Current Search: Cuschieri, Joseph M. (x)
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- Title
- Data and information communication through piping network.
- Creator
- El Moutia, Elhoussain., Florida Atlantic University, Cuschieri, Joseph M., Smith, Samuel M.
- Abstract/Description
-
The purpose of this thesis is to investigate the ability of using piping networks as a communication channel using power line communication transceivers. Two ways by which a piping network is able to propagate waves are investigated. The first wave propagation method is through the pipe shell. Using structural waves and PZT type transducers, data packets are sent and received through the propagation of structural waves in the pipe shell. However, because of the dispersive behavior of quasi...
Show moreThe purpose of this thesis is to investigate the ability of using piping networks as a communication channel using power line communication transceivers. Two ways by which a piping network is able to propagate waves are investigated. The first wave propagation method is through the pipe shell. Using structural waves and PZT type transducers, data packets are sent and received through the propagation of structural waves in the pipe shell. However, because of the dispersive behavior of quasi flexural radial waves, the data packets are distorted. The second wave propagation method explored is acoustic waves in the enclosed fluid. The data packets are sent and received along the piping network using three types of hydrophones. The reliability of this method depends mostly on the sensitivity of the hydrophones.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15392
- Subject Headings
- Piping, Telecommunication systems
- Format
- Document (PDF)
- Title
- Transmission of vibrational power in joined structures.
- Creator
- Gibert, Thierry M., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
The objective of this thesis is the investigation of the transmission of vibrational power between beam-like and plate-like structures with joints using Statistical Energy Analysis (SEA) and an experimental approach. In the case of the L-shaped plate the influence of different structure parameters is investigated to determine possible ways to reduce both the transmitted power and the noise radiated by the receiver structure. The total transmitted power is measured and compared to theoretical...
Show moreThe objective of this thesis is the investigation of the transmission of vibrational power between beam-like and plate-like structures with joints using Statistical Energy Analysis (SEA) and an experimental approach. In the case of the L-shaped plate the influence of different structure parameters is investigated to determine possible ways to reduce both the transmitted power and the noise radiated by the receiver structure. The total transmitted power is measured and compared to theoretical predictions. Also power maps are generated which show the transmission of vibrational power from the source beam to the receiver beam. In the power flow measurements three different techniques are implemented with similar results which all match the analytical results.
Show less - Date Issued
- 1988
- PURL
- http://purl.flvc.org/fcla/dt/14436
- Subject Headings
- Vibration, Power transmission
- Format
- Document (PDF)
- Title
- Design and implementation of an adaptive control system for active noise control.
- Creator
- Duprez, Adrien Eric., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
This thesis describes the design and implementation of an adaptive control system for active noise control. The main approaches available for implementing an active noise controller are presented and discussed. A Least Mean Squares (LMS) based algorithm, the Filtered-X LMS (FXLMS) algorithm, is selected for implementation. The significance of factors, such as delays, system output noise, system complexity, type and size of adaptive filter, frequency bandwidth, etc..., which can limit the...
Show moreThis thesis describes the design and implementation of an adaptive control system for active noise control. The main approaches available for implementing an active noise controller are presented and discussed. A Least Mean Squares (LMS) based algorithm, the Filtered-X LMS (FXLMS) algorithm, is selected for implementation. The significance of factors, such as delays, system output noise, system complexity, type and size of adaptive filter, frequency bandwidth, etc..., which can limit the performance of the adaptive control, is investigated in simulations. For hardware implementation, a floating-point DSP is selected to implement the adaptive controller. The control program and its implementation on the DSP are discussed. The program is first tested with a hardware-in-the-loop set-up and then implemented on a physical system. Active Noise Control in a duct is finally successfully demonstrated. The hardware and the results are discussed.
Show less - Date Issued
- 2001
- PURL
- http://purl.flvc.org/fcla/dt/12771
- Subject Headings
- Adaptive control systems, Active noise and vibration control
- Format
- Document (PDF)
- Title
- Modeling the forward look sonar.
