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- Title
- Theoretical analysis of reinforced and prestressed concrete bridge members strengthened with CFRP laminates.
- Creator
- Qu, Rong., Florida Atlantic University, Arockiasamy, Madasamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Nonlinear finite element analyses of the reinforced rectangular beams, prestressed solid slab and prestressed voided slab retrofitted with CFRP laminates are carried out using the software ANSYS(version 5.0) on the Sunwork station. The computer analyses are based on the proposed stress-strain relationship considering the effects of tensile stress on both elastic modulus and maximum compressive stress of concrete. Several assumptions are made in predicting the loss of tensile strength due to...
Show moreNonlinear finite element analyses of the reinforced rectangular beams, prestressed solid slab and prestressed voided slab retrofitted with CFRP laminates are carried out using the software ANSYS(version 5.0) on the Sunwork station. The computer analyses are based on the proposed stress-strain relationship considering the effects of tensile stress on both elastic modulus and maximum compressive stress of concrete. Several assumptions are made in predicting the loss of tensile strength due to crack, confinement due to the laminate bonding, tensile strength due to the prestress force, failure pattern due to the concentrated stress adjacent to the loading point and concrete crushing due to large compressive strain. A subroutine is developed using macro commands of ANSYS. In this research, Branson's equation or Ie procedure is assumed in the prediction of deflection of retrofitted concrete members. The modifications needed due to laminate bonding are the cracking moments of inertia (Icr) of the beams or slabs bonded with CFRP laminates, which are included in the analysis.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/15083
- Subject Headings
- ANSYS (Computer system), Reinforced concrete--Plastic properties, Carbon composites, Fiber reinforced plastics, Bridges--Design and construction, Prestressed concrete construction
- Format
- Document (PDF)
- Title
- Thermal analysis of a heterojunction bipolar transistor.
- Creator
- Kokkalera, Subbaiya U., Florida Atlantic University, Tsai, Chi-Tay, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The Heterojunction Bipolar Transistor (HBT) is capable of delivering high current density at microwave frequencies and are now being implemented in microwave circuitry as high power amplifiers. The heat generated during device operation is dissipated through the Gallium Arsenide substrate. Because of its poor thermal conductivity the junction temperature rise can be large enough to degrade and thermally limit the performance of the device. The power HBT with multiple emitter fingers are...
Show moreThe Heterojunction Bipolar Transistor (HBT) is capable of delivering high current density at microwave frequencies and are now being implemented in microwave circuitry as high power amplifiers. The heat generated during device operation is dissipated through the Gallium Arsenide substrate. Because of its poor thermal conductivity the junction temperature rise can be large enough to degrade and thermally limit the performance of the device. The power HBT with multiple emitter fingers are susceptible to the thermal effect due to non-uniform temperature distribution. This results in a thermal effect called thermal runaway causing thermal-induced current instability and hot spot formation thus destroying the device. Thermal shunt technique which has been developed to suppress this non-uniform temperature involves fabrication of a thick metal thermal shunt connecting all the fingers thus forming a strong thermal coupling between the emitter fingers. In this thesis 2 and 3-dimensional thermal simulations were carried out using Finite Element techniques to study the thermal behavior of the HBT's as a function of thermal shunt and other device design configurations such as the number of emitter fingers, thickness of thermal shunt, emitter spacing, Silicon as a substrate material, power variation etc. The results are projected as a design guideline for HBT device.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/15081
- Subject Headings
- Junction transistors, Thermal analysis, Microwave circuits
- Format
- Document (PDF)
- Title
- Thickness and weld profile effects upon the fatigue crack development in sea water.
- Creator
- Li, Yong., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This research investigated the plate thickness and weld profile effects upon fatigue of structural steel in sea water. Specific attention was focused on the initiation and propagation behavior of fatigue cracks formed at the toe of different profiled welds and varied plate thicknesses. It was shown that the initiation life was reduced as the thickness increased. The improved weld profile increased the crack initiation life. Analysis of the fatigue data indicated that the Initiation Life to...
