Current Search: Finite element method (x)
View All Items
Pages
 Title
 Finite element analysis of inhomogeneous waveguides.
 Creator
 Dervain, Suzanne Tai., Florida Atlantic University, Sadiku, Matthew
 Abstract/Description

In this thesis, discretized finite element equations were derived and applied to the solution of electromagnetic fields in homogeneous and inhomogeneous waveguides. To improve the accuracy of the results several approaches were taken. Higher order elements were first introduced in the finite element formulation, then a penalty function was applied with explicit boundary conditions, which limit the appearance of nonphysical solutions. The results obtained from the finite element analysis were...
Show moreIn this thesis, discretized finite element equations were derived and applied to the solution of electromagnetic fields in homogeneous and inhomogeneous waveguides. To improve the accuracy of the results several approaches were taken. Higher order elements were first introduced in the finite element formulation, then a penalty function was applied with explicit boundary conditions, which limit the appearance of nonphysical solutions. The results obtained from the finite element analysis were compared to analytical results when available and found to be very accurate.
Show less  Date Issued
 1988
 PURL
 http://purl.flvc.org/fcla/dt/14448
 Subject Headings
 Finite element method, Wave guides
 Format
 Document (PDF)
 Title
 Evolution and application of a parallel algorithm for explicit transient finite element analysis on SIMD/MIMD computers.
 Creator
 Das, Partha S., Florida Atlantic University, Case, Robert O., Tsai, ChiTay, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The development of a parallel data structure and an associated elemental decomposition algorithm for explicit finite element analysis for massively parallel SIMD computer, the DECmpp 12000 (MasPar MP1) machine, is presented, and then extended to implementation on the MIMD computer, CrayT3D. The new parallel data structure and elemental decomposition algorithm are discussed in detail and is used to parallelize a sequential Fortran code that deals with the application of isoparametric...
Show moreThe development of a parallel data structure and an associated elemental decomposition algorithm for explicit finite element analysis for massively parallel SIMD computer, the DECmpp 12000 (MasPar MP1) machine, is presented, and then extended to implementation on the MIMD computer, CrayT3D. The new parallel data structure and elemental decomposition algorithm are discussed in detail and is used to parallelize a sequential Fortran code that deals with the application of isoparametric elements for the nonlinear dynamic analysis of shells of revolution. The parallel algorithm required the development of a new procedure, called an 'exchange', which consists of an exchange of nodal forces at each time step to replace the standard gatherassembly operations in sequential code. In addition, the data was reconfigured so that all nodal variables associated with an element are stored in a processor along with other element data. The architectural and Fortran programming language features of the MasPar MP1 and CrayT3D computers which are pertinent to finite element computations are also summarized, and sample code segments are provided to illustrate programming in a data parallel environment. The governing equations, the finite element discretization and a comparison between their implementation on Von Neumann and SIMDMIMD parallel computers are discussed to demonstrate their applicability and the important differences in the new algorithm. Various large scale transient problems are solved using the parallel data structure and elemental decomposition algorithm and measured performances are presented and analyzed in detail. Results show that CrayT3D is a very promising parallel computer for finite element computation. The 32 processors of this machine shows an overall speedup of 2728, i.e. an efficiency of 85% or more and 128 processors shows a speedup of 7077, i.e. an efficiency of 55% or more. The CrayT3D results demonstrated that this machine is capable of outperforming the CrayYMP by a factor of about 10 for finite element problems with 4K elements, therefore, the method of developing the parallel data structure and its associated elemental decomposition algorithm is recommended for implementation on other finite element code in this machine. However, the results from MasPar MP1 show that this new algorithm for explicit finite element computations do not produce very efficient parallel code on this computer and therefore, the new data structure is not recommended for further use on this MasPar machine.
Show less  Date Issued
 1997
 PURL
 http://purl.flvc.org/fcla/dt/12500
 Subject Headings
 Finite element method, Algorithms, Parallel computers
 Format
 Document (PDF)
 Title
 Transducer design for underwater acoustic communications using the finite element method.
