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Title: DESIGN OF A ROBUST MULTIVARIABLE JET ENGINE CONTROL SYSTEM.
Creator: LARKIN, LOUIS JOSEPH., Florida Atlantic University, Duyar, Ahmet, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Until recently, control design techniques for multivariable systems, such as pole placement or optimal control design, have been either too complex to be usable, or yielded designs which were liable to instability if the parameters of the plant varied from those used in the design. A technique which uses the singular values of the system transfer function matrix is now available. This technique yields control designs which are guaranteed to be robust with respect to plant parameter variations...
Show moreUntil recently, control design techniques for multivariable systems, such as pole placement or optimal control design, have been either too complex to be usable, or yielded designs which were liable to instability if the parameters of the plant varied from those used in the design. A technique which uses the singular values of the system transfer function matrix is now available. This technique yields control designs which are guaranteed to be robust with respect to plant parameter variations. This technique, combined with a novel technique for shaping the frequency responses of the singular values is used to design a control system for a gas turbine jet engine. It is shown that adjusting the crossover frequency of the open loop singular values affects the closed loop time and frequency response in the same manner that adjusting the open loop gain affects the response of a single-input/single-output control system.
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Date Issued: 1985
PURL: http://purl.flvc.org/fcla/dt/14235
Subject Headings: Flight control, Jet propulsion--Research
Format: Document (PDF)

Title: The role of calcium-hydroxide in the maintenance of passivity of steel.
Creator: Sohanghpurwala, Ali Akbar S., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The objective of this study was to determine whether the presence of undissolved calcium hydroxide at the steel interface helped maintain or delay the breakdown of passivity under adverse conditions, such as the presence of chlorides and carbonation. Saturated calcium hydroxide solution was used as an electrolyte in the test cell, and steel specimens were exposed to a range of chloride ion concentration and carbonation. The results indicate that undissolved calcium hydroxide has an important...
Show moreThe objective of this study was to determine whether the presence of undissolved calcium hydroxide at the steel interface helped maintain or delay the breakdown of passivity under adverse conditions, such as the presence of chlorides and carbonation. Saturated calcium hydroxide solution was used as an electrolyte in the test cell, and steel specimens were exposed to a range of chloride ion concentration and carbonation. The results indicate that undissolved calcium hydroxide has an important role in the passivation of reinforcing steel. Also, the critical chloride to hydroxide ratio may be more relevant in characterizing the breakdown of passivity than the threshold value of total or soluble chloride present in the electrolyte. It was noted that in the presence of undissolved calcium hydroxide, steel remained passive for as high a chloride ion concentration as 0.54% (by weight of electrolyte).
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Date Issued: 1988
PURL: http://purl.flvc.org/fcla/dt/14429
Subject Headings: Chlorides, Steel--Corrosion
Format: Document (PDF)

Title: The microprocessor design team assignment problem with a new multistage stochastic/Brownian motion model.
Creator: O'Grady, Thomas James., Florida Atlantic University, Han, Chingping (Jim), College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The Microprocessor Design Team Assignment Problem models the microprocessor design efforts of Intel Corporation over a 29-year period from 1972 until 2001. The basic model is a Erlang queuing system based probability model of the individual programming-design team daily operations. After extensive research the Erlang Loss/Delay Blocked Multiserver Model is utilized throughout the dissertation The Erlang loss-delay model takes into account the Key Man Constraint for team leaders and...
Show moreThe Microprocessor Design Team Assignment Problem models the microprocessor design efforts of Intel Corporation over a 29-year period from 1972 until 2001. The basic model is a Erlang queuing system based probability model of the individual programming-design team daily operations. After extensive research the Erlang Loss/Delay Blocked Multiserver Model is utilized throughout the dissertation The Erlang loss-delay model takes into account the Key Man Constraint for team leaders and programming team personnel. The Microprocessor Design Team Assignment Problem Case Study and massive research effort, into Intel Corporations design efforts, is complicated by modeling a major programming-design team operation without any current data or assistance from Intel Corporation. However much of the lack of assistance and data was obtained by utilizing a critical managerial design team decomposition which answered most major questions about Intels lack of adequate personnel and overutilization of team leaders and asst. team leaders throughout the 48 months of most major design projects. The study-dissertation concludes that Intels and Hewlett Packards current positions in the computer industry are relatively secure because of extremely high entry level costs exceeding $850,000,000.00 million dollars. Many individual issues about programming-design team operations are analyzed in a great amount of detail. This is the first time that much of this design-programming team material and information is being made public for future research and continuing improvement upon large scale project managerial methods and techniques. The basic design-programming team effort is also modeled with Erlang probability models and stochastic Riccati differential equations. This modeling effort is discussed in great detail in chapter 5 and Appendix Alpha. It is believed that this fundamental research leads the way for more advanced efforts in manufacturing systems and possibly mechatronics for further models utilizing strong Markov properties. This research effort substantially advances the basic research and knowledge of Partially Observable Markov Decision Processes and Strong Brownian Motion with the basic unit being strong Markov properties.
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Date Issued: 2001
PURL: http://purl.flvc.org/fcla/dt/11962
Subject Headings: Brownian motion processes, Stochastic analysis, Microprocessors
Format: Document (PDF)