Show moreThis research investigated the plate thickness and weld profile effects upon fatigue of structural steel in sea water. Specific attention was focused on the initiation and propagation behavior of fatigue cracks formed at the toe of different profiled welds and varied plate thicknesses. It was shown that the initiation life was reduced as the thickness increased. The improved weld profile increased the crack initiation life. Analysis of the fatigue data indicated that the Initiation Life to Failure Life Ratio Ni/Nf appeared to be greater for the improved weld profile than for the AWS Basic weld profile. The improved weld profile prolonged the propagation life Np. The thickness factor influenced the propagation life Np for the improved weld profile, but the trend was uncertain for the basic weld profile.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14532
- Subject Headings
- Steel, Structural--Fatigue
- Format
- Document (PDF)
- Title
- Thermodynamic analysis of the influences of temperature and pressure on deep sea cathodic protection criterion.
- Creator
- Wang, Weiqing., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Knowledge of the reversible potential for corrosion reaction under condition of deep sea exposure and how this is influenced by parameters such as temperature and pressure is of importance to the understanding and design of deep sea cathodic protection systems, since this potential is used as the cathodic protection criterion. Also, if the polarized potential is more negative than the reversible potential of the hydrogen reaction, then hydrogen embrittlement may occur. Thermodynamic analysis...
Show moreKnowledge of the reversible potential for corrosion reaction under condition of deep sea exposure and how this is influenced by parameters such as temperature and pressure is of importance to the understanding and design of deep sea cathodic protection systems, since this potential is used as the cathodic protection criterion. Also, if the polarized potential is more negative than the reversible potential of the hydrogen reaction, then hydrogen embrittlement may occur. Thermodynamic analysis methods are used to calculate Gibbs free energy change and reversible potential of reactions involved in cathodic protection of steel for temperatures and pressures typical of deep sea. Based on the assumptions employed it is found that the reversible potential for the iron reaction becomes less negative with depth for the first 1000m and remains approximately constant beyond this.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14515
- Subject Headings
- Steel--Cathodic protection, Seawater--Thermodynamics
- Format
- Document (PDF)
- Title
- A STUDY OF THE EFFECT OF FLOW PARAMETERS ON THE CATHODIC PROTECTION OF A STEEL PLATE IN NATURAL SEAWATER.
- Creator
- MCCABE, KEVIN MICHAEL., Florida Atlantic University, Smith, Samuel W., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The influence of hydrodynamic parameters and cathodic polarization on the formation of calcareous deposits on a steel plate in flowing seawater is investigated. Current density variations on the plate are determined for a combination of applied potentials and seawater velocities. Equations are developed to relate the cathodic current density distribution to variations in hydrodynamic and diffusional boundary layer thickness along the plate for laminar and turbulent flow regimes. A comparison...
Show moreThe influence of hydrodynamic parameters and cathodic polarization on the formation of calcareous deposits on a steel plate in flowing seawater is investigated. Current density variations on the plate are determined for a combination of applied potentials and seawater velocities. Equations are developed to relate the cathodic current density distribution to variations in hydrodynamic and diffusional boundary layer thickness along the plate for laminar and turbulent flow regimes. A comparison of experimental current densities on a bare plate to that predicted by theory is examined. Effects of flow on the formation and properties of calcareous deposits are discussed in light of recent developments in marine cathodic protection.
Show less - Date Issued
- 1984
- PURL
- http://purl.flvc.org/fcla/dt/14192
- Subject Headings
- Plates, Iron and steel--Cathodic protection, Carbon steel--Corrosion, Plates, Iron and steel--Fluid dynamics, Cathodic protection
- Format
- Document (PDF)
- Title
- Sensor based mapping and navigation for underwater robots.
- Creator
- Scarim, Philip F., Florida Atlantic University, Steer, Barry, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This thesis presents a mapping and navigation system intended for an unmanned untethered underwater vehicle. The system utilizes range data obtained from a time of flight sonar operating at 307KHz. The range data, along with an angle measurement of the transducer, is used to generate a simple object map (detected object and its position in two dimensions). The raw range data is filtered using an edge detection algorithm. The edge detection algorithm extracts possible corners from the acoustic...
Show moreThis thesis presents a mapping and navigation system intended for an unmanned untethered underwater vehicle. The system utilizes range data obtained from a time of flight sonar operating at 307KHz. The range data, along with an angle measurement of the transducer, is used to generate a simple object map (detected object and its position in two dimensions). The raw range data is filtered using an edge detection algorithm. The edge detection algorithm extracts possible corners from the acoustic data of the scanned environment. The output of the edge detection algorithm is sent to a confidence program. The confidence program determines which of the possible "corners", determined by the edge detection algorithm, are "actual" corners. The output of the confidence program is then used to produce the object map. This object map may be used as the input to an annotated map-builder. The output of the confidence program is then input to the navigation system. The navigation system determines the position of the vehicle relative to a detected object without any a-priori information, which may be used as an input to a path planner and an obstacle avoidance system. The experiments were carried out in a 25 x 30 foot pool and the experimental data processed on a Sun Workstation using Matlab and C generated code for post-processing of the raw acoustical data.