 Creator
 Jacquemin, JeanPhilippe M. J., Florida Atlantic University, LeBlanc, Lester R.
 Abstract/Description

The behavior of radially polarized freeflooded ring (FFR) transducers is studied for application in underwater acoustic communications. Theoretical models are first presented. Then the finite element method (FEM) is introduced and a FEM model for the FFR transducer is proposed. Experimental data are collected and compared to the simulation results with good correspondence. A series of FEM simulations lead then to optimum geometrical parameters for a finetuned FFR transducer dedicated to...
Show moreThe behavior of radially polarized freeflooded ring (FFR) transducers is studied for application in underwater acoustic communications. Theoretical models are first presented. Then the finite element method (FEM) is introduced and a FEM model for the FFR transducer is proposed. Experimental data are collected and compared to the simulation results with good correspondence. A series of FEM simulations lead then to optimum geometrical parameters for a finetuned FFR transducer dedicated to underwater acoustic communications. Finally, stack transducers models and the piezocomposite technology are presented as possible improvement of the present transducer.
Show less  Date Issued
 2001
 PURL
 http://purl.flvc.org/fcla/dt/12758
 Subject Headings
 Underwater acoustics, Finite element method, Transducers, Interdigital
 Format
 Document (PDF)
 Title
 A midfrequency vibration analysis of a Tbeam.
 Creator
 Fremiot, Thomas., Florida Atlantic University, Cuschieri, Joseph M.
 Abstract/Description

This thesis describes a numerical technique for modeling the vibrational behavior of a complex structure in the midfrequency range. The structure is divided into subsystems, and each subsystem is modeled using Finite Elements. The obtained results are then manipulated to model variations in the response due to nominal variations in the structure. Based on a Component Mode Synthesis representation, the calculations lead to a deterministic energy flow model. The model represents the...
Show moreThis thesis describes a numerical technique for modeling the vibrational behavior of a complex structure in the midfrequency range. The structure is divided into subsystems, and each subsystem is modeled using Finite Elements. The obtained results are then manipulated to model variations in the response due to nominal variations in the structure. Based on a Component Mode Synthesis representation, the calculations lead to a deterministic energy flow model. The model represents the deterministic dynamic behavior of the structure for mid frequencies. However, in mid frequencies, the response is sensitive to perturbations in the properties of the structure. An appropriate way to represent those perturbations is to calculate the response of an ensemble of structures. The ensemble is defined in terms of the statistics of the local natural frequencies. A technique combining a Monte Carlo simulation with the Perturbation approach is used to relate the perturbations in the local natural frequencies to the statistics of the energy flow. This combined method is computationally tractable, being several times faster than a full Monte Carlo simulation of the whole global structure.
Show less  Date Issued
 2001
 PURL
 http://purl.flvc.org/fcla/dt/12739
 Subject Headings
 Concrete beamsVibration, Finite element methods, Monte Carlo method
 Format
 Document (PDF)
 Title
 Detailed stress analysis of a spherical acrylic submersible by 3D finite element modeling.
 Creator
 Das, Partha S., Harbor Branch Oceanographic Institute
 Date Issued
 1999
 PURL
 http://purl.flvc.org/fau/fd/FA00007504
 Subject Headings
 Pressure vessels, Finite element method, Pressure vesselsCracking
 Format
 Document (PDF)
 Title
 Modeling piezoelectric material and ultrasound transducers.
 Creator
 Crimi, Sarah., Harriet L. Wilkes Honors College
 Abstract/Description

We discuss piezoelectric and piezoceramic material as well as ultrasound transducers. We study the analytical methods for calculating the impedance of a simple bar of piezoceramic material and a simple ultrasound transducer, and discuss the methodology behind the numerical technique (Finite Element Method) to model a complex ultrasound transducer. With a simple ultrasound transducer model created in the software program PZex, we find out how the impedance is aected when the scale of the...