Title: The measurement of structural power flow in thin plate structures.
Creator: Padiyar, Satish., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: An analytical and experimental investigation of the flow of vibrational power in a thin, L-shaped, finite plate structure subjected to mechanical and acoustic excitation is presented. In the analytical approach, mobility functions are used to determine the structural intensity vectors at various locations on the plate structure. Simulation results of intensity vectors estimated using three different measurement schemes are compared. The experimentally measured intensity vectors, for the case...
Show moreAn analytical and experimental investigation of the flow of vibrational power in a thin, L-shaped, finite plate structure subjected to mechanical and acoustic excitation is presented. In the analytical approach, mobility functions are used to determine the structural intensity vectors at various locations on the plate structure. Simulation results of intensity vectors estimated using three different measurement schemes are compared. The experimentally measured intensity vectors, for the case of mechanical excitation, using a four accelerometer array, are presented. They are found to match well with the results from the corresponding simulation. Similar results are obtained for the case of acoustic excitation of the L-shaped plate. The general pattern of the structural intensity vectors is found to be in agreement with the expected results.
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Date Issued: 1990
PURL: http://purl.flvc.org/fcla/dt/14678
Subject Headings: Plates (Engineering)--Vibration
Format: Document (PDF)

Title: A method for the optimization of product development resource allocation.
Creator: Worp, Nicholas Jacob., Florida Atlantic University, Han, Chingping (Jim), College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis presents a model designed to optimize the allocation of corporate resources required for the success of a product in the marketplace. The product development resources used in the model are: market research, applied research, product design, cost reduction and advertising. The key goals of this thesis are to provide industry with a usable tool: (1) Implement strategic plans through effective budgeting; (2) Optimize both short and long term profits; (3) Evaluate the impact of...
Show moreThis thesis presents a model designed to optimize the allocation of corporate resources required for the success of a product in the marketplace. The product development resources used in the model are: market research, applied research, product design, cost reduction and advertising. The key goals of this thesis are to provide industry with a usable tool: (1) Implement strategic plans through effective budgeting; (2) Optimize both short and long term profits; (3) Evaluate the impact of resource inter-dependencies; (4) Enable accountability that leads to goal achievement and checks unnecessary growth; (5) Remove much of the negative political and emotional variability; (6) Easily adapt to internal and external changes; (7) Output a specific allocation for each resource as a percentage of sales; (8) Output an estimate of future profitability. Genetic Algorithms are particularly well suited for this application because an exact optima is not required and the search space can be extremely large, complex, and non-linear.
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Date Issued: 1997
PURL: http://purl.flvc.org/fcla/dt/15519
Subject Headings: Genetic algorithms, Resource allocation, Strategic planning, Business planning
Format: Document (PDF)

Title: A model of the horseshoe vortex in juncture flows.
Creator: Monnier, Elie Bertrand., Florida Atlantic University, Dhanak, Manhar R., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: When a boundary-layer flow, either laminar or turbulent, encounters a hemispherical body extending from a surface, a horseshoe-shaped vortex forms at the juncture. In this thesis, we study the evolution of this vortex using a numerical inviscid model and laboratory experiments. The numerical model is based on determining the evolution of the filament using the cut-off method. The assumption is that although the generation of the vortex depends on viscous effects, the dynamic evolution is well...
Show moreWhen a boundary-layer flow, either laminar or turbulent, encounters a hemispherical body extending from a surface, a horseshoe-shaped vortex forms at the juncture. In this thesis, we study the evolution of this vortex using a numerical inviscid model and laboratory experiments. The numerical model is based on determining the evolution of the filament using the cut-off method. The assumption is that although the generation of the vortex depends on viscous effects, the dynamic evolution is well described by inviscid equations of motion. It is found that the vortex filament is fairly steady on the upstream side but on the downstream side, travelling waves appear on it which cannot be suppressed through evolution. For a range of Reynolds number, steady horseshoe-shaped vortex was obtained in the experiments, revealing the shape past the hemisphere. This is compared with the numerical results.
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Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/15326
Subject Headings: Boundary layer, Cascades (Fluid dynamics), Flow visualization, Vortex generators
Format: Document (PDF)