Show less - Date Issued
- 1996
- PURL
- http://purl.flvc.org/fcla/dt/15263
- Subject Headings
- Robots, Underwater navigation
- Format
- Document (PDF)
- Title
- Static, fatigue and ultimate load behavior of bridges prestressed with advanced composite materials.
- Creator
- Sandepudi, Krishna Srinivasa., Florida Atlantic University, Arockiasamy, Madasamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
One of the major problems the construction industry faces today is low corrosion resistance of reinforcing and prestressing steel, which significantly affects the durability of concrete structures. Theoretically Advanced Composite Materials (ACM) can successfully be used in concrete structures, in lieu of steel, as reinforcing and/or prestressing elements, owing to high tensile strength, immunity towards corrosion, low Young's modulus, light weight and high fatigue resistance. Very little...
Show moreOne of the major problems the construction industry faces today is low corrosion resistance of reinforcing and prestressing steel, which significantly affects the durability of concrete structures. Theoretically Advanced Composite Materials (ACM) can successfully be used in concrete structures, in lieu of steel, as reinforcing and/or prestressing elements, owing to high tensile strength, immunity towards corrosion, low Young's modulus, light weight and high fatigue resistance. Very little experimental and performance data are available on the properties of ACM and their application in concrete structures. Thus, to ensure safety of the structures, accurate assessment and continuous performance monitoring of the ACM together with the structure have to be made with an option of active and/or passive structural control. This investigation is aimed to establish the feasibility of using Aramid Fiber Reinforced Plastic (AFRP) cables as reinforcing/prestressing elements in concrete bridge structures. Besides investigating the durability of the AFRP cables in adverse environments (alkali and seawater), static and ultimate load tests were performed on a Double-Tee beam and three rectangular beams together with static, fatigue and ultimate load tests on a half scale model Double-Tee bridge system prestressed with AFRP. The AFRP specimens exposed to alkali and seawater for 900 hours retained 88% of the average failure strength of control specimens. Large deformations at ultimate conditions and good fatigue resistance were observed in the experimental studies. A computer code, FRPFLEX, was developed to perform flexural analysis of beams prestressed/reinforced with the ACM. An incremental, stiffness augmented non-linear analysis was performed using grillage analogy to assess static flexural behavior of Double-Tee bridge system. Analytical results showed good correlation with experimental findings. An active deformation/vibration control model is suggested, which can be incorporated in prototype bridges for safety and performance data evaluation. Feasibility of the use of the AFRP cables in bridge structures is assessed based on the experimental and analytical parameters such as deflections, strains, crack distributions, crack widths and energy considerations.
Show less - Date Issued
- 1995
- PURL
- http://purl.flvc.org/fcla/dt/12414
- Subject Headings
- Prestressed concrete construction, Steel--Fatigue, Bridges--Fatigue, Fiber reinforced plastics
- Format
- Document (PDF)
- Title
- Statistical modeling of the container inventory control in a distribution network.
- Creator
- Feng, Weiming., Florida Atlantic University, Han, Chingping (Jim), College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The study of the reusable container inventory control in a distribution network is crucial to the efficiency and cost effectiveness of the transportation systems. In order to minimize the total operation cost of such a transportation network system, all subsystems of the distribution network have to be optimized together as a whole system. In this study, we extended the inventory control concept and developed a multiple-inventory control model for the transportation network. We presented a...
Show moreThe study of the reusable container inventory control in a distribution network is crucial to the efficiency and cost effectiveness of the transportation systems. In order to minimize the total operation cost of such a transportation network system, all subsystems of the distribution network have to be optimized together as a whole system. In this study, we extended the inventory control concept and developed a multiple-inventory control model for the transportation network. We presented a systematic approach to address all those subsystems as interrelated systems. Mathematical models were developed for the transportation and container inventory control problems first. Then, the statistical modeling method was used to analyze the effects of the container inventory management policies on the performance of the transportation system. Based on the optimization theory, simulation executions were such arranged to lead to the globe optimality. This makes it possible to optimize the variables of inventory control under different control policies without solving mathematical models. A Simulation Code Generator (SCG) was also developed for a general container inventory control system.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/12525
- Subject Headings
- Inventory control--Mathematical models, Containerization, Transportation--Mathematical models, Inventory control--Simulation methods
- Format
- Document (PDF)
- Title
- THE USE OF COMPUTER SIMULATION TECHNIQUES IN THE DESIGN OF SHIP CHANNEL WIDTH (PORT, HARBOR, TAMPA).