Show moreWe discuss piezoelectric and piezoceramic material as well as ultrasound transducers. We study the analytical methods for calculating the impedance of a simple bar of piezoceramic material and a simple ultrasound transducer, and discuss the methodology behind the numerical technique (Finite Element Method) to model a complex ultrasound transducer. With a simple ultrasound transducer model created in the software program PZex, we find out how the impedance is aected when the scale of the relative permittivity is varied. We then create a working model of a complex ultrasound transducer and learn how impedance is affected by varying the size of the electrode driven and adding a propagation layer. We saw that there was not a direct relationship between varying the relative permittivity and the change in impedance as we expected. We saw that varying the size of the electrode and adding a propagation layer created expected impedances.
Show less  Date Issued
 2010
 PURL
 http://purl.flvc.org/FAU/3334250
 Subject Headings
 Piezoelectric transducers, Finite element method, Ultrasonic waves, Microelectromechanical systems
 Format
 Document (PDF)
 Title
 Development of an efficient general purpose cable model and simulation for marine applications.
 Creator
 Radanovic, Branka., Florida Atlantic University, Driscoll, Frederick R., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This work develops, a general numerical model and efficient integration routine to calculate the response of the underwater cable that connects the Lockheed Martin remote minehunting vehicle to its variable depth sensor. The general model is developed from continuous cable equations that are discretized using a finite element method with linear elements. The resulting discrete system of equations is nonlinear and stiff. Thus, we chose the implicit Generalizedalpha method to integrate these...
Show moreThis work develops, a general numerical model and efficient integration routine to calculate the response of the underwater cable that connects the Lockheed Martin remote minehunting vehicle to its variable depth sensor. The general model is developed from continuous cable equations that are discretized using a finite element method with linear elements. The resulting discrete system of equations is nonlinear and stiff. Thus, we chose the implicit Generalizedalpha method to integrate these equations because it possess numerical dissipation. This integration routine is coded into a C++ based numerical simulation and the results and efficiency were compared with the results and efficiency of the RungeKutta method. Based on the validation test cases, Generalizedalpha method proved to be an efficient and reliable integration method for stiff equations governing the motion of underwater cables.
Show less  Date Issued
 2002
 PURL
 http://purl.flvc.org/fcla/dt/12910
 Subject Headings
 Cables, RungeKutta formulas, Finite element method
 Format
 Document (PDF)
 Title
 Development of a variablelength underwater cable model.
 Creator
 Curic, Dusan., Florida Atlantic University, Driscoll, Frederick R.
 Abstract/Description

This thesis develops a novel variable length cable model to simulate the behavior of submerged cables with variable unstretched length and a PC based simulation that integrates the governing cable equations. The general model is developed from continuous cable equations that are discretized using a finite element method with linear elements. Two systems of equations were developed, one for a variable length elastic element and the other for a constant length elastic element. A cable...
Show moreThis thesis develops a novel variable length cable model to simulate the behavior of submerged cables with variable unstretched length and a PC based simulation that integrates the governing cable equations. The general model is developed from continuous cable equations that are discretized using a finite element method with linear elements. Two systems of equations were developed, one for a variable length elastic element and the other for a constant length elastic element. A cable transition model is developed to ensure dynamic compatibility when a variable length element is divided or combined. The model proved to be an efficient and reliable tool to predict the behavior of underwater cables with variable length.
Show less  Date Issued
 2003
 PURL
 http://purl.flvc.org/fcla/dt/12976
 Subject Headings
 Cables, SubmarineMathematical models, Finite element method
 Format
 Document (PDF)
 Title
 Finite element methods for stochastic structures and conditional simulation.
 Creator
 Ren, Yongjian., Florida Atlantic University, Elishakoff, Isaac, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This dissertation deals with the nonperturbative finite element methods for stochastic structures and conditional simulation techniques for random fields. Three different nonperturbative finite element schemes have been proposed to compute the first and second moments of displacement responses of stochastic structures. These three methods are based, respectively, on (i) the exact inverse of the global stiffness matrix for simple stochastic structures; (ii) the variational principles for...