Title: A new methodology in accelerated testing of mechanical heart valve prostheses.
Creator: Wu, Changfu., Florida Atlantic University, Lin, Y. K., Cai, Guo-Qiang, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Mechanical heart valve (MHV) prosthesis is used commonly for clinical replacement of a diseased or dysfunctional natural valve. It is expected to operate uninterruptedly in the human chest for at least 10 years. Classified as Class III medical devices, MHVs of a new design are required by the Food and Drug Administration (FDA) to undergo accelerated durability test for up to 600 million cycles, before a pre-market approval (PMA) can be considered. Knowledge of potential damage/failure...
Show moreMechanical heart valve (MHV) prosthesis is used commonly for clinical replacement of a diseased or dysfunctional natural valve. It is expected to operate uninterruptedly in the human chest for at least 10 years. Classified as Class III medical devices, MHVs of a new design are required by the Food and Drug Administration (FDA) to undergo accelerated durability test for up to 600 million cycles, before a pre-market approval (PMA) can be considered. Knowledge of potential damage/failure mechanisms is of practical interest in assessing the results obtained from accelerated testing. During such tests, an MHV is subjected to higher stresses at higher cycling frequency, and to more severe hydrodynamic environment than those under normal physiological conditions. Three primary factors contributable to damage/failure of an MHV are investigated, namely, contact stresses, water hammer effect, and cavitation. Parametric study is conducted on the contact-induced damage, using the model of a ball-indentation test. Four possible modes of contact damage are identified. Schemes for the selection of appropriate coating parameters to minimize contact stresses in a valve component are discussed. Experimental results of dynamic stresses on a leaflet are presented. The water hammer effect at the instant of valve closure is studied. The destructive force of cavitation is investigated, by incorporating bubble dynamics in a damage tolerance analysis. Cavitation is found to have a greater effect on potential valve damage/failure during accelerated testing. A new measure, cavitation impulse (CI), is introduced to quantify the intensity of MHV cavitation. It is defined as the area under the trace of the high-frequency pressure bursts generated by collapses of cavitation bubbles. CI is modeled as a stationary stochastic process with a discrete parameter (beats), the probability structure of which is estimated from the experimental data. Each CI accounts for both the magnitude and the time-duration of the impinging high pressure of cavitation; therefore, it correlates more closely with cavitation damage on MHV components, thus the time-to-failure (life) of an MHV undergoing testing.
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Date Issued: 2003
PURL: http://purl.flvc.org/fau/fd/FADT12077
Subject Headings: Heart valve prosthesis, Cavitation, Accelerated life testing
Format: Document (PDF)

Title: A structural analysis of the rigging system for an ocean racing yacht.
Creator: Troy, R. Talbot., Florida Atlantic University, Yong, Yan, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A static analysis of the rigging structure for Matador, an 80-ton ocean racing yacht, is performed, and the results are compared to load cell data taken during close haul sailing. The purpose of the analysis is to examine the nature of the loading of the shrouds when heeling, backstay cylinder adjustment and runner tensions are considered. Also, the relative rotation between the shrouds and their joints and possibilities of bending stresses developed by friction are discussed. The sail forces...
Show moreA static analysis of the rigging structure for Matador, an 80-ton ocean racing yacht, is performed, and the results are compared to load cell data taken during close haul sailing. The purpose of the analysis is to examine the nature of the loading of the shrouds when heeling, backstay cylinder adjustment and runner tensions are considered. Also, the relative rotation between the shrouds and their joints and possibilities of bending stresses developed by friction are discussed. The sail forces acting on the mast are calculated with simple foil theory to estimate sail lift coefficients and drag angles. The heeling angle is considered so that weight of mast and rigging is accounted for. The adjustment of the backstay cylinder is simulated by displacement of the lower end of the backstay, and the runner tensions are modeled as point loads on the mast.
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Date Issued: 1990
PURL: http://purl.flvc.org/fcla/dt/14624
Subject Headings: Masts and rigging, Yachts and yachting--Models
Format: Document (PDF)