- Creator
- THOMAS, CLINTON WILLIAM., Florida Atlantic University, Lin, Newman K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This report presents a detailed approach to the problem of determining expected shipping delays that are caused by inadequate channel width. Data collection and analysis is accomplished for the shipping industry of Tampa Bay, Florida. Historical data and cargo projection are used to develop the expected shipping traffic density and distribution for the year 2000. An overview of a computer model that simulates the shipping traffic and accounts for delays due to channel width is presented. A...
Show moreThis report presents a detailed approach to the problem of determining expected shipping delays that are caused by inadequate channel width. Data collection and analysis is accomplished for the shipping industry of Tampa Bay, Florida. Historical data and cargo projection are used to develop the expected shipping traffic density and distribution for the year 2000. An overview of a computer model that simulates the shipping traffic and accounts for delays due to channel width is presented. A sensitivity analysis performed on the model to determine the effect each input variable has on shipping delays. The results are presented in the form of shipping delay curves for seven types of vessels over a range of channel widths.
Show less - Date Issued
- 1986
- PURL
- http://purl.flvc.org/fcla/dt/14287
- Subject Headings
- Shipping--Simulation methods, Channels (Hydraulic engineering)--Design and construction--Simulation methods, Shipping--Florida--Tampa Bay
- Format
- Document (PDF)
- Title
- THREE-DIMENSIONAL PHOTOELASTIC STRESS ANALYSIS OF A METAL-TO-METAL CONTACT BOLTED FLANGE.
- Creator
- Mahfuz, Hassan, Florida Atlantic University, Case, Robert O., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Three-dimensional photoelastic stress analysis techniques are used to determine the stress distribution in a metal-to-metal contact bolted flange. The flange belongs to a thin-walled stage support casing of a jet aircraft engine. Of special interest is the state of stress experienced at flange separation due to axial and bending loads during severe in-flight maneuvering. Details of model development, data collection and discussion of results for the stresses in the bolts and in the vicinity...
Show moreThree-dimensional photoelastic stress analysis techniques are used to determine the stress distribution in a metal-to-metal contact bolted flange. The flange belongs to a thin-walled stage support casing of a jet aircraft engine. Of special interest is the state of stress experienced at flange separation due to axial and bending loads during severe in-flight maneuvering. Details of model development, data collection and discussion of results for the stresses in the bolts and in the vicinity of the flange are presented.
Show less - Date Issued
- 1986
- PURL
- http://purl.flvc.org/fcla/dt/14319
- Subject Headings
- Strains and stresses, Photoelasticity, Materials--Testing
- Format
- Document (PDF)
- Title
- Trim analysis by shooting and finite elements and Floquet eigenanalysis by QR and subspace iterations in helicopter dynamics.
- Creator
- Achar, Nagari Shriranga., Florida Atlantic University, Gaonkar, Gopal H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The trim analysis for the initial state and control inputs that satisfy response periodicity and flight conditions, and the Floquet eigenanalysis for a few largest eigenvalues of the Floquet transition matrix (FTM) are investigated. In the trim analysis, the convergence of Newton iteration is investigated in computing the periodic initial state and control inputs sequentially and in parallel. The trim analysis uses the shooting method and two h-versions of temporal finite element methods, one...