- Creator
- Barrault, Guillaume., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
A numerical model that simulates the operation of a Forward Look Scan Sonar (FLSS) has been developed in this thesis. The model discretizes the sonar-projected signal by a set of rays using a geometrical approach. Bending of the rays due to varying acoustic wave speed is neglected. Simulated raw sonar data are generated, and used as input in the sonar processing algorithms to generate sonar images. Using the model, the influence of, the most critical characteristics of the sonar, including...
Show moreA numerical model that simulates the operation of a Forward Look Scan Sonar (FLSS) has been developed in this thesis. The model discretizes the sonar-projected signal by a set of rays using a geometrical approach. Bending of the rays due to varying acoustic wave speed is neglected. Simulated raw sonar data are generated, and used as input in the sonar processing algorithms to generate sonar images. Using the model, the influence of, the most critical characteristics of the sonar, including phase variations among the channels, non-homogeneous channel amplitude, and the number of bad channels, on the quality of the sonar image is determined. The results of the model are compared to real data from a low frequency FLS sonar (250 KHz) and a high frequency FLS sonar (600 KHz). There is good matching between the simulation and the operation of the two sonars and the performance was markedly enhanced by using the modeling results.
Show less - Date Issued
- 2001
- PURL
- http://purl.flvc.org/fcla/dt/12733
- Subject Headings
- Sonar, Underwater acoustics, Remote submersibles
- Format
- Document (PDF)
- Title
- Modeling the acoustic signature of an Ocean Explorer class autonomous underwater vehicle.
- Creator
- Debiesme, Francois-Xavier., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
Autonomous Underwater Vehicles (AUV) rely on acoustics for a number of mission functions such as communications (Acoustic Modem) and vision (Forward and Side Looking Sonars). The AUV acoustic signature (self-noise and vibration) can thus interfere with AUV operations. Additionally, underwater measurements such as turbulence measurements can be contaminated by interference between the AUV generated acoustics pressures and the low pressures of the turbulence. In this thesis a Finite Element and...
Show moreAutonomous Underwater Vehicles (AUV) rely on acoustics for a number of mission functions such as communications (Acoustic Modem) and vision (Forward and Side Looking Sonars). The AUV acoustic signature (self-noise and vibration) can thus interfere with AUV operations. Additionally, underwater measurements such as turbulence measurements can be contaminated by interference between the AUV generated acoustics pressures and the low pressures of the turbulence. In this thesis a Finite Element and Boundary Element approach is developed to characterize the self-noise (vibration and radiated sound pressure) of a simplified FAU Ocean Explorer AUV. Mechanical excitation from the "podule", which contains the motors for the propulsion and motion control, is assumed in the analysis. The low frequency (less than 1Khz) results are dominated by two types of modes. One type associated with the motion of the "podule" as a rigid body on the vibration isolation supports that connects it to the rest of the AUV structure. The second type is associated with local structural deformations of the "podule", support frame, and AUV hull. Modifying the stiffness of the supports reduces the frequency of the rigid body modes of the "podule", but does not influence the frequencies of the local structural deformations of the "podule" and the rest of the AUV. Decreasing the stiffness of the supports should result in a reduced AUV acoustic signature.
Show less - Date Issued
- 2000
- PURL
- http://purl.flvc.org/fcla/dt/15764
- Subject Headings
- Oceanographic submersibles, Underwater acoustics, Acoustic models
- Format
- Document (PDF)
- Title
- PRESSURE FLUCTUATION MEASUREMENT TECHNIQUES IN A CIRCULAR DUCT WITH INCOMPRESSIBLE TURBULENT FLOW (FREQUENCY-WAVENUMBER SPECTRA).
- Creator
- DAVIS, HARRY LEE., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
Turbulent pressure fluctuations and acoustical shock waves formed at pipe discontinuities are the primary source of flow noise. fhe pipe response is excited by the fluctuating forces associated with the turbulent pressure fluctuations. The forcing functions can be determined from the frequency-wavenumber spectrum of the pressure fluctuations. A procedure is developed here to obtain the frequency-wavenumber spectrum due to fully developed turbulent flow. The data analysis procedures developed...