Show moreThis dissertation deals with the nonperturbative finite element methods for stochastic structures and conditional simulation techniques for random fields. Three different nonperturbative finite element schemes have been proposed to compute the first and second moments of displacement responses of stochastic structures. These three methods are based, respectively, on (i) the exact inverse of the global stiffness matrix for simple stochastic structures; (ii) the variational principles for staticallydeterminate beams; and (iii)Â the elementlevel flexibility for general stochastic statically indeterminate structures. The nonperturbative finite element method for stochastic structures possesses several advantages over the conventional perturbationbased finite element method for stochastic structures, including (i) applicability to large values of the coefficient of variation of random parameters; (ii) convergence to exact solutions when the finite element mesh is refined; (iii) requirement of less statistical information than that demanded by the highorder perturbation methods. Conditional simulation of random fields has been an extremely important research field in most recent years due to its application in urban earthquake monitoring systems. This study generalizes the available simulation technique for onevariate Gaussian random fields, conditioned by realizations of the fields, to multivariate vector random field, conditioned by the realizations of the fields themselves as well as the realizations of the fields derivatives. Furthermore, a conditional simulation for nonGaussian random fields is also proposed in this study by combining the unconditional simulation technique of nonGaussian fields and the conditional simulation technique of Gaussian fields. Finally, the dissertation incorporates the simulation technique of random field into the nonperturbation finite element method for stochastic structures, to handle the cases where only onedimensional probability density function and the correlation function of the random parameters are available, the demanded twodimensional probability density function is unavailable. Simulation technique is applied to generate the samples of random fields which are used to estimate the correlation between flexibilities over elements. The estimated correlation of flexibility is then used in finite element analysis for stochastic structures. For each proposed approach, numerous examples and numerical results have been implemented.
Show less  Date Issued
 1998
 PURL
 http://purl.flvc.org/fcla/dt/12580
 Subject Headings
 Finite element method, Stochastic processes, Random fieldsMathematical models
 Format
 Document (PDF)
 Title
 Finite element analysis to study the structural behavior of an underwater acoustic tower.
 Creator
 Sambandam, Sundaresakumar., Florida Atlantic University, Case, Robert O., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This thesis deals with the static analysis of a three dimensional underwater acoustic tower exclusively designed and fabricated by Harbor Branch Oceanographic Institution, Ft. Pierce, Florida. A commercial finite element package COSMOS/M was used for the finite element analysis. The structural modeling as well as processing of the results was performed using GEOSTAR Ver. 1.65 interactive graphics package. The analysis was concentrated on the main instrument pipe carrying the required...
Show moreThis thesis deals with the static analysis of a three dimensional underwater acoustic tower exclusively designed and fabricated by Harbor Branch Oceanographic Institution, Ft. Pierce, Florida. A commercial finite element package COSMOS/M was used for the finite element analysis. The structural modeling as well as processing of the results was performed using GEOSTAR Ver. 1.65 interactive graphics package. The analysis was concentrated on the main instrument pipe carrying the required instruments for data acquisition. Various environmental loading induced by ocean currents, hydrostatic pressure, buoyancy and self weight of the tower have been considered in the analysis. The construction aspects of the tower as well as the finite element analysis of tower substructures are also discussed. The deflection of the tower due to the imposed loading is studied and deflection profiles are drawn.
Show less  Date Issued
 1992
 PURL
 http://purl.flvc.org/fcla/dt/14846
 Subject Headings
 Finite element method, Offshore structures, underwater acousticsData processing
 Format
 Document (PDF)
 Title
 Finite element modeling of composite laminates with embedded piezoelectric structures including debonding.
 Creator
 Suarez, Beatriz., Florida Atlantic University, Tsai, ChiTay, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Piezoelectric sensors are one of the primary devices used in smart structures because of their capability to act as both, sensors and actuators. A finite element model has been developed to predict elastic behavior and electrical response of laminate composites with embedded piezoelectric sensors. Correlations with experimental results indicate that the model is capable of forecasting the elastic and electrical response of the structure with good accuracy. The important issue of debonding of...