Show moreThe trim analysis for the initial state and control inputs that satisfy response periodicity and flight conditions, and the Floquet eigenanalysis for a few largest eigenvalues of the Floquet transition matrix (FTM) are investigated. In the trim analysis, the convergence of Newton iteration is investigated in computing the periodic initial state and control inputs sequentially and in parallel. The trim analysis uses the shooting method and two h-versions of temporal finite element methods, one based on displacement formulation and the other on mixed formulation of displacements and momenta. In each method, both the sequential and in-parallel schemes are used, and the resulting nonlinear equations are solved by damped Newton iteration with an optimally selected damping parameter. The reliability of damped Newton iteration, including earlier-observed divergence problems, is quantified by the maximum condition number of the Jacobian matrices of the iterative scheme. For illustrative purposes, rigid flap-lag and flap-lag-torsion models based on quasisteady aerodynamics are selected. Demanding trim analysis conditions are included by considering advance ratios or dimensionless flight speeds twice as high as those of current helicopters. Concerning the Floquet eigenanalysis, the feasibility of using the Arnoldi-Saad method, one of the emerging subspace iteration methods, is explored as an alternative to the currently used QR method, which is not economical for partial eigenanalysis. The reliability of the Arnoldi-Saad method is quantified by the eigenvalue condition numbers and the residual errors of the eigenpairs. In the three trim analysis methods, while the optimally selected damping parameter provides almost global convergence, the in-parallel scheme requires much less machine time than the conventional sequential scheme; both schemes have comparable reliability of the Newton iteration without and with damping. The Arnoldi-Saad method takes much less machine time than the QR method with comparable reliability.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/12297
- Subject Headings
- Helicopters--Dynamics, Helicopters--Handling characteristics, Stability of helicopters--Mathematical models
- Format
- Document (PDF)
- Title
- Ultimate load, creep, shrinkage, and reliability studies of a precast single cell segmental bridge with external post-tensioning.
- Creator
- Murugesh, Ganapathy., Florida Atlantic University, Reddy, Dronnadula V., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This dissertation is a study of a 1:3.5 scale model of an externally post-tensioned single cell segmental bridge model of the Long Key bridge. The behavior of the bridge system was evaluated in terms of deflections, strains, joint openings, etc. under static and ultimate load conditions. The precast segmental bridge was cast, assembled, and tested at the Department of Ocean Engineering, Florida Atlantic University for AASHTO HS20-44 truck loadings at typical locations. The study addressed the...
Show moreThis dissertation is a study of a 1:3.5 scale model of an externally post-tensioned single cell segmental bridge model of the Long Key bridge. The behavior of the bridge system was evaluated in terms of deflections, strains, joint openings, etc. under static and ultimate load conditions. The precast segmental bridge was cast, assembled, and tested at the Department of Ocean Engineering, Florida Atlantic University for AASHTO HS20-44 truck loadings at typical locations. The study addressed the joint opening behavior and the response of external tendons during service and ultimate load levels. The analytical nonlinear behavior of the bridge upto the ultimate load level has been predicted using a finite element software PCFRAME developed at University of California, Berkeley. Creep and shrinkage strains were predicted using computer program CRACK developed at University of Calgary, Canada. Creep and shrinkage coefficients evaluated from short term tests, were used in predicting the long term behavior. A method for reliability analysis of post-tensioned segmental bridges has also been presented for serviceability and ultimate limit state conditions.
Show less - Date Issued
- 1991
- PURL
- http://purl.flvc.org/fcla/dt/14709
- Subject Headings
- Precast concrete construction--Testing, Post-tensioned prestressed concrete construction--Testing, Bridges, Concrete--Models
- Format
- Document (PDF)
- Title
- Placement and Denoising of Total Magnetic Field Sensors Onboard an AUV in Support of Geophysical Navigation.
- Creator
- Cracchiolo, Timothy, Beaujean, Pierre-Philippe, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
-
The objective of this thesis is to study the proper placement and denoising of Total Field Magnetometers (TFM) installed on an Autonomous Underwater Vehicle (AUV), in support of a long-term goal to perform geophysical navigation based on total field magnetic sensing. This new form of navigation works by using the magnetic field of the Earth as a source of reference to find the desired heading. The primary tools used in this experiment are a REMUS 100 AUV, a QuSpin scalar magnetometer, and a...
Show moreThe objective of this thesis is to study the proper placement and denoising of Total Field Magnetometers (TFM) installed on an Autonomous Underwater Vehicle (AUV), in support of a long-term goal to perform geophysical navigation based on total field magnetic sensing. This new form of navigation works by using the magnetic field of the Earth as a source of reference to find the desired heading. The primary tools used in this experiment are a REMUS 100 AUV, a QuSpin scalar magnetometer, and a TwinLeaf vector magnetometer. The Earth’s magnetic field was measured over periods of several hours to determine the range of values it provides under natural conditions. Digital filters were created to digitally reduce fluctuations caused by sources of external interference and sources of internal interference. To mitigate the issue of platform based interference, two methods were examined. These methods involved the use of the Tolles-Lawson model and Wavelet Multiresolution Analysis. The Tolles-Lawson model is used to determine the compensation coefficients from a calibration mission to mitigate the effects from the permanently detected magnetic field, the induced magnetic field, eddy currents. and the geomagnetic field. Wavelet multiresolution analysis follows the same basic steps as Fourier transformations and is used to analyze time series with power sources in motion over a frequency spectrum. Several acquisitions were run with the QuSpin in various locations around and along REMUS, and it was concluded that placing the sensor at the very front of the vessel which is approximately 1.8 [m] from the DC motor, with assistance from wavelet analysis was acceptable for the project.