Show moreTurbulent pressure fluctuations and acoustical shock waves formed at pipe discontinuities are the primary source of flow noise. fhe pipe response is excited by the fluctuating forces associated with the turbulent pressure fluctuations. The forcing functions can be determined from the frequency-wavenumber spectrum of the pressure fluctuations. A procedure is developed here to obtain the frequency-wavenumber spectrum due to fully developed turbulent flow. The data analysis procedures developed in this study to analyze the pressure fluctuations provide a good means to determine the frequency-wavenumber spectrum and represent this data in a clear form. Frequency-wavenumber spectra have been obtained for simulated pressure data. In the experimental system designed to collect turbulent pressure data, it was determined that a recessed transducer configuration cannot be used in water pipe flow turbulent pressure fluctuation studies because of the enhanced turbulence created by the upstream holes. Therefore, flush mounted transducers are required.
Show less - Date Issued
- 1986
- PURL
- http://purl.flvc.org/fcla/dt/14330
- Subject Headings
- Turbulence--Measurement, Fluid dynamics
- Format
- Document (PDF)
- Title
- Power flow analysis of a structure subjected to distributed excitation.
- Creator
- Cimerman, Benjamin Pierre., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
An analytical investigation based on the Power Flow Method is presented for the prediction of vibrational Power Flow in simple connected structures subjected to various forms of distributed excitations. The principle of the power flow method consists of dividing the global structure into a series of substructures which can be analyzed independently and then coupled through the boundary conditions. Power flow expressions are derived for an L-shaped plate structure, subjected to any form of...
Show moreAn analytical investigation based on the Power Flow Method is presented for the prediction of vibrational Power Flow in simple connected structures subjected to various forms of distributed excitations. The principle of the power flow method consists of dividing the global structure into a series of substructures which can be analyzed independently and then coupled through the boundary conditions. Power flow expressions are derived for an L-shaped plate structure, subjected to any form of distributed mechanical excitation or excited by an acoustic plane wave. In the latter case air loading is considered to have a significant effect on the power input to the structure. Fluid-structure interaction considerations lead to the derivation of a corrected mode shape for the normal velocity, and the determination of the scattered pressure components in the expressions for the Power Flow.
Show less - Date Issued
- 1990
- PURL
- http://purl.flvc.org/fcla/dt/14578
- Subject Headings
- Structural dynamics, Plates (Engineering)--Vibration
- Format
- Document (PDF)
- Title
- A STUDY OF FRICTION DAMPING AS APPLIED TO VIBRATING STRUCTURES.
- Creator
- DESAI, VIJAY R., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
Of the many methods of introducing damping in vibrating structures, the dissipation of energy due to interfacial slip can significantly increase the damping loss factor. However, because of the lack of understanding and other phenomena such as fretting corrosion and loss of structural rigidity, friction damping is rarely used. A study was thus undertaken to investigate this complex phenomenon, with emphasis on trying to gain a better understanding of friction damping with certain parameters...
Show moreOf the many methods of introducing damping in vibrating structures, the dissipation of energy due to interfacial slip can significantly increase the damping loss factor. However, because of the lack of understanding and other phenomena such as fretting corrosion and loss of structural rigidity, friction damping is rarely used. A study was thus undertaken to investigate this complex phenomenon, with emphasis on trying to gain a better understanding of friction damping with certain parameters such as clamping pressure, frequency, magnitude of excitation and surface finish. Although the non-linearities associated with friction makes this mechanism difficult to model mathematically, finite element (FE) analysis shows some promise. Although the results obtained using an FE model were not exactly comparable to the experimental results, these analytical results did show the same general trends as observed in the experiments.
Show less - Date Issued
- 1987
- PURL
- http://purl.flvc.org/fcla/dt/14369
- Subject Headings
- Damping (Mechanics), Vibration
- Format
- Document (PDF)
- Title
- Vibrational analysis of a journal bearing.
