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- Title
- Correctness analysis of cache conherence protocols using Petri nets.
- Creator
- Hassan, Ahmed Kamal., Florida Atlantic University, Mahgoub, Imad
- Abstract/Description
-
The use of cache memories in multiprocessor systems increases the overall systems performance. Caches reduce the amount of network traffic and provide a solution to the memory contention problem. However, caches introduce memory consistency problems. The existence of multiple cache copies of a memory block will result in an inconsistent view of memory if one processor changes a value in its associated cache. Cache coherence protocols are algorithms designed in software or hardware to maintain...
Show moreThe use of cache memories in multiprocessor systems increases the overall systems performance. Caches reduce the amount of network traffic and provide a solution to the memory contention problem. However, caches introduce memory consistency problems. The existence of multiple cache copies of a memory block will result in an inconsistent view of memory if one processor changes a value in its associated cache. Cache coherence protocols are algorithms designed in software or hardware to maintain memory consistency. With the increased complexity of some of the more recent protocols, testing for the correctness of these protocols becomes an issue that requires more elaborate work. In this thesis, correctness analysis of a selected group of representative cache coherence protocols was performed using Petri nets as a modeling and analysis tool. First, the Petri net graphs for these protocols were designed. These graphs were built by following the logical and coherence actions performed by the protocols in response to the different processors' requests that threatens memory consistency. Correctness analysis was then performed on these graphs.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15366
- Subject Headings
- Cache memory, Multiprocessors, Computer network protocols, Petri nets
- Format
- Document (PDF)
- Title
- The role of polyethylene duct cracking in the failure of post-tensioned cables in Florida segmental bridges.
- Creator
- David, Florent Martin., Florida Atlantic University, Hartt, William H.
- Abstract/Description
-
During the past several decades, segmental construction using precast sections has evolved as a preferred design and construction method for bridges. The tendons used to hold the precast sections together are comprised of cables surrounded by a plastic duct filled with grout. Cracking of the tendon's protective plastic duct has been observed in several Florida bridges. An experimental investigation was performed to characterize the material properties of the high density polyethylene ducts...
Show moreDuring the past several decades, segmental construction using precast sections has evolved as a preferred design and construction method for bridges. The tendons used to hold the precast sections together are comprised of cables surrounded by a plastic duct filled with grout. Cracking of the tendon's protective plastic duct has been observed in several Florida bridges. An experimental investigation was performed to characterize the material properties of the high density polyethylene ducts used in the past and those being specified nowadays. The degree of cure of the resin, the results of three-point bending tests for unnotched and notched specimens, the coefficient of thermal expansion, and the deformation of a tendon as a function of temperature changes were studied. The effects of the grouting pressure and the void presence in the grout were quantified and the pressurization period was shown to affect significantly the pipe strain.
Show less - Date Issued
- 2003
- PURL
- http://purl.flvc.org/fcla/dt/12999
- Subject Headings
- Pipe, Plastic--Testing, Bridges--Florida, Post-tensioned prestressed concrete construction
- Format
- Document (PDF)
- Title
- An ultrareliable multicomputer architecture for real time control applications.
- Creator
- Buechler, Peter Charles., Florida Atlantic University, Fernandez, Eduardo B.
- Abstract/Description
-
This thesis considers the design of ultrareliable multicomputers for control applications. The fault tolerance problem is divided into three subproblems: software, processing node, and communication fault tolerance. Design is performed using layers of abstraction, with fault tolerance implemented by dedicated layers. For software fault tolerance, new constructs for concurrent n-version programming are introduced. For processing node fault tolerance, the distributed fault tolerance (DFT)...
