually tracked RBCs show strong correlations with the number of the loading cycles. Effects of loading configurations on the cellular fatigue behavior of RBCs is further studied. The results uniquely establish the important role of mechanical fatigue in influencing physical properties of biological cells. They further provide insights into the accumulated membrane damage during blood circulation, paving the way for further investigations of the eventual failure of RBCs in various hemolytic pathologies.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013340
Subject Headings: Red blood cells, Erythrocytes--Deformability, Biomechanics--Research--Methodology
Format: Document (PDF)

Title: INITIATION AND PROPAGATION OF CORROSION IN DRY-CAST REINFORCED CONCRETE PIPES WITH ENVIRONMENTAL EFFECTS.
Creator: Balasubramanian, Hariharan, Presuel-Moreno, Francisco, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This research was conducted to better understand the corrosion propagation stage on dry-cast reinforced concrete pipes (DCRCPs) while exposed to high moisture conditions and chlorides. Corrosion initiation and propagation were studied in instrumented specimens obtained from segments of dry-cast reinforced concrete pipes. All specimens were subjected to accelerated chloride transport by the application of an electric field. Corrosion of the steel wire mesh initiated after a few days to a few...
Show moreThis research was conducted to better understand the corrosion propagation stage on dry-cast reinforced concrete pipes (DCRCPs) while exposed to high moisture conditions and chlorides. Corrosion initiation and propagation were studied in instrumented specimens obtained from segments of dry-cast reinforced concrete pipes. All specimens were subjected to accelerated chloride transport by the application of an electric field. Corrosion of the steel wire mesh initiated after a few days to a few months rather than several years. The specimens were then transferred to high moisture environments (immersed in water, high humidity and/or covered with wet sand) during the corrosion propagation stage. Reinforcement potentials, linear polarization resistance (LPR) and Electrochemical Impedance Spectroscopy (EIS) measurements were carried out periodically. During the propagation stage in different exposures, reinforcement eventually reached negative potentials values (< –-0.55 Vsce), which suggest mass transfer limitations. These specimens showed no visual signs of corrosion such as cracks or corrosion products except the ones exposed to high humidity and laboratory environments; where some corrosion products have reached the concrete surface. Moreover, the apparent corrosion rate values obtained suggest high corrosion rates. No crack appearance on specimens exposed to other conditions could be explained by the porosity of the specimens; the corrosion products moved into saturated pores. It is speculated that although there might be mass transfer limitations present, the current demanded by the anode is being balanced by a larger cathode area due to macrocell effects since the high moisture conditions likely reduced the concrete resistivity and increased the throwing power. The corrected polarization resistance (Rc) was calculated by subtracting the solution resistance from the apparent polarization resistance measured. The Rc values measured over time were used to obtain the calculated mass loss (using Faraday’s Law). Most specimens were forensically analyzed and the measured mass loss compared to the calculated mass loss. The forensic examination includes the measurement of the actual corroding areas. The measured corroding areas were used to obtain corrosion current density (icorr) values. A comparison was made of the calculated corrosion current densities obtained using the linear polarization resistance method (LPR) and the extrapolation method from cyclic polarization tests. It was evident that most of the specimens’ corrosion rates were significantly high. The corrosion products filled the wet-pores inside the concrete and provide an explanation for no cracks or corrosion bleed outs being visually observed on the specimens.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013182
Subject Headings: Reinforced concrete, Corrosion, Environmental effects
Format: Document (PDF)

Title: Modified Indirect Tension Testing of Synthetic Fiber Reinforced Concrete Samples Exposed to Different Environmental Conditions.
Creator: Santillan Barragan, Ingrid Susana, Presuel-Moreno, Francisco, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Laboratory experiments were conducted to observe, document and evaluate the mechanical behavior of Fiber Reinforced Concrete after being submitted to five different environments for 8 months. The specimens were molded and reinforced with synthetic fibers with a composition similar to that used for dry-cast concrete. Four different types of fibers with different composition were used. The fibers were mixed with the concrete to create the samples and the samples were exposed to different...
Show moreLaboratory experiments were conducted to observe, document and evaluate the mechanical behavior of Fiber Reinforced Concrete after being submitted to five different environments for 8 months. The specimens were molded and reinforced with synthetic fibers with a composition similar to that used for dry-cast concrete. Four different types of fibers with different composition were used. The fibers were mixed with the concrete to create the samples and the samples were exposed to different environmental conditions. Some of these environments were meant to increase degradation of the interface fiber-concrete to simulate longevity and imitate harsh environments or marine conditions. The environments consisted of: a high humidity locker (laboratory conditions), submerged in the Intracoastal Waterway in a barge (SeaTech), a wet/dry cycle in seawater immersion simulating a splash/tidal zone, low pH wet/dry seawater immersion cycle and samples submerged in calcium hydroxide solution. The latter three were in an elevated temperature tank (87-95°F) to increase degradation process. The specimens were monitored weekly and the environments were controlled. Then, specimens were evaluated using different mechanical testing as the Indirect Tensile (IDT) test method, compressive strength according to ASTM standards. Results of testing were documented and observed in this study for further understanding of mechanical properties of Fiber Reinforced concrete. Forensic observation of fiber distribution after the IDT tests were also performed.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013258
Subject Headings: Concrete--Environmental testing, Fiber-reinforced concrete--Testing, Tensile Strength, Materials--Compression testing
Format: Document (PDF)