Title: A study of ambient noise in shallow water.
Creator: Pirie, Rachel Louise., Florida Atlantic University, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis describes a series of measurements that took place over the duration of one year on the South Florida Testing Facility (SFTF) range, Dania, in order to survey the shallow water ambient acoustic environment. Three groups of data sets were taken in December 1998, May 1999 and July 1999. The data was collected using the Ambient Noise Sonar (ANS) that was developed in the Ocean Engineering department at Florida Atlantic University. The ambient acoustic environment was found to be...
Show moreThis thesis describes a series of measurements that took place over the duration of one year on the South Florida Testing Facility (SFTF) range, Dania, in order to survey the shallow water ambient acoustic environment. Three groups of data sets were taken in December 1998, May 1999 and July 1999. The data was collected using the Ambient Noise Sonar (ANS) that was developed in the Ocean Engineering department at Florida Atlantic University. The ambient acoustic environment was found to be highly variable with two main components. Boat noise was found to primarily be associated with the inlet and a source of snapping shrimp situated on the shallow water 30ft reef became apparent through 24hr observation. The effects of adverse weather were not studied due to the absence of this source during the measurement periods.
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Date Issued: 1999
PURL: http://purl.flvc.org/fcla/dt/15738
Subject Headings: Underwater acoustics, Noise--Measurement, Acoustic surface waves
Format: Document (PDF)

Title: A sparse volume array for imaging ocean ambient noise in the near-shore region.
Creator: Olivieri, Marc P., Florida Atlantic University, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Ocean ambient noise has been studied extensively in the past, and several models have been developed to predict its level and to characterize it in different ocean environments. However, most of these studies have been motivated by the need to reduce the negative effect of the ambient noise on measurements. Recently, several studies have used the ambient noise to obtain information about the ocean floor and to achieve passive target detection. This dissertation describes the development of an...
Show moreOcean ambient noise has been studied extensively in the past, and several models have been developed to predict its level and to characterize it in different ocean environments. However, most of these studies have been motivated by the need to reduce the negative effect of the ambient noise on measurements. Recently, several studies have used the ambient noise to obtain information about the ocean floor and to achieve passive target detection. This dissertation describes the development of an Ambient Noise Sonar (ANS) which can be used to measure ambient noise directivity to obtain information about the environment. The system was designed for use on an Autonomous Underwater Vehicle (AUV) and has been used to study the ambient noise in the near shore region by investigating different types of noise in shallow water, such as boat traffic, biological noise and naturally occurring noise up to 20 kHz. There are two advantages to the ANS. First, when mounted on an AUV its mobility will allow the ambient noise to be mapped over an extended area. Second, the very small number of transducers (6 total) used in the array, makes this system suitable for AUV operations because it uses a limited amount of space and power. This dissertation presents the theory of the array processing and preliminary results including examples of boat noise, and biological noise. It was found that the noise from biological sources such as snapping shrimp contributed to the anisotropic component of the acoustic field. These biological sources were found to be concentrated around artificial structures such as piers and groins, and also around natural reefs. Finally noise maps of coastal areas are presented to illustrate the potential of this system to measure the noise field in the coastal region and to evaluate acoustic propagation using passive sources such as the biological noise clusters found along the coast. In the future the ANS will be integrated onto the AUV 'Ocean Explorer II'.
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Date Issued: 1997
PURL: http://purl.flvc.org/fcla/dt/12534
Subject Headings: Underwater acoustics, Acoustic imaging
Format: Document (PDF)