Show moreThis thesis considers the design of ultrareliable multicomputers for control applications. The fault tolerance problem is divided into three subproblems: software, processing node, and communication fault tolerance. Design is performed using layers of abstraction, with fault tolerance implemented by dedicated layers. For software fault tolerance, new constructs for concurrent n-version programming are introduced. For processing node fault tolerance, the distributed fault tolerance (DFT) concept of Chen and Chen is extended to allow for arbitrary failures. Communication fault tolerance is achieved with multicasting on a fault-tolerant graph (FG) network. Reliability models are developed for each of the layers, and a performance model is developed for the communication layer. An example flight control system is compared to currently existing architectures.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14573
- Subject Headings
- Computers--Reliability, Fault-tolerant computing, Real-time data processing, Flight control
- 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 new architecture for interconnection of broadband LANs.
- Creator
- Chao, Jesus., Florida Atlantic University, Chao, Ching-Yun
- Abstract/Description
-
A new topology is proposed that is regular in structure and allows broadband Local Area Networks to be connected together to support a large number of users. The topology is based on connecting local area networks in cube fashion and allows for systematic growth as the need arises. These cubes are attached to each other as building blocks by adding cubes evenly in all three dimensions. In an operational network, irregularities occur due to failures at gateways. An addressing scheme and an...
Show moreA new topology is proposed that is regular in structure and allows broadband Local Area Networks to be connected together to support a large number of users. The topology is based on connecting local area networks in cube fashion and allows for systematic growth as the need arises. These cubes are attached to each other as building blocks by adding cubes evenly in all three dimensions. In an operational network, irregularities occur due to failures at gateways. An addressing scheme and an automatic routing algorithm are developed that makes it possible to add new users without affecting the addresses of existing nodes. The capacity of the proposed networking architecture is determined and compares favorably to that of hypercube interconnected LANs when the number of rings in the network is small.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14564
- Subject Headings
- Local area networks (Computer networks), Broadband communication systems
- Format
- Document (PDF)
- Title
- A methodology for object-oriented modeling and design of real-time, fault-tolerant systems.
- Creator
- Hancock, Debera R., Florida Atlantic University, Fernandez, Eduardo B.
- Abstract/Description
-
Many methodologies for software modeling and design include some form of static and dynamic modeling to describe the structural and behavioral views respectively. Modeling and design of complex real-time software systems requires notations for describing concurrency, asynchronous event handling, communication between independent machines, timing properties, and accessing real time. Function-oriented structured analysis methodologies such as Ward and Mellor's SA/RT and Harel's Statecharts have...
Show moreMany methodologies for software modeling and design include some form of static and dynamic modeling to describe the structural and behavioral views respectively. Modeling and design of complex real-time software systems requires notations for describing concurrency, asynchronous event handling, communication between independent machines, timing properties, and accessing real time. Function-oriented structured analysis methodologies such as Ward and Mellor's SA/RT and Harel's Statecharts have provided extensions for real-time system modeling. Dynamic modeling of real time systems using object-oriented methodologies also requires extensions to the traditional state machine notations in order to convey the real time system characteristics and constraints. Shaw's Communicating Real Time State Machines (CRSM's), Harel's O-Chart notations, and the Octopus methodology provide methods for modeling real-time systems consistent with object-oriented methods. This thesis proposes an object-oriented analysis and design methodology that augments the traditional Object Modeling Technique (OMT) dynamic model with real-time extensions based on high-level parallel machines and communication notations from CRSM. An example of the proposed methodology is provided using a realistic but hypothetical example of an automated passenger train system. A design refinement step is included for fault tolerant considerations. An evaluation of the proposed methodology with its extended notations is provided.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15405
- Subject Headings
- Object-oriented methods (Computer science), Fault-tolerant computing, Real-time programming
- Format
- Document (PDF)
- Title
- The normal incidence reflection coefficient of a sandy seabed as a function of frequency.
- Creator
- Arizzi, Ernest Allen., Florida Atlantic University, Schock, Steven G.
- Abstract/Description
-
A thesis investigates the measured and theoretical pressure reflection coefficients of the seabed at normal incidence. The theoretical reflection coefficient is calculated using a physics-based model developed by Maurice Biot. The model describes sound propagation in saturated porous media and interrelationships between the acoustic properties of the media and the physical properties of the pore fluid and the porous solid. Stoll modified the Biot model for the case of ocean sediments and...