Show morePiezoelectric sensors are one of the primary devices used in smart structures because of their capability to act as both, sensors and actuators. A finite element model has been developed to predict elastic behavior and electrical response of laminate composites with embedded piezoelectric sensors. Correlations with experimental results indicate that the model is capable of forecasting the elastic and electrical response of the structure with good accuracy. The important issue of debonding of any of the faces of the sensors is also studied in the current work. Finite element results indicate significant changes in the elastic response caused by debonding, as well as unreliable electrical outputs.
Show less  Date Issued
 1998
 PURL
 http://purl.flvc.org/fcla/dt/15603
 Subject Headings
 Finite element method, Piezoelectric materials, Laminated materials, Smart structures
 Format
 Document (PDF)
 Title
 Identification of support conditions on a beam using finite element analysis.
 Creator
 Ramakrishna, Suresh Babu., Florida Atlantic University, Stevens, Karl K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The equivalent end deflections and rotations for beams with integral, but dissimilar, elastic supports were determined. Finite element analysis was used to generate the midsurface deflection of the beam. Numerical results were then fit to the analytical solution for the deflection of a beam, yielding the equivalent end slope resulting from deformations in the support. The lateral deflection at the support was available directly from the finite element calculation. The approach used for...
Show moreThe equivalent end deflections and rotations for beams with integral, but dissimilar, elastic supports were determined. Finite element analysis was used to generate the midsurface deflection of the beam. Numerical results were then fit to the analytical solution for the deflection of a beam, yielding the equivalent end slope resulting from deformations in the support. The lateral deflection at the support was available directly from the finite element calculation. The approach used for modeling of the supports is discussed. It was found that the slope and deflection at the support increase as the relative stiffness of the support decreases, as would be expected. Results are presented for both cantilever and beams with fixed ends, are valid for slender beams with small deflection.
Show less  Date Issued
 1994
 PURL
 http://purl.flvc.org/fcla/dt/15021
 Subject Headings
 Girders, Finite element method, Elastic analysis (Engineering), Structural analysis (Engineering)
 Format
 Document (PDF)
 Title
 Impact analysis of a piezotransducervibrator.
 Creator
 Karabiyik, Necati., Florida Atlantic University, Tsai, ChiTay, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

PiezoTransducerVibrators are miniature devices that emit both audio and silent signals and are currently targeted for use as an integral part of wristwatch technology. Utilizing nonlinear finite element analysis is essential for obtaining a greater understanding of the system response under varying conditions. Dyna3D nonlinear finite element code is applied in this analysis with the focus on the mechanical aspects of the vibrator. Four impact variables, the velocity, the plate gap, the...
Show morePiezoTransducerVibrators are miniature devices that emit both audio and silent signals and are currently targeted for use as an integral part of wristwatch technology. Utilizing nonlinear finite element analysis is essential for obtaining a greater understanding of the system response under varying conditions. Dyna3D nonlinear finite element code is applied in this analysis with the focus on the mechanical aspects of the vibrator. Four impact variables, the velocity, the plate gap, the weight and the velocity angle are studied to determine the effects on the system response. Each impact variable is assigned three separate values, creating twelve programs for analysis. For each program, responses to impact conditions are studied demonstrating the deformed mode shapes, maximum principal stresses and maximum displacements using state database plots and timehistory plots.
Show less  Date Issued
 1994
 PURL
 http://purl.flvc.org/fcla/dt/15008
 Subject Headings
 Piezoelectric transducers, Finite element method, Wrist watches, Vibrators
 Format
 Document (PDF)
 Title
 Interaction of acoustic waves generated by coupled finite fluidloaded plates.
 Creator
 Kaina, Rachid., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The response of fluidloaded plates has been extensively studied in the past. However, most of the work deals with either infinite plates or finite plates with particular boundary conditions and the results are generally presented only in the limit of small wavelengths compared with the dimensions of the plates. Furthermore, the problem of coupled finite plates where both the acoustic interaction and structural interaction are included in the solution has not been considered. In this...