Title: A unified theory of coordination for robotic mechanisms with general parallel or hybrid structures.
Creator: Ling, Shou-Hung., Florida Atlantic University, Huang, Ming Z., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A well designed robot manipulator should have adequate workspace and good static-dynamic performance. It is well known that serial manipulators, while compared to similar size parallel ones, have larger workspace. However, due to their cantilever-like structure, the serial manipulators suffer from the disadvantage of having relatively poor static-dynamic performance. Contrarily, for fully parallel manipulators the good static-dynamic performance comes from the sacrifice of the workspace....
Show moreA well designed robot manipulator should have adequate workspace and good static-dynamic performance. It is well known that serial manipulators, while compared to similar size parallel ones, have larger workspace. However, due to their cantilever-like structure, the serial manipulators suffer from the disadvantage of having relatively poor static-dynamic performance. Contrarily, for fully parallel manipulators the good static-dynamic performance comes from the sacrifice of the workspace. Therefore, manipulators with more general geometries, in particular those with both the serial and the parallel modules, namely the hybrid manipulators, have attracted much of the research attention in robotics recently. While it can be asserted that kinematic theories and techniques are well established for fully serial-chain manipulators, the same assertion cannot be made when they are considered in the above general context. The research described in this dissertation is an undertaking toward the establishment of a general theory of coordination for robotic mechanisms with general parallel or hybrid structures. The scope of this research is concentrated in the kinematics aspect of the aforementioned class of robot manipulators with the main emphasis on the velocity (instantaneous) kinematics. A kinestatic approach, which is based on screw system theory, is adopted in this dissertation. This kinestatic approach leads to the establishment of a fundamental theorem, dubbed as the Parallel Manipulator Coordination Theorem, which integrates the idea of parallel and serial manipulators. Furthermore, the theorem enables us to develop an analysis strategy for systematic formulation and characterization of robotic mechanisms with general parallel (non-redundant) and hybrid geometries. The analysis strategy entails constraints, statics, velocity, and singularity considerations. One distinct advantage of using the screw system theory as the analysis tool is that it facilitates the analysis in a fashion that physical meanings are preserved through out the derivation. The very aspect of preserving the physical meaning distinguishes this method from other algebraically-based and numerically-based methods. An intelligent fault-tolerant system has been studied at the end. The technique and conclusions from the study of parallel manipulator modules have been used to analyze the proposed design.
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Date Issued: 1994
PURL: http://purl.flvc.org/fcla/dt/12385
Subject Headings: Manipulators (Mechanism), Robotics, Kinematics, Screws, Theory of
Format: Document (PDF)

Title: A three-dimensional finite element model for the biomechanical analysis of total ankle replacement.
Creator: Vo, Ha Van., Florida Atlantic University, Han, Chingping (Jim), College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The artificial ankle joint implant has been developed since 1970 after the relatively successful total hip and knee arthroplasty. The main goal of ankle replacement is to eliminate pain and preserve joint motion. Unfortunately, total ankle replacement (TAR) has not been effective as implant of other joints. Recently, published studies of early series showed that the newer second-generation ankle prosthesis have been improved with time. However, only one of the three current ankle designs is...
Show moreThe artificial ankle joint implant has been developed since 1970 after the relatively successful total hip and knee arthroplasty. The main goal of ankle replacement is to eliminate pain and preserve joint motion. Unfortunately, total ankle replacement (TAR) has not been effective as implant of other joints. Recently, published studies of early series showed that the newer second-generation ankle prosthesis have been improved with time. However, only one of the three current ankle designs is allowed by FDA to be used widely in the U.S. This study provides a new ankle design with an advanced approach in designs, biomechanical rationale, and implantation using finite element method (FEM). The new ankle prosthesis in designed to be optimal in terms of ultimate stress, implant parameter that correlating with minimal bone removal using finite element model created from CT scan. In addition, its implantation is less invasive and traumatic compared to the current TAR with longer expecting service life time. Case study showed that the thickness meniscus of the new ankle design obtained from FEM is well within the recommendation ranges by the expert in the ankle joint implantation field.
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Date Issued: 2003
PURL: http://purl.flvc.org/fcla/dt/12052
Subject Headings: Ankle--Effect of implants on, Artificial joints, Ankle--Mechanical properties, Finite element method
Format: Document (PDF)

Title: A petri net framework for the simulation and control of automated systems.
Creator: Murgatroy, Richard John, Jr., Florida Atlantic University, Masory, Oren, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis presents a programming framework in the C language to execute a petri net simulation and real-time control for an automated system. This framework allows for the simulation of a proposed flexible automated system, and also the simultaneous development of the real-time control. The system is based on petri nets, which are used to model the system. Basic petri net theory and the construction of models using petri nets are discussed. The program is designed to allow a hierarchical...
Show moreThis thesis presents a programming framework in the C language to execute a petri net simulation and real-time control for an automated system. This framework allows for the simulation of a proposed flexible automated system, and also the simultaneous development of the real-time control. The system is based on petri nets, which are used to model the system. Basic petri net theory and the construction of models using petri nets are discussed. The program is designed to allow a hierarchical structure to the petri net model, and a modular approach to the program design is taken using some concepts from object oriented programming. The program provides a time-based diagnostic system incorporated into the framework to detect problems during the execution of the actual system. An example application is provided to demonstrate the implementation of the framework to both simulate and control an actual system.
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Date Issued: 1995
PURL: http://purl.flvc.org/fcla/dt/15226
Subject Headings: Petri nets, Computer integrated manufacturing systems--Computer simulation, Flexible manufacturing systems--Computer simulation
Format: Document (PDF)