Show moreA thesis investigates the measured and theoretical pressure reflection coefficients of the seabed at normal incidence. The theoretical reflection coefficient is calculated using a physics-based model developed by Maurice Biot. The model describes sound propagation in saturated porous media and interrelationships between the acoustic properties of the media and the physical properties of the pore fluid and the porous solid. Stoll modified the Biot model for the case of ocean sediments and developed an expression for calculating the reflection coefficient as a function of frequency. This thesis tests the model by comparing the reflection coefficient measured with chirp sonar to the reflection coefficient calculated using the Biot model. An experiment was conducted off Fort Walton Beach, Florida where chirp sonar transmitted FM pulses at normal incidence to a sandy seabed. Sediment properties measured during SAX-99 are used to calculate the theoretical reflection coefficient using the Biot-Stoll model. The agreement of the measured reflection coefficients with the theoretical calculations over the band of 1500 to 16000 Hz varies as much as 70%. The plotted results show a reduction of the reflection coefficient with frequency but the large deviations from the trend prevent any further conclusions.
Show less - Date Issued
- 2004
- PURL
- http://purl.flvc.org/fcla/dt/13191
- Subject Headings
- Marine sediments--Acoustic properties, Underwater acoustics--Measurement, Sedimentation analysis
- Format
- Document (PDF)
- Title
- A second order leaky bucket algorithm for traffic shaping in ATM networks.
- Creator
- Bansal, Atul., Florida Atlantic University, Ilyas, Mohammad
- Abstract/Description
-
Asynchronous Transfer Mode (ATM) Networks are based on connections that are multiplexed dynamically on a single link. For satisfactory performance in an ATM network, congestion control is extremely necessary to guarantee the negotiated Quality of Service (QoS) for every connection. Traffic shaping is a congestion control mechanism that alters the traffic characteristics of a stream of cells on a connection to achieve better network efficiency by meeting the QoS objectives. We study a model...
Show moreAsynchronous Transfer Mode (ATM) Networks are based on connections that are multiplexed dynamically on a single link. For satisfactory performance in an ATM network, congestion control is extremely necessary to guarantee the negotiated Quality of Service (QoS) for every connection. Traffic shaping is a congestion control mechanism that alters the traffic characteristics of a stream of cells on a connection to achieve better network efficiency by meeting the QoS objectives. We study a model for Traffic Shaping, Second Order Leaky Bucket, which consists of two leaky buckets to police the Sustained Cell Rate (SCR) and Burst Tolerance (BT) for each ATM connection. With this algorithm, ATM cells enter the first leaky bucket and the Cells conforming to the first leaky bucket enter the ATM network with Cell Loss Priority set to zero (CLP = 0). Any cell non-conforming to the first leaky bucket is sent to a second leaky bucket, and will be tagged CLP = 1 only if found to be non-conforming to the second leaky bucket. Cells conforming to the second leaky bucket are allowed to enter the ATM network with CLP = 0. We simulate the second-order leaky bucket for traffic shaping and show the effectiveness of second order leaky bucket in protecting the QoS experienced by connections passing through a common internodal link queue.
Show less - Date Issued
- 1998
- PURL
- http://purl.flvc.org/fcla/dt/15607
- Subject Headings
- Asynchronous transfer mode, Telecommunication--Traffic, Computer networks
- Format
- Document (PDF)
- Title
- A software-hardware implementation of a real-time digital signal processing receiver for noise detection using a broadband microwave correlation technique.
- Creator
- Christodoulou, Christodoulos A., Florida Atlantic University, Helmken, Henry
- Abstract/Description
-
In this research project the objective is to realize a software - hardware design implementation of a real time digital signal processing (DSP) radiometer - receiver for atmospheric noise temperature detection using the digital cross correlation technique. Atmospheric noise in the band of 20-30 GHz band is down-converted to 10.7 MHz IF and 3 MHz bandwidth in the form of statistical additive white gaussian noise which is used as the received signal by a digital signal processing broadband...