- Creator
- Journeau, Franck Daniel., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
A Statistical Energy Analysis (SEA) approach is used to investigate the vibrational behavior of a journal bearing. In developing the SEA model, consideration is given to the determination of coupling loss factors between non-conservatively coupled substructures. In the case of the journal bearing, the oil film between the rotating shaft and the bearing liner represents non-conservative coupling. The coupling loss factors are estimated using experimentally measured point mobility functions....
Show moreA Statistical Energy Analysis (SEA) approach is used to investigate the vibrational behavior of a journal bearing. In developing the SEA model, consideration is given to the determination of coupling loss factors between non-conservatively coupled substructures. In the case of the journal bearing, the oil film between the rotating shaft and the bearing liner represents non-conservative coupling. The coupling loss factors are estimated using experimentally measured point mobility functions. The internal loss factors are directly measured with the bearing structure disassembled. Additionally, estimates for the coupling and internal loss factors are obtained in-situ using an energy ratio approach. Using the determined coupling and internal loss factors in an SEA model, estimates for the average mean square velocities on the surface of the bearing subcomponents are obtained for both static and dynamics conditions. The SEA estimates match well with directly measured results for the spatial average surface velocities at medium to high frequencies.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/14786
- Subject Headings
- Journal bearings, Machinery--Noise, Couplings, Vibration
- Format
- Document (PDF)
- Title
- In-plane and out-of-plane components of structural intensity in thick structures.
- Creator
- Grandclement, Cyrille Nicolas., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
In thick structures, vibrational power can propagate by both in-plane and out-of-plane waves. In performing measurements of power flow or structural intensity, it would be required that the components associated with the in-plane or out-of-plane waves be identified. Using a frequency wavenumber approach, the measured structural intensity can be decomposed into its different wave components. In this thesis, simulated structural intensity measurements are presented to demonstrate the use of...
Show moreIn thick structures, vibrational power can propagate by both in-plane and out-of-plane waves. In performing measurements of power flow or structural intensity, it would be required that the components associated with the in-plane or out-of-plane waves be identified. Using a frequency wavenumber approach, the measured structural intensity can be decomposed into its different wave components. In this thesis, simulated structural intensity measurements are presented to demonstrate the use of this frequency wavenumber technique. The results obtained show the distribution of the structural intensity into the wave components. The implementation of this technique using a laser based instrument is discussed. The required characteristics of the instrument, the number of channels, the spacing between the channels, and the phase accuracy, are described. Also, a table to perform the scanning for the frequency wavenumber analysis is presented.
Show less - Date Issued
- 1991
- PURL
- http://purl.flvc.org/fcla/dt/14707
- Subject Headings
- Structural dynamics, Structural analysis (Engineering)
- Format
- Document (PDF)
- Title
- Experimental analysis of the AUV acoustic signature.
- Creator
- Frandsen, Susan Eileen., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
This thesis presents an experimental analysis of the acoustic signature of an Ocean Explorer class AUV. The experimental analysis consists of three parts. The first part reports the measurements performed in an open water environment at NSWC in Lake Pend Oreille, Idaho. The second part reports on measurements performed at the FAU test tank on a mock model of the AUV and the third part reports the measurements also in the FAU test tank of the AUV under typical operating conditions. The model...
Show moreThis thesis presents an experimental analysis of the acoustic signature of an Ocean Explorer class AUV. The experimental analysis consists of three parts. The first part reports the measurements performed in an open water environment at NSWC in Lake Pend Oreille, Idaho. The second part reports on measurements performed at the FAU test tank on a mock model of the AUV and the third part reports the measurements also in the FAU test tank of the AUV under typical operating conditions. The model measurement results were also used to verify the prediction capabilities of a numerical FE model of the AUV using the reciprocity method. The measurements in the FAU tank considered different operating conditions and different mounting of the podule inside the AUV. The podule contains the main mechanical components of the AUV, which are the propulsion motor and the control surface motors. Also considered in these measurements is the influence of the propeller and the influence of covering the aft section of the AUV with a compliant layer. The results of this analysis show that the type of mounting of the podule is not very significant and that significant energy is transferred through the water trapped in between the podule and the hull. Furthermore, the propeller has a significant influence on the acoustic signature since it generates distinct tones. These tones were also observed in the results of the open water measurements.