Title: The prediction of dislocation generation during gallium arsenide crystal growth.
Creator: Liu, Ping., Florida Atlantic University, Tsai, Chi-Tay, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Thermal stresses are induced by temperature variations in gallium arsenide(GaAs) crystal growth. The thermal stresses cause plastic deformations by dislocation and dynamic interaction in the crystal. In this study, firstly the temperature distribution in the Czochralski technique (CZ) growth of GaAs crystal is obtained according to the Jordan model. Secondly a visco-plastic response function for the GaAs crystal is developed from the Haasen model. Finally a nonlinear finite element model is...
Show moreThermal stresses are induced by temperature variations in gallium arsenide(GaAs) crystal growth. The thermal stresses cause plastic deformations by dislocation and dynamic interaction in the crystal. In this study, firstly the temperature distribution in the Czochralski technique (CZ) growth of GaAs crystal is obtained according to the Jordan model. Secondly a visco-plastic response function for the GaAs crystal is developed from the Haasen model. Finally a nonlinear finite element model is employed to simulate the dislocation generation during CZ growth of GaAs crystal.
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Date Issued: 1991
PURL: http://purl.flvc.org/fcla/dt/14780
Subject Headings: Gallium arsenide semiconductors, Dislocations in crystals, Crystal growth
Format: Document (PDF)

Title: A perturbation method for the vibration analysis of beams and plates with free-layer damping treatments.
Creator: Shen, Sueming, Florida Atlantic University, Stevens, Karl K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The feasibility of using structural modification techniques to determine the effect of added viscoelastic damping treatments on the modal properties of a distinct eigenvalue system and a degenerate system is investigated. Linear perturbation equations for the changes introduced into the system eigenproperties are derived and applied to several examples involving the flexural vibration of beams and square plates with varying degrees of damping treatment. Both large and small perturbations are...
Show moreThe feasibility of using structural modification techniques to determine the effect of added viscoelastic damping treatments on the modal properties of a distinct eigenvalue system and a degenerate system is investigated. Linear perturbation equations for the changes introduced into the system eigenproperties are derived and applied to several examples involving the flexural vibration of beams and square plates with varying degrees of damping treatment. Both large and small perturbations are considered. An FEM code has been developed to compute the dynamic system parameters which are subsequently used in an iterative method to determine the modal properties. The perturbation approach described can accommodate temperature and frequency-dependent material properties, and the procedures involved are illustrated in the examples considered. Results obtained for these examples are compared with those available from closed form or finite element solutions, or from experiments. Excellent agreement of the results of the present method with those of other contemporary methods demonstrates the validity, overall accuracy, efficiency and convergence rate of this technique. The perturbation approach appears to be particularly well suited for systems with temperature and frequency dependent material properties, and for design situations where a number of damping configurations must be investigated.
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Date Issued: 1989
PURL: http://purl.flvc.org/fcla/dt/12239
Subject Headings: Girders--Vibration, Plates (Engineering)--Vibration, Perturbation (Mathematics), Damping (Mechanics)
Format: Document (PDF)