Show moreIn this research project the objective is to realize a software - hardware design implementation of a real time digital signal processing (DSP) radiometer - receiver for atmospheric noise temperature detection using the digital cross correlation technique. Atmospheric noise in the band of 20-30 GHz band is down-converted to 10.7 MHz IF and 3 MHz bandwidth in the form of statistical additive white gaussian noise which is used as the received signal by a digital signal processing broadband microwave radiometer based on the digital cross correlation technique. Living in a technological era, which is characterized as the era of data transmission and reception for RF-wireless communication systems, the theory of RF digital signal processing detection has applied to radar, ultrasound, and digital communications. Due to the need of high speed of data detection, much effort has gone into the design and development of sophisticated equipment to obtain such DSP detectors. Detection can also apply in seismic and big earthquake measurements by using geophones, nuclear testing, sonar and acoustic localizations, and even for oil excavations. Based on a statistical model and proposed design implementation, a basic DSP atmospheric noise temperature radiometer system is introduced and developed. The realization of the DSP Radiometer examines the noise characteristics (parameters) and their corresponding parameter values at the received input at the Antenna. It is essential to introduce the fundamental and statistical properties of the additive white gaussian noise, as well as the key-parameters which are used for the development of this real time design implementation. A design implementation of the proposed DSP atmospheric noise radiometer is discussed and developed via a statistical analysis. The statistical analysis utilizes the standard deviation, intermediate frequency, bandwidth, number of samples, and the temperature of the noise received signal at the antenna. Measurements and real time simulations in order to evaluate the noise temperature’s detectability in terms of system’s accuracy and performance of the noise random variable are also presented in this research work. The advantage of the digital cross correlation technique is examined and investigated.
Show less - Date Issued
- 2005
- PURL
- http://purl.flvc.org/fcla/dt/13290
- Subject Headings
- Signal processing--Digital techniques, Analog-to-digital converters, Radio--Receivers and reception
- Format
- Document (PDF)
- Title
- A simplified Jacobian representation for robot manipulators.
- Creator
- Alewine, Neal Jon., Florida Atlantic University, Roth, Zvi S.
- Abstract/Description
-
Central to many manipulator positional control schemes is a requirement to invert the forward kinematic equations which model the given manipulator. It is shown in this thesis that for manipulator types where a common wrist center exists, a simplified Jacobian form is feasible and its inversion can be used in place of inverse kinematic solutions for positional control. The Jacobian simplification is obtained by decoupling of the wrist member from the positional member, resulting in a Jacobian...
Show moreCentral to many manipulator positional control schemes is a requirement to invert the forward kinematic equations which model the given manipulator. It is shown in this thesis that for manipulator types where a common wrist center exists, a simplified Jacobian form is feasible and its inversion can be used in place of inverse kinematic solutions for positional control. The Jacobian simplification is obtained by decoupling of the wrist member from the positional member, resulting in a Jacobian inversion involving the solution of two sets of three equations with three unknowns. Within the development of the alternate Jacobian form, a technique for substituting incremental rotations with incremental translations is introduced yielding better insight into the Jacobian structure. A requirement for small moves is validated with a discussion of a proposed positional control strategy and a comprehensive example is presented as a summary of the results.
Show less - Date Issued
- 1988
- PURL
- http://purl.flvc.org/fcla/dt/14477
- Subject Headings
- Robots, Manipulators (Mechanism), Matrices
- Format
- Document (PDF)
- Title
- A simulation study of mobile computing protocols.
- Creator
- Ahson, Syed Alamdar., Florida Atlantic University, Ilyas, Mohammad
- Abstract/Description
-
With the advent of cellular technology and portable computers we are on the verge of a new computing paradigm. This computing paradigm is now widely known as "mobile" or "nomadic" computing. Mobile systems frequently change their point of attachment to the network. Mobile computing systems also need to communicate with the existing pool of information and file servers. Mobility defies the very principles that the TCP/IP protocol suite is based on. We study the Internet Engineering Task Force ...