Show less - Date Issued
- 2001
- PURL
- http://purl.flvc.org/fcla/dt/12768
- Subject Headings
- Underwater acoustics, Oceanographic submersibles
- Format
- Document (PDF)
- Title
- Mobility power flow analysis of connected thick plates with a step discontinuity.
- Creator
- Faivre d'Arcier, Eric., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
In this thesis the flow of vibration power between two coupled, finite plates of arbitrary thicknesses is considered using a Mobility Power Flow (MPF) approach. The plate structure is divided into substructures and mobility functions are determined for the independent substructures. Power flow expressions are derived based on continuity of forces and displacements. The solution presented here considers the effects of both in-plane waves and out-of-plane waves. The solution is applicable to...
Show moreIn this thesis the flow of vibration power between two coupled, finite plates of arbitrary thicknesses is considered using a Mobility Power Flow (MPF) approach. The plate structure is divided into substructures and mobility functions are determined for the independent substructures. Power flow expressions are derived based on continuity of forces and displacements. The solution presented here considers the effects of both in-plane waves and out-of-plane waves. The solution is applicable to frequencies below the first mode of thickness-shear vibration. The results obtained show that at low frequencies, the out-of-plane waves dominate in the transmission of vibrational power. However, at high frequencies or for thick plates, the in-plane waves play a significant role in the power transmission through the plate.
Show less - Date Issued
- 1991
- PURL
- http://purl.flvc.org/fcla/dt/14705
- Subject Headings
- Vibration--Measurement
- Format
- Document (PDF)
- Title
- Mobility power flow analysis of an infinite cylindrical shell with an enclosed plate discontinuity.
- Creator
- Buchmann, Patrick Pierre., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
A mobility power flow approach is used to study the response of an infinitely-long cylindrical shell with an internal plate discontinuity. The shell is excited by either a ring radial force or by a plane acoustic wave. The junction between the shell and the internal plate is assumed to be radially pinned such that in-plane waves of the plate can be neglected. The junction forces are expressed in terms of the mobility functions of the plate and the shell. From knowledge of the junction forces...
Show moreA mobility power flow approach is used to study the response of an infinitely-long cylindrical shell with an internal plate discontinuity. The shell is excited by either a ring radial force or by a plane acoustic wave. The junction between the shell and the internal plate is assumed to be radially pinned such that in-plane waves of the plate can be neglected. The junction forces are expressed in terms of the mobility functions of the plate and the shell. From knowledge of the junction forces and velocities, the power input, the power flow from the shell to the plate, the shell response and the radiated far-field scattered pressure are determined for the circumferential mode n = 0. The results show how the energy propagates from one structure to the other, and present a very clear picture of the characteristics of the scattering pattern from the junction forces.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/15113
- Subject Headings
- Shells (Engineering)--Vibration, Plates (Engineering)--Vibration, Structural dynamics, Vibration
- Format
- Document (PDF)
- Title
- Middle frequency target characteristics.
- Creator
- Castagnet, Sabine., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
The problem of inverse scattering where the scattering structure is unknown, and the physical properties are predicted from the measured echo when the target is insonified with known waveforms, is investigated in this thesis. The scattering structure studied is a submerged, evacuated, spherical elastic shell. The formulation of the echo is carried out using thin shell theory for low and middle frequency range, which basically assumes that shear stresses are negligible. The echo is...
Show moreThe problem of inverse scattering where the scattering structure is unknown, and the physical properties are predicted from the measured echo when the target is insonified with known waveforms, is investigated in this thesis. The scattering structure studied is a submerged, evacuated, spherical elastic shell. The formulation of the echo is carried out using thin shell theory for low and middle frequency range, which basically assumes that shear stresses are negligible. The echo is characterized by the form function in the frequency domain, and the impulse response in the time domain. The results of this thesis show that when using a chirp signal with a 200-250kHz bandwidth as the incident waveform, both the material and size of the shell can be recovered. However, the exact thickness of the shell wall couldn't be extracted.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15423
- Subject Headings
- Elastic plates and shells, Sonar, Frequency response (Dynamics)
- Format
- Document (PDF)
- Title
- A mid-frequency vibration analysis of a T-beam.