Show less - Date Issued
- 2022
- PURL
- http://purl.flvc.org/fau/fd/FA00013972
- Subject Headings
- Autonomous underwater vehicles, Magnetometers, Magnetic fields, Remote sensing
- Format
- Document (PDF)
- Title
- Wall Pressure Fluctuation in a Turbulent Channel Flow.
- Creator
- Denissova, Lyubov, Glegg, Stewart, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
-
Turbulent flow is a complex three dimensional system of velocity and pressure fluctuations in a fluid that creates vorticity, eddies and other flow structures. In this study we are specifically concerned with the surface pressure fluctuations below a turbulent boundary layer which is one of the primary sources of panel vibration on aircraft fuselages and ship hulls as well a major issue in ship hydrodynamics. The most accepted analytical approaches to describe the surface pressure...
Show moreTurbulent flow is a complex three dimensional system of velocity and pressure fluctuations in a fluid that creates vorticity, eddies and other flow structures. In this study we are specifically concerned with the surface pressure fluctuations below a turbulent boundary layer which is one of the primary sources of panel vibration on aircraft fuselages and ship hulls as well a major issue in ship hydrodynamics. The most accepted analytical approaches to describe the surface pressure fluctuations are the Chase model [1] for the surface pressure wavenumber spectrum and Goody’s model [2] for the pressure spectrum at a point. The most accurate numerical approach to use is Direct Numerical Simulations (DNS) [3]. In this study we compared Chase and Goody’s models against DNS of a turbulent channel flow in the space–time and wavenumber-frequency domains and estimated regions of convergence between the analytical models and the DNS data.
Show less - Date Issued
- 2022
- PURL
- http://purl.flvc.org/fau/fd/FA00014034
- Subject Headings
- Turbulence, Turbulent boundary layer, Pressure
- Format
- Document (PDF)
- Title
- DEVELOPMENT OF A SLIDING MODE CONTROLLER AND CONTROL ALLOCATION OPTIMIZED FOR ELECTRO-MAGNETIC ACTUATOR LIMITATIONS.
- Creator
- Resio, Daniel, Dhanak, Manhar, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
-
This thesis presents the development a sliding mode controller and vehicle allocation to control a surface vessel platform within a high degree of accuracy. This is part of ongoing development on the WAMV platform at Florida Atlantic University to improve autonomy in marine systems. By developing models for the untested thrusters currently used, the efficacy of a Sliding Mode Controller is evaluated, and a new control allocation developed based on the gradient descent optimization method is...
Show moreThis thesis presents the development a sliding mode controller and vehicle allocation to control a surface vessel platform within a high degree of accuracy. This is part of ongoing development on the WAMV platform at Florida Atlantic University to improve autonomy in marine systems. By developing models for the untested thrusters currently used, the efficacy of a Sliding Mode Controller is evaluated, and a new control allocation developed based on the gradient descent optimization method is developed to manage the thrusters’ constrained angles of thrust generation. The official simulation for the WAMV platform was then modified to include these aspects and the system was tested under wind conditions and was successful in achieving control to waypoints. The gradient descent optimization used for the control allocation did manage to increase the accuracy of both heading and position of the system at convergence. The sliding mode controller navigated to the desired waypoint however maintained oscillations of cross track that were less then 2m and heading error less 20 degrees.
Show less - Date Issued
- 2022
- PURL
- http://purl.flvc.org/fau/fd/FA00014037
- Subject Headings
- Unmanned surface vehicles, Actuators, Sliding mode control
- Format
- Document (PDF)
- Title
- ESTIMATION OF THE PHYSICAL PROPERTIES OF CORRODING REBAR IN REINFORCED CONCRETE USING BIOT-STOLL MODEL INVERSION.