Show moreWith the advent of cellular technology and portable computers we are on the verge of a new computing paradigm. This computing paradigm is now widely known as "mobile" or "nomadic" computing. Mobile systems frequently change their point of attachment to the network. Mobile computing systems also need to communicate with the existing pool of information and file servers. Mobility defies the very principles that the TCP/IP protocol suite is based on. We study the Internet Engineering Task Force (IETF) Mobile IPv4 protocol and find it to be a highly scale solution. We study some of the other proposed mobile IP solutions. We establish a criterion, call-to-mobility ratio, to compare various mobile IP schemes. Two hypothetical schemes, Static Update and Triangular Routing, are introduced solely for the purpose of comparing the performance of Mobile IPv4. In our simulation we concentrate on calculating the update costs and the routing costs for Triangular Routing, Static update and Mobile IPv4 schemes. The simulation program to simulate Triangular Routing, Static Update and Mobile IPv4 is written in C++. Minetsim, our simulation program is written using object-oriented analysis and design. Minetsim is used to obtain routing and update costs for Triangular Routing, Static Update and Mobile IPv4 schemes. Four different host configurations are simulated for travelling salesman and random motion mobility models.
Show less - Date Issued
- 1998
- PURL
- http://purl.flvc.org/fcla/dt/15567
- Subject Headings
- Mobile computing, Portable computers, Internetworking (Telecommunication)
- 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
- A reduced overhead routing protocol for ad hoc wireless networks.
- Creator
- Ibriq, Jamil, Florida Atlantic University, Wu, Jie
- Abstract/Description
-
This document describes the Reduced Overhead Routing (ROR) protocol for use in mobile wireless ad hoc networks. The protocol is highly bandwidth-efficient. The protocol has three distinguishing features: First, it maintains, for each destination, multiple paths. Second, routing table updates are localized. Updates are initiated only when the update table is not empty and the update frequency has not exceeded a specified rate. Third, ROR uses threshold routing technique; it allows an...
Show moreThis document describes the Reduced Overhead Routing (ROR) protocol for use in mobile wireless ad hoc networks. The protocol is highly bandwidth-efficient. The protocol has three distinguishing features: First, it maintains, for each destination, multiple paths. Second, routing table updates are localized. Updates are initiated only when the update table is not empty and the update frequency has not exceeded a specified rate. Third, ROR uses threshold routing technique; it allows an intermediate node to deliver data packet via a longer sub-optimal route that is within the distance. To prevent frequent updates, at most one update is initiated every predefined period of time. A node transmits each update with propagation radius that is determined on the basis of node's network region using a novel probabilistic technique. Threshold routing and localized probabilistic updates greatly reduce routing overhead and network congestion and improve bandwidth efficiency.
Show less - Date Issued
- 2000
- PURL
- http://purl.flvc.org/fcla/dt/12703
- Subject Headings
- Mobile computing, Computer networks, Wireless communication systems
- Format
- Document (PDF)
- Title
- A post-processing Kalman smoother for underwater vehicle navigation.
- Creator
- Gustafson, Einar Irgens., Florida Atlantic University, An, Edgar
- Abstract/Description
-
This thesis describes an automated post-processing tool, designed for use on navigational data gathered by Autonomous Underwater Vehicles (AUVs), developed and operated by the Department of Ocean Engineering at Florida Atlantic University. The post-processing tool consists of a 9-state complementary Kalman filter in conjunction with a Rauch-Tung-Striebel (RTS) smoothing algorithm. The Kalman filter is run forward in time to merge navigational data from an Inertial Measurement Unit (IMU), a...