Show moreThe response of fluidloaded plates has been extensively studied in the past. However, most of the work deals with either infinite plates or finite plates with particular boundary conditions and the results are generally presented only in the limit of small wavelengths compared with the dimensions of the plates. Furthermore, the problem of coupled finite plates where both the acoustic interaction and structural interaction are included in the solution has not been considered. In this dissertation the response of two coupled finite plates set in two alternative configurations is considered. The plates are simply supported on two edges, with arbitrary boundary conditions on the remaining two edges. The solutions obtained for the response of the plates include both the structural interaction at the common junction and the acoustic interaction due to the scattered pressure from each of the two plates. The results are presented in terms of the vibrational power flow into and out of each plate component. The solution is based on a formulation developed in the wavenumber domain combined with the Mobility Power Flow method. Using this approach, different substructural elements coupled under different boundary conditions to form a complex global structure can be considered. The detailed spatial and temporal scales of the structure response are not lost when using this method. In obtaining the solution for the scattering from the fluidloaded plates, a modal decomposition in the direction normal to the simply supported edge is used. A spatial Fouriertransform decomposition is used in the other direction. Due to the finiteness of the plate, eight unknowns parameters are obtained in the transformed result. The solution for these eight unknown parameters is obtained from the boundary conditions and the condition that the response must remain finite. Two analytical approaches are used to solve the final plate integral equation. The first approach consists of an approximation method which obtains a solution based on the solution of the corresponding infinite plate problem. The second approach is a more accurate solution based on the Projection Method for the solution of integral equations. Both of the approaches used in the solution provide accurate predictions at high frequencies. At low frequencies especially for low structural damping or for heavy fluid loading, only the Projection Method gives reliable results. This is attributed to the fact that at low frequencies, the influence of the edges of the plates on the scattering is significant. The overall results obtained from this analysis indicate that the fluid loading and the plate characteristics have a significant influence on the acoustic scattering properties, especially in the case of heavy fluid loading. The application of the method to coupled fluidloaded plates indicates that the junction enhances the scattering properties. The acoustical interaction between the coupled plates increases the contribution to scattering from subsonic wavenumber components. In the absence of the interaction, only supersonic wavenumbers contribute to the scattering. Inclusion of acousticlal interaction requires both supersonic and subsonic components. The significance of the contribution from the subsonic wavenumber components is dependent on the type of the fluid loading.
Show less  Date Issued
 1993
 PURL
 http://purl.flvc.org/fcla/dt/12341
 Subject Headings
 Finite element method, Plates (Engineering), Acoustic emission, SoundTransmission
 Format
 Document (PDF)
 Title
 Investigation of debonding and crack kinking in foam core sandwich beams.
 Creator
 Prasad, Srinivas., Florida Atlantic University, Carlsson, Leif A., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Debond failures in structural sandwich may lead to severe reductions in loadbearing capability of the structure because of impartial transfer of shear and tensile forces between facing and core due to the lack of interfacial bonding. Analysis of interfacial bonding in sandwich specimens subjected to transverse tensile and shear forces is presented. Stress intensity factors computed based on the neartip displacement field are related to experimental crack growth observation on the sandwich...
Show moreDebond failures in structural sandwich may lead to severe reductions in loadbearing capability of the structure because of impartial transfer of shear and tensile forces between facing and core due to the lack of interfacial bonding. Analysis of interfacial bonding in sandwich specimens subjected to transverse tensile and shear forces is presented. Stress intensity factors computed based on the neartip displacement field are related to experimental crack growth observation on the sandwich beams with aluminum skins on a wide range of PVC foam cores. Experimentally it was found that the crack tends to grow at the interface between the bondline and core as opposed to skin/bondline interface. In shear dominated fields, a preexisting flow tended to deflect into the core rather than grow along the interface. The tendency for kinking and the direction of the kink is examined experimentally and analyzed using the finite element method.
Show less  Date Issued
 1993
 PURL
 http://purl.flvc.org/fcla/dt/14861
 Subject Headings
 Finite element method, Sandwich construction, Diffusion bonding (Metals), Fracture mechanics
 Format
 Document (PDF)
 Title
 Studies on crosstalk in microstriplines.