- Creator
- Brogden, Matthew, Beaujean, Pierre-Philippe, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
-
The detection of rebar corrosion in reinforced concrete is important due to the high costs of corrosion related damages to infrastructure. One such method of rebar corrosion lies in the use of non-destructive ultrasonic testing. To date, acoustic methods require either the training of an artificial neural network or a theory of acoustic wave propagation. Using a more complete acoustic model such as the Biot-Stoll model avoids algorithm training requirements by directly modeling the acoustic...
Show moreThe detection of rebar corrosion in reinforced concrete is important due to the high costs of corrosion related damages to infrastructure. One such method of rebar corrosion lies in the use of non-destructive ultrasonic testing. To date, acoustic methods require either the training of an artificial neural network or a theory of acoustic wave propagation. Using a more complete acoustic model such as the Biot-Stoll model avoids algorithm training requirements by directly modeling the acoustic environment. A problem with this method lies in the complexity of the model and the selection of free parameters. The problem of parameter selection is addressed by a series of targeted measurements using ultrasonic transducers on a set of existing reinforced concrete samples placed in a saltwater solution. This data can then be analyzed by a non-linear least squares solver to produce a better fit for the acoustic signal.
Show less - Date Issued
- 2022
- PURL
- http://purl.flvc.org/fau/fd/FA00014032
- Subject Headings
- Reinforcing bars--Corrosion, Reinforced concrete, Acoustics, Ultrasonics
- Format
- Document (PDF)
- Title
- DESIGN, SIMULATION, AND TESTING OF A CVT BASED PTO AND CONTROLLER FOR A SMALL SCALE MHK-TURBINE IN LOW FLOW SPEED OPERATION.
- Creator
- Hall, Adam, Dhanak, Manhar, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
-
The aim of this thesis project was to design, develop, and test, a continuously variable transmission (CVT)-based power take off (PTO) sub-system, and its controller, for a small scale marine hydrokinetic turbine (MHK) developed for low-speed tidal currents. In this thesis, a CVT based PTO and controller was developed for a predefined MHK and validated through simulations. A testing platform was subsequently developed including an emulation system to replicate the MHK for testing of the...
Show moreThe aim of this thesis project was to design, develop, and test, a continuously variable transmission (CVT)-based power take off (PTO) sub-system, and its controller, for a small scale marine hydrokinetic turbine (MHK) developed for low-speed tidal currents. In this thesis, a CVT based PTO and controller was developed for a predefined MHK and validated through simulations. A testing platform was subsequently developed including an emulation system to replicate the MHK for testing of the coupled MHK/PTO system. Laboratory testing of the emulation system, PTO component efficiencies, and full system with controls was then conducted. The results showed the mechanical PTO design to be a valid solution and the control methods to be marginally stable with adequate power conversion at low-speed current conditions. The results also identified future work in continued controller development, alternate PTO component testing, and continued testing in parallel with that being done on the MHK prototype.
Show less - Date Issued
- 2022
- PURL
- http://purl.flvc.org/fau/fd/FA00013977
- Subject Headings
- Marine turbines--Design and construction, Marine turbines--Transmission devices, Marine turbines--Testing
- Format
- Document (PDF)
- Title
- Characterization of A Stereo Vision System For Object Classification For USV Navigation.
- Creator
- Kaplowitz, Chad, Dhanak, Manhar, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
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This experiment used different methodologies and comparisons that helped to determine the direction of future research on water-based perception systems for unmanned surface vehicles (USV) platforms. This would be using a stereo-vison based system. Presented in this work is object color and shape classification in the real-time maritime environment. This was coupled with HSV color space that allowed for different thresholds to be identified and detected. The algorithm was then calibrated and...
Show moreThis experiment used different methodologies and comparisons that helped to determine the direction of future research on water-based perception systems for unmanned surface vehicles (USV) platforms. This would be using a stereo-vison based system. Presented in this work is object color and shape classification in the real-time maritime environment. This was coupled with HSV color space that allowed for different thresholds to be identified and detected. The algorithm was then calibrated and executed to configure the depth, color and shape accuracies. The approach entails the characterization of a stereo-vision camera and mount that was designed with 8.5° horizontal viewing increments and mounted on the WAMV. This characterization has depth, color and shape object detection and its classification. Different shapes and buoys were used to complete the testing with assorted colors and shapes. The main program used was OpenCV which entails Gaussian blurring, Morphological operators and Canny edge detection libraries with a ROS integration. The code focuses on the area size and the number of contours detected on the shape for successes. A summary of what this thesis entails is the installation and characterization of the stereovision system on the WAMV-USV by obtaining specific inputs to the high-level controller.