Title: pH determination of concrete pore water by a leaching technique for various concrete mixtures.
Creator: Sitton, Izic., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A pH determination technique of concrete pore water by means of leaching OH- ions from powdered samples was developed. This method was then evaluated in terms of sample size, extent of dilution, leaching period, the type of leaching, calcium hydroxide error, and titration scatter. Based upon variations of the above parameters it was concluded that a maximum amount of hydroxide ions was released into solution for samples with the smallest particle size within a 24 hours static leaching period....
Show moreA pH determination technique of concrete pore water by means of leaching OH- ions from powdered samples was developed. This method was then evaluated in terms of sample size, extent of dilution, leaching period, the type of leaching, calcium hydroxide error, and titration scatter. Based upon variations of the above parameters it was concluded that a maximum amount of hydroxide ions was released into solution for samples with the smallest particle size within a 24 hours static leaching period. A 50ml dilution volume proved optimum with regard to filtration and titration. Under the above circumstances calcium hydroxide dissolution did not seem to pose a significant source of error. Furthermore, repeatability of the measurements was good and titration scatter was determined to be about 0.05 pH units. This method was used to determine the pH of samples containing different amounts of fly ash or silica fume additions as well as plain cement (control) samples. A drop in OH- concentration, that is pH, was detected with increasing pozzolanic addition. The results are discussed with the context of the degree of corrosion mitigation afforded by these pozzolans.
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Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/15364
Subject Headings: Concrete--Corrosion, Seawater corrosion, Concrete--Testing, Leaching
Format: Document (PDF)

Title: On the topic of Aerosol Generation and Propagation.
Creator: Schreck, Jesse H., Verma, Siddhartha, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: In this research, three methods of aerosol generation, and their subsequent propagation, are investigated experimentally. These experiments provided insight into the potential risk aerosol can have pertaining to the spread of infectious disease such as COVID – 19. The first of which investigated an alternative generation route that may exist given the discovery of small numbers of viable viruses in urine and stool samples. Flushing biomatter can lead to the aerosolization of micro-organisms;...
Show moreIn this research, three methods of aerosol generation, and their subsequent propagation, are investigated experimentally. These experiments provided insight into the potential risk aerosol can have pertaining to the spread of infectious disease such as COVID – 19. The first of which investigated an alternative generation route that may exist given the discovery of small numbers of viable viruses in urine and stool samples. Flushing biomatter can lead to the aerosolization of micro-organisms; thus, there is a likelihood that bioaerosols generated in public restrooms may pose a concern for the transmission of COVID-19, especially since these areas are relatively confined, experience heavy foot traffic, and may suffer from inadequate ventilation. The results indicate that the particular designs tested in the study generate a large number of droplets in the size range 0.3 𝜇𝑚 – 3 𝜇𝑚, which can reach heights of at least 1.52 m. This highlights the need for incorporating adequate ventilation in the design and operation of public spaces, which can help prevent aerosol accumulation in high occupancy areas and mitigate the risk of airborne disease transmission. Secondly, experiments were conducted to evaluate the effectiveness of facial coverings at various distances around a simulated cough. These concluded that due to the gaps along the seal of a face mask, aerosols can escape 360° around a coughing individual. In the final portion of the thesis study, an experimental method was developed and conducted to break up a droplet via mechanical excitation. The results of these experiments showed that when a droplet is placed on a vibrating string, the droplet can be broken into many secondary droplets which is analogous to one speaking or singing thus providing insight as to how vocal cords can generate respiratory aerosols.
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Date Issued: 2021
PURL: http://purl.flvc.org/fau/fd/FA00013685
Subject Headings: Aerosols, Communicable diseases--Transmission, COVID-19
Format: Document (PDF)

Title: MICROALGAE HARVESTING IN A MICROFLUIDIC CENTRIFUGAL SEPARATOR FOR ENHANCED BIOFUEL PRODUCTION.
Creator: Kavosi, Mohammadhassan, Kim, Myeongsub, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: Among various sources for biofuels, microalgae provide at least three-orders-of-magnitude higher production rate of biodiesel at a given land area than conventional crop-based methods. However, microalgal biodiesel still suffers from significantly lower harvesting efficiency, making such a fuel less competitive. To increase the separation efficiency of microalgae from cultivation solution, an orbital microchannel was utilized that enabled the isolation of biofuel-algae particles from the...
Show moreAmong various sources for biofuels, microalgae provide at least three-orders-of-magnitude higher production rate of biodiesel at a given land area than conventional crop-based methods. However, microalgal biodiesel still suffers from significantly lower harvesting efficiency, making such a fuel less competitive. To increase the separation efficiency of microalgae from cultivation solution, an orbital microchannel was utilized that enabled the isolation of biofuel-algae particles from the effluent. The results obtained showed that the separation efficiency in the microfluidic centrifugal separator can be as high as 76% within a quick separation time of 30 seconds. Multiple parameters of algae behaviors and separation techniques such as initial concentration, pH and temperature were studied and manipulated to achieve better efficiencies. It was found that changing these factors altered the separation efficiency by increasing or decreasing flocculation, or “clumping” of the microalgae within the microchannels. The results suggested that an acidic condition would enhance the separation efficiency since in a basic environment, large flocs of microalgae would block and hinder the separation process. Furthermore, a hot temperature solution (around 33 °C) yielded to a higher separation efficiency. The important characteristics of the separator geometry and the infusion rate on algae separation were also very effective in the separation process. This study revealed that there is an opportunity to improve the currently low efficiency of algae separation in centrifugal systems using much smaller designs in size, ensuring a much more efficient algae harvesting.
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Date Issued: 2021
PURL: http://purl.flvc.org/fau/fd/FA00013745
Subject Headings: Microfluidics, Biofuels, Microalgae, Biodiesel fuels, Separation (Technology)
Format: Document (PDF)