 Creator
 Kopp, Markus Benjamin., Florida Atlantic University, Ungvichian, Vichate, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
 Abstract/Description

This thesis is concerned with the analysis of the current distributions in coplanar parallel microstripline structures, and the calculation of crosstalk in these structures. This is accomplished by using a Finite Element Method approach. Two parallel strips, a right angle bend junction, and a T junction are studied in order to gain an insight into the current distributions and the primary causes of crosstalk. The control of crosstalk is also investigated, with alternative geometries for...
Show moreThis thesis is concerned with the analysis of the current distributions in coplanar parallel microstripline structures, and the calculation of crosstalk in these structures. This is accomplished by using a Finite Element Method approach. Two parallel strips, a right angle bend junction, and a T junction are studied in order to gain an insight into the current distributions and the primary causes of crosstalk. The control of crosstalk is also investigated, with alternative geometries for microstrip designs. It is seen that the finite element method can yield results comparable with other accepted methods, and other perceivable physical models of the test structures. Also shown in the present study that crosstalk can be reduced by decreasing the tracetoground plane separation.
Show less  Date Issued
 1993
 PURL
 http://purl.flvc.org/fcla/dt/14954
 Subject Headings
 Microwave wiring, Crosstalk, Finite element method, Strip transmission lines
 Format
 Document (PDF)
 Title
 Finite safety models for highassurance systems.
 Creator
 Sloan, John C., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
 Abstract/Description

Preventing bad things from happening to engineered systems, demands improvements to how we model their operation with regard to safety. Safetycritical and fiscallycritical systems both demand automated and exhaustive verification, which is only possible if the models of these systems, along with the number of scenarios spawned from these models, are tractably finite. To this end, this dissertation ad dresses problems of a model's tractability and usefulness. It addresses the state space...
Show morePreventing bad things from happening to engineered systems, demands improvements to how we model their operation with regard to safety. Safetycritical and fiscallycritical systems both demand automated and exhaustive verification, which is only possible if the models of these systems, along with the number of scenarios spawned from these models, are tractably finite. To this end, this dissertation ad dresses problems of a model's tractability and usefulness. It addresses the state space minimization problem by initially considering tradeoffs between state space size and level of detail or fidelity. It then considers the problem of human interpretation in model capture from system artifacts, by seeking to automate model capture. It introduces human control over level of detail and hence state space size during model capture. Rendering that model in a manner that can guide human decision making is also addressed, as is an automated assessment of system timeliness. Finally, it addresses state compression and abstraction using logical fault models like fault trees, which enable exhaustive verification of larger systems by subsequent use of transition fault models like Petri nets, timed automata, and process algebraic expressions. To illustrate these ideas, this dissertation considers two very different applications  web service compositions and submerged ocean machinery.
Show less  Date Issued
 2010
 PURL
 http://purl.flvc.org/FAU/2683206
 Subject Headings
 System failures (Engineering), Prevention, Sustainable engineering, Finite element method, Expert systems (Computer science)
 Format
 Document (PDF)
 Title
 Design of cathodic protection using BEM for components of the piilot ocean energy system.
 Creator
 Gantiva, Nicolas., College of Engineering and Computer Science, Florida Atlantic University, Department of Ocean and Mechanical Engineering
 Abstract/Description

The Center for Ocean Energy Technology at Florida Atlantic University is developing an ocean energy turbine system to investigate the feasibility of harnessing Florida's Gulf Stream current kinetic energy and transforming it into a usable form. The turbine system has components which are prone to marine corrosion given the materials they are made of and to the harsh environment they will be exposed to. This study assumes a twopart system composed of a coating system acting as a barrier and...