- 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 mid-frequency 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 mid-frequency 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 beams--Vibration, Finite element methods, Monte Carlo method
- Format
- Document (PDF)
- Title
- A three-dimensional forward-look sonar simulation model.
- Creator
- Gazagnaire, Julia., Florida Atlantic University, Cuschieri, Joseph M., Beaujean, Pierre-Philippe
- Abstract/Description
-
The aim of this thesis is to develop a simulation tool, The 3-D Forward-Look Sonar Simulation Model (3-D-FLSSM), for the 3-D Forward Look Sonar or equivalent that provides insight to the defining characteristics of the sonar system that affect the image quality and the data processing. The simulator includes a representation of the acoustic environment, which incorporates a flat seafloor and spherical target, both of which are assumed to a have small-scale roughness (much less than the...
Show moreThe aim of this thesis is to develop a simulation tool, The 3-D Forward-Look Sonar Simulation Model (3-D-FLSSM), for the 3-D Forward Look Sonar or equivalent that provides insight to the defining characteristics of the sonar system that affect the image quality and the data processing. The simulator includes a representation of the acoustic environment, which incorporates a flat seafloor and spherical target, both of which are assumed to a have small-scale roughness (much less than the acoustic wavelength) associated with them. The backscatter from the target and the seafloor are calculated using the Rayleigh-Rice approximation implementing Kuo's backscattering cross section. The simulator is capable of modeling targets of various shapes and sizes. The 3-D-FLSSM assumes a plane wave approximation and a constant sound velocity throughout the water column. The final product is a simulation tool with a focus on shallow water littoral acoustics, which can be used to define the sonar hardware and processing software necessary to meet various operational requirements.
Show less - Date Issued
- 2003
- PURL
- http://purl.flvc.org/fcla/dt/13002
- Subject Headings
- Sonar--Computer simulation, Underwater acoustics, Remote submersibles
- Format
- Document (PDF)
- Title
- Influence of the boundaries on the acoustic scattering by a submerged target.
- Creator
- Charmes, Emmanuel., Florida Atlantic University, Beaujean, Pierre-Philippe, Cuschieri, Joseph M.
- Abstract/Description
-
In shallow water or fluid half-space, the acoustic scattering from a target is significantly different from that of an unbounded medium, due to the multiple reflections occurring between the target and the boundaries. The purpose of this thesis is to investigate the influence of the boundaries on the acoustic scattering of a rigid sphere by means of a superposition method. A minimum number of point sources necessary to accurately model the scattered field is determined in the case of a free...
Show moreIn shallow water or fluid half-space, the acoustic scattering from a target is significantly different from that of an unbounded medium, due to the multiple reflections occurring between the target and the boundaries. The purpose of this thesis is to investigate the influence of the boundaries on the acoustic scattering of a rigid sphere by means of a superposition method. A minimum number of point sources necessary to accurately model the scattered field is determined in the case of a free medium, a fluid half-space and a waveguide. The free field symmetry vanishes due to the presence of boundaries and, at particular frequencies or scatterer depths, a significant change in the magnitude and spatial distribution of the scattered field occur. In an unbounded medium or fluid half space, the superposition method is shown to give similar results to analytical formulations found in the literature, provided enough point sources are used.
Show less - Date Issued
- 2005
- PURL
- http://purl.flvc.org/fcla/dt/13211
- Subject Headings
- Electromagnetic waves--Scattering, Acoustical engineering, Sound-waves--Measurement, Wave-motion, Theory of
- Format
- Document (PDF)
- Title
- Tire noise resulting from open grid bridge decks.