Title: Modeling and Experimental Study of Evaporation and Diffusion of Water Droplets on Foam Substrates.
Creator: Tian, Yining, Du, Sarah E., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The objective of this thesis is to develop a new experimental method to characterize the diffusion of water in polymer resins, based on the evolution in the volume of water droplets as a function of time. A finite element model is established to model the mass transport of water droplet through evaporation and diffusion processes. Diffusivity of water into polymer resins is then extracted by matching the volume variation of the simulated water droplet to the experimental results. Capability...
Show moreThe objective of this thesis is to develop a new experimental method to characterize the diffusion of water in polymer resins, based on the evolution in the volume of water droplets as a function of time. A finite element model is established to model the mass transport of water droplet through evaporation and diffusion processes. Diffusivity of water into polymer resins is then extracted by matching the volume variation of the simulated water droplet to the experimental results. Capability of this method is demonstrated by determining the diffusivity of water into void-free epoxy and epoxy samples with voids. Diffusion coefficient value obtained from this method agrees with data from conventional water immersion method. The significantly small scale of the water droplet (less than 10 microliter) allows rapid characterization of diffusivity in hours instead of months as typically required by the conventional immersion method. The method developed here provides a useful tool for rapid and effective characterization of diffusivity of water in polymer substrates and can be extended to other substances as well.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013270
Subject Headings: Polymers, Resins, Diffusion, Water, Evaporation--Experiments
Format: Document (PDF)

Title: Microbial Induced Degradation in Synthetic Fiber Reinforced Concrete Samples in South Florida.
Creator: Parkinson, Jacqueline Cecile, Presuel-Moreno, Francisco, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Synthetic fiber reinforced concrete sample sets were exposed to two different environments. One set, of six samples, was exposed to filtered seawater in the lab with wet and dry cycles, while the other set of samples was exposed, on a barge, to the marine environment, in the intracoastal waterways, at SeaTech. The samples were exposed for 8 months, and then removed for experimental and mechanical testing. Upon removal, the barge samples were photographed to observe surface organisms that were...
Show moreSynthetic fiber reinforced concrete sample sets were exposed to two different environments. One set, of six samples, was exposed to filtered seawater in the lab with wet and dry cycles, while the other set of samples was exposed, on a barge, to the marine environment, in the intracoastal waterways, at SeaTech. The samples were exposed for 8 months, and then removed for experimental and mechanical testing. Upon removal, the barge samples were photographed to observe surface organisms that were attached to each sample. The barge samples, after cleaning, were then exposed to UV light to observe surface bacteria. The barge samples were also taken to Harbor Branch facility for DNA testing, and then sent in for sequencing. This sequencing was used to identify the organisms that were present inside the concrete samples. An Indirect Tensile Strength Test, IDT, was performed on both sets of samples to observe the first crack, max load, and fracture toughness of each sample. The Barge samples had a lower first crack, max load, and fracture toughness, which means that it took less force to break these samples, than the Seawater samples. As the fiber content increased, the Seawater samples grew stronger, while the Barge samples grew weaker. Also, as the fiber content increased, the biodiversity found on the surface of the Barge samples increased as well.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013251
Subject Headings: Fiber-reinforced concrete, Florida, Concrete--Deterioration, Microbes
Format: Document (PDF)

Title: POST PROCESSING METHODS FOR THREE DIMENSIONAL IMAGING LIDAR WITH MULTI-SCALE CHARACTERIZATION OF SUBSEA ORGANISMS.
Creator: McKenzie, Trevor Lee, Nayak, Aditya, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: The thesis objective is to develop protocols that provide analysis and interpretation for data from a pulsed laser serial scanning lidar system for underwater imaging. The specific focus is remotely observing marine organisms in the centimeter size range in the poorly understood mesopelagic realm of the ocean. The Unobtrusive Multi-Static Lidar Imager (UMSLI) system captures an expansive volume scan field with differentiating imaging resolution per planar slice, allowing precise assignment of...
Show moreThe thesis objective is to develop protocols that provide analysis and interpretation for data from a pulsed laser serial scanning lidar system for underwater imaging. The specific focus is remotely observing marine organisms in the centimeter size range in the poorly understood mesopelagic realm of the ocean. The Unobtrusive Multi-Static Lidar Imager (UMSLI) system captures an expansive volume scan field with differentiating imaging resolution per planar slice, allowing precise assignment of location for organisms in the field of view. The multi-static highly collimated beams are recorded by a photo-multiplier tube receiver as a time lapse waveform of the returned energy flux, each waveform comprehensibly represents an image pixel in spatially and temporally. Complied lidar waveforms produce an array of returns which signify the magnitude of backscatter from varying sized particles across the observed volume. These volume scans are uniquely evaluated and transformed for each time bin through a processing method which extracts particle characteristics and statistics based on adaptive spatial and temporal techniques. The post processing method aims to greatly extend the capabilities of the lidar imaging system to extract particles. Results of the processing method are presented as particle counts and particle size distributions of the water columns during observed vertical migration periods. Methods are compared with other optical devices for validation, and results are interpreted to better understand the organism distribution in the mesopelagic and their behavior, with respect to diel vertical migrations.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013396
Subject Headings: Underwater imaging systems, Three-dimensional imaging--Methodology, Optical radar, Vertical distribution (Aquatic biology)
Format: Document (PDF)

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