Show less - Date Issued
- 2022
- PURL
- http://purl.flvc.org/fau/fd/FA00014035
- Subject Headings
- Computer vision, Unmanned surface vehicles
- Format
- Document (PDF)
- Title
- Embodied Biological Computers: Closing The Loop on Sensorimotor Integration of Dexterous Robotic Hands.
- Creator
- Ades, Craig, Engeberg, Erik D., Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
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The sensation of touch is an integral part of using our hands. As different researchers work toward the restoration of afferent sensation in prosthetic hands, it becomes urgent to better understand how an artificial hand’s afferent inputs are affected by the efferent muscular outputs, and vice-versa. Current methods of neuroprosthetic research have many regulatory hurdles, time, cost, and associated risk to the patient. To circumvent these hurdles, we developed a non-invasive, closed-loop (CL...
Show moreThe sensation of touch is an integral part of using our hands. As different researchers work toward the restoration of afferent sensation in prosthetic hands, it becomes urgent to better understand how an artificial hand’s afferent inputs are affected by the efferent muscular outputs, and vice-versa. Current methods of neuroprosthetic research have many regulatory hurdles, time, cost, and associated risk to the patient. To circumvent these hurdles, we developed a non-invasive, closed-loop (CL) neuroprosthetic research platform, integrating artificial tactile signals from an artificial hand with biomimetically-stimulated biological neuronal networks (BNNs) cultured in a multielectrode array (MEA) chamber. These living embodied biological computers (EBCs) can provide a non-invasive alternative for investigating invasive neuroprosthetic interfaces. With them we can explore a variety of control techniques, tactile sensation encoding methods, and neural decoding methods to increase the rate of research in this area with minimal regulatory approval, greatly reduced cost and time, and no risk to the patients. In the first stage of this integration, our EBC was programmed to embody neuronal spiking from spontaneously active “efferent” receptive fields in cultured BNNs as intentional signals for movement. Bursts were transferred to a robotic hand and initiated a tapping motion of the index finger laid in proximity to a surface. Contact elicited artificial sensations, which were registered by a biotac tactile sensor array fit to the robotic fingertip.
Show less - Date Issued
- 2022
- PURL
- http://purl.flvc.org/fau/fd/FA00014092
- Subject Headings
- Artificial hands, Neuroprostheses, Neurotechnology (Bioengineering), Robotics
- Format
- Document (PDF)
- Title
- Swimming control of an underwater vessel with elongated ribbon fin propulsion.
- Creator
- Uddin, Mohammad Irfan, Curet, Oscar M., Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
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Navigation of unmanned underwater vehicles in coastal zones, tight spaces and close to structures such as ports, ship hulls and pipelines remains a difficult challenge. Currently Autonomous Underwater Vehicles (AUVs) use a variety of techniques for motion control, including single thrusters with diving planes or hydrofoils, robotic wrists, or a moving mass. However, these techniques provide limited maneuverability. The objective of this work was to understand the mechanics of elongated fin...
Show moreNavigation of unmanned underwater vehicles in coastal zones, tight spaces and close to structures such as ports, ship hulls and pipelines remains a difficult challenge. Currently Autonomous Underwater Vehicles (AUVs) use a variety of techniques for motion control, including single thrusters with diving planes or hydrofoils, robotic wrists, or a moving mass. However, these techniques provide limited maneuverability. The objective of this work was to understand the mechanics of elongated fin propulsion for swimming and motion control of underwater vehicles. This bio-inspired propulsion is used by several fishes that swim by undulating a thin and elongated median fin that allow them to perform forward and directional maneuvers. In the first chapter we present the literature review as well as the mathematical formulation using thrust vectoring approach to achieve forward and turning maneuvers. In the second chapter, we used a robotic vessel with elongated fin propulsion to determine the thrust scaling and efficiency. Using precise force and swimming kinematics measurements with the robotic vessel, the thrust generated by the undulating fin was found to scale with the square of the relative velocity between the free streaming flow and the wave speed. In addition, a hydrodynamic efficiency is presented based on propulsive force measurements and a model on the power required to oscillate the fin laterally.
Show less - Date Issued
- 2022
- PURL
- http://purl.flvc.org/fau/fd/FA00014117
- Subject Headings
- Autonomous underwater vehicles, Biomimetics, Underwater propulsion
- Format
- Document (PDF)