- Creator
- Gregory, Scott Andrew., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
When a vehicle crosses the grid section of an open grid bridge deck, a tonal noise is generated. The tonal character of the noise is a consequence of the periodic excitation of both the tire and the grid. The excitation comes from the interaction between the vehicle tire and the periodic grid members. In this thesis, the parameters that control the level and frequency of the generated noise are investigated, with emphasis on quantifying the contribution to the overall noise level of the noise...
Show moreWhen a vehicle crosses the grid section of an open grid bridge deck, a tonal noise is generated. The tonal character of the noise is a consequence of the periodic excitation of both the tire and the grid. The excitation comes from the interaction between the vehicle tire and the periodic grid members. In this thesis, the parameters that control the level and frequency of the generated noise are investigated, with emphasis on quantifying the contribution to the overall noise level of the noise from the tire. The work in this thesis includes both laboratory and field measurements as well as theoretical analysis based on a ring model of the tire. By determining radiated acoustic power from the tires relative to the input force, the sound pressure level radiated from the tires when they cross the open grid deck is estimated. The results of this study show that the tire is the dominant source of noise on open grid bridges and in order to reduce the overall radiated noise, the excitation of the tires by the grid must be reduced. This can be accomplished by either infilling the grid deck or designing the grid to reduce the severity of the periodic excitation force.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/15054
- Subject Headings
- Bridges, Iron and steel--Floors, Bridges, Steel plate deck, Bridges--Noise, Tires--Noise
- Format
- Document (PDF)
- Title
- Estimation of cross range dimensions from a single beam forward look SONAR.
- Creator
- Park, Joseph C., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A computer algorithm is developed to provide real-time cross range spatial quantization for a single beam forward look SONAR similar in operation to a typical sidescan SONAR. This involves the computer simulation of return time signals generated by scanning a surface profile. The time signals are normalized with respect to the scanning altitude to simulate the application of a time varying gain, and then are used as input to the surface estimation algorithm. The algorithm requires two time...
Show moreA computer algorithm is developed to provide real-time cross range spatial quantization for a single beam forward look SONAR similar in operation to a typical sidescan SONAR. This involves the computer simulation of return time signals generated by scanning a surface profile. The time signals are normalized with respect to the scanning altitude to simulate the application of a time varying gain, and then are used as input to the surface estimation algorithm. The algorithm requires two time signals acquired from adjacent scanning positions and solves a stereoscopic geometry in arriving at the surface estimate. Final estimates have an error of less than 1% in target height determination within a set range of operation.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14501
- Subject Headings
- Sonar--Computer simulation, Signal processing--Computer simulation, Underwater acoustics--Computer simulation
- Format
- Document (PDF)
- Title
- Characterization of the acoustic signature of an Ocean Explorer class AUV.
- Creator
- Lambe, Frederic Lionel., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The radiated noise from Autonomous Underwater Vehicles (AUV's) can interfere with on-board sensors and with certain type of missions. It is thus important to understand the parameters controlling the AUV self noise. In this thesis, measurement techniques and analyses are developed to investigate the mechanisms contributing to the acoustic noise of an Ocean Explorer class AUV. Measurements of the AUV acoustic signature are performed in a reverberant tank, after the tank is qualified to...
Show moreThe radiated noise from Autonomous Underwater Vehicles (AUV's) can interfere with on-board sensors and with certain type of missions. It is thus important to understand the parameters controlling the AUV self noise. In this thesis, measurement techniques and analyses are developed to investigate the mechanisms contributing to the acoustic noise of an Ocean Explorer class AUV. Measurements of the AUV acoustic signature are performed in a reverberant tank, after the tank is qualified to establish a reliable procedure to measure the AUV source levels. The measurement results are compared that obtained in an anechoic tank and in open-water. Acoustic measurements are correlated with vibration measurements performed on various components of the AUV, in order to identify the dominant components. From the results, some preliminary mitigation procedures to reduce the AUV acoustic signature are developed.
Show less - Date Issued
- 1999
- PURL
- http://purl.flvc.org/fcla/dt/15618
- Subject Headings
- Oceanographic submersibles, Underwater acoustics
- Format
- Document (PDF)