Title: TRAJECTORY PLANNING WITH DYNAMICS-AWARE PARABOLIC BLENDS.
Creator: Moscicki, Travis, Ellenrieder, Karl von, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: This thesis presents the concept of dynamics-aware parabolic blends for an unmanned surface vehicle. Typically, trajectory generation techniques consider only kinematic constraints on a vehicle. By transforming the equations of motion for a surface vehicle to the body fixed frame, the dynamical constraints on the system are more intuitively integrated into the trajectory generator, when compared to working in the Earth fixed frame. Additionally, the accelerations, velocities, and positions...
Show moreThis thesis presents the concept of dynamics-aware parabolic blends for an unmanned surface vehicle. Typically, trajectory generation techniques consider only kinematic constraints on a vehicle. By transforming the equations of motion for a surface vehicle to the body fixed frame, the dynamical constraints on the system are more intuitively integrated into the trajectory generator, when compared to working in the Earth fixed frame. Additionally, the accelerations, velocities, and positions generated by the parabolic blend algorithm are incorporated into the dynamic equations of motion for the vehicle to provide the feedforward control input of a two degree of freedom control law. The feedback control input of the two degree of freedom scheme is an integral sliding mode control law, which tracks the error between the vehicle state and the desired states generated by the novel parabolic blend technique. The approach is numerically validated through simulation, where the described control law demonstrates a 71.93% reduction in error when compared to a standard proportional-derivative control law subjected to the same desired trajectory. Furthermore, on water experiments were performed using both a proportional-derivative control law and an integral sliding mode control law. Both showed the ability to track the proposed parabolic blend approach.
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Date Issued: 2021
PURL: http://purl.flvc.org/fau/fd/FA00013748
Subject Headings: Unmanned vehicles, Trajectories
Format: Document (PDF)

Title: Non-Invasive Measurement Methods for Transient Flows in Wind Tunnels.
Creator: Marcheggiani, Joseph P., Glegg, Stewart, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: A non-invasive transient state measurement method for wind tunnels would be very valuable as an experimental tool. Traditional measurement techniques for transient flows, e.g., hot wire anemometry, require sensors that are placed in the flow. Alternatively, particle image velocimetry (PIV) may be used to measure transient flows non intrusively, but applying PIV requires sensors that are expensive, and it may take months to process the data. The non-invasive measurement techniques considered...
Show moreA non-invasive transient state measurement method for wind tunnels would be very valuable as an experimental tool. Traditional measurement techniques for transient flows, e.g., hot wire anemometry, require sensors that are placed in the flow. Alternatively, particle image velocimetry (PIV) may be used to measure transient flows non intrusively, but applying PIV requires sensors that are expensive, and it may take months to process the data. The non-invasive measurement techniques considered in this thesis utilize sensors that are imbedded into the wall of a wind tunnel, or the response of a Kevlar walled wind tunnel to obtain the pressure time histories of a transient flow. These measurements are suitable and accurate for analyzing steady state flows but the feasibility of using them on time varying flows has yet to be explored. If this method proves possible, it would be very beneficial even if it is less accurate than current invasive methods because it would give results in real time. This thesis investigates a simple transient flow of the startup vortex of an airfoil caused by a step change in angle of attack. Based on thin airfoil theory, two models of an airfoil were created. It was determined that the response of a Kevlar wall can measure the unsteady lift of an airfoil.
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Date Issued: 2021
PURL: http://purl.flvc.org/fau/fd/FA00013837
Subject Headings: Wind tunnels, Transient flow (Aerodynamics), Measurement, Sensors
Format: Document (PDF)

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