Show moreThe Center for Ocean Energy Technology at Florida Atlantic University is developing an ocean energy turbine system to investigate the feasibility of harnessing Florida's Gulf Stream current kinetic energy and transforming it into a usable form. The turbine system has components which are prone to marine corrosion given the materials they are made of and to the harsh environment they will be exposed to. This study assumes a twopart system composed of a coating system acting as a barrier and sacrificial anode cathodic protection which polarizes the metal structures to a potential value where corrosion is significantly reduced. Several configurations (varying in anode quantity, size and location) were considered in order to cathodically protect the structures with various coating qualities (poor, good and excellent). These cases were modeled and simulated via Boundary Element Method software and analyzed so as to assess the most appropriate design.
Show less  Date Issued
 2010
 PURL
 http://purl.flvc.org/FAU/2684309
 Subject Headings
 Cathodic protection, Corrosion and anticorrosives, Finite element method, Seawater corrosion, Prevention
 Format
 Document (PDF)
 Title
 A Power Quality Monitoring System for a 20 kW Ocean Turbine.
 Creator
 Cook, Kevin, Xiros, Nikolaos I., Florida Atlantic University
 Abstract/Description

This thesis explores an approach for the measurement of the quality of power generated by the Center of Ocean and Energy Technology's prototype ocean turbine. The work includes the development of a system that measures the current and voltage waveforms for all three phases of power created by the induction generator and quantifies power variations and events that occur within the system. These so called "power quality indices" are discussed in detail including the definition of each and how...
Show moreThis thesis explores an approach for the measurement of the quality of power generated by the Center of Ocean and Energy Technology's prototype ocean turbine. The work includes the development of a system that measures the current and voltage waveforms for all three phases of power created by the induction generator and quantifies power variations and events that occur within the system. These so called "power quality indices" are discussed in detail including the definition of each and how they are calculated using LabYiew. The results of various tests demonstrate that this system is accurate and may be implemented in the ocean turbine system to measure the quality of power produced by the turbine. The work then explores a dynamic model of the ocean turbine system that can be used to simulate the response of the turbine to varying conditions.
Show less  Date Issued
 2010
 PURL
 http://purl.flvc.org/fau/fd/FA00012514
 Subject Headings
 Marine turbinesMathematical models, Fluid dynamics, Power electronics, Finite element method
 Format
 Document (PDF)
 Title
 Hydrodynamic analysis of ocean current turbines using vortex lattice method.
 Creator
 Goly, Aneesh, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The main objective of the thesis is to carry out a rigorous hydrodynamic analysis of ocean current turbines and determine power for a range of flow and geometric parameters. For the purpose, a computational tool based on the vortex lattice method (VLM) is developed. Velocity of the flow on the turbine blades, in relation to the freestream velocity, is determined through induction factors. The geometry of trailing vortices is taken to be helicoidal. The VLM code is validated by comparing its...
Show moreThe main objective of the thesis is to carry out a rigorous hydrodynamic analysis of ocean current turbines and determine power for a range of flow and geometric parameters. For the purpose, a computational tool based on the vortex lattice method (VLM) is developed. Velocity of the flow on the turbine blades, in relation to the freestream velocity, is determined through induction factors. The geometry of trailing vortices is taken to be helicoidal. The VLM code is validated by comparing its results with other theoretical and experimental data corresponding to flows about finiteaspect ratio foils, swept wings and a marine current turbine. The validated code is then used to study the performance of the prototype gulfstream turbine for a range of parameters. Power and thrust coefficients are calculated for a range of tip speed ratios and pitch angles. Of all the cases studied, the one corresponding to tip speed ratio of 8 and uniform pitch angle 20 produced the maximum power of 41.3 [kW] in a current of 1.73 [m/s]. The corresponding power coefficient is 0.45 which is slightly less than the Betz limit power coefficient of 0.5926. The VLM computational tool developed for the research is found to be quite efficient in that it takes only a fraction of a minute on a regular laptop PC to complete a run. The tool can therefore be efficiently used or integrated into software for design optimization.
Show less  Date Issued
 2010
 PURL
 http://purl.flvc.org/FAU/2683131
 Subject Headings
 Marine turbines, Mathematical models, Water currents, Forecasting, Mathematical models, Aerodynamics, Mathematics, Finite element method
 Format
 Document (PDF)