Show moreThis thesis describes an automated post-processing tool, designed for use on navigational data gathered by Autonomous Underwater Vehicles (AUVs), developed and operated by the Department of Ocean Engineering at Florida Atlantic University. The post-processing tool consists of a 9-state complementary Kalman filter in conjunction with a Rauch-Tung-Striebel (RTS) smoothing algorithm. The Kalman filter is run forward in time to merge navigational data from an Inertial Measurement Unit (IMU), a Doppler Velocity Log (DVL), a magnetic compass, a GPS/DGPS system and an Ultrashort Baseline (USBL) tracking system. Subsequently, the RTS smoothing algorithm is run backwards in time to find and compensate for drift errors in dead reckoned position and compass measurement error. The post-processing tool has been implemented as a graphical user interface, designed in MATLAB. Improved accuracy in post-processed position and heading has been verified by conducting sea trials and post-processing the collected data.
Show less - Date Issued
- 2001
- PURL
- http://purl.flvc.org/fcla/dt/12752
- Subject Headings
- Kalman filtering, Underwater navigation
- Format
- Document (PDF)
- Title
- A passive platform for tracking underwater vehicles.
- Creator
- Dufour, Emmanuel R., Florida Atlantic University, Glegg, Stewart A. L.
- Abstract/Description
-
Over recent years, the trend in Autonomous Underwater Vehicle (AUV) design has been to reduce vehicle size and cost. On board navigation systems are both large and expensive so alternate solutions for vehicle positioning are required. The thesis explores the performance of a passive platform, the Ambient Noise Sonar (ANS), in remotely detecting, localizing and tracking submersible vessels. This task is achieved by exploiting communication signatures emitted by the moving submersible. The...
Show moreOver recent years, the trend in Autonomous Underwater Vehicle (AUV) design has been to reduce vehicle size and cost. On board navigation systems are both large and expensive so alternate solutions for vehicle positioning are required. The thesis explores the performance of a passive platform, the Ambient Noise Sonar (ANS), in remotely detecting, localizing and tracking submersible vessels. This task is achieved by exploiting communication signatures emitted by the moving submersible. The utility modem integrated on the AUV can be operated in a PSK and a MFSK mode. It was demonstrated that the ANS successfully tracks AUVs in both cases. First, the thesis presents the sonar beamformer and shows its potential for tracking by using the AUV communication signals. It describes a scheme developed to enhance the processor performance in a multi-target configuration and clutter. Then, it discusses promising tracking results from experiments conducted in summer and fall 1998, off the coast of South Florida.
Show less - Date Issued
- 1999
- PURL
- http://purl.flvc.org/fcla/dt/15671
- Subject Headings
- Oceanographic submersibles--Automatic control, Underwater acoustics, Acoustical engineering
- Format
- Document (PDF)
- Title
- A volume scattering model for sediment classification through acoustic means.
- Creator
- Jenkins, Michael Gerard., Florida Atlantic University, LeBlanc, Lester R.
- Abstract/Description
-
A simple model is developed to evaluate the acoustic scattering environment of sediments based on the envelope function of digital sub-bottom sonar data. Scattering pressure and intensity histograms are produced from model results. These histograms are compared to the theoretical distributions expected for scattering event pressure and intensity. Sediment composition is inferred from the determined acoustic scattering environment. The model has been applied to X-Star digital sub-bottom data...
Show moreA simple model is developed to evaluate the acoustic scattering environment of sediments based on the envelope function of digital sub-bottom sonar data. Scattering pressure and intensity histograms are produced from model results. These histograms are compared to the theoretical distributions expected for scattering event pressure and intensity. Sediment composition is inferred from the determined acoustic scattering environment. The model has been applied to X-Star digital sub-bottom data taken in the vicinity of St. John's Harbor, New Brunswick. Model results are compared to ground truth (Borehole logs) taken within the survey area. This comparison indicates general trends within the sediment scattering environment which may be linked to sediment composition. Distinct differences in model results were noted over areas of differing sediment types.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/14945
- Subject Headings
- Sedimentation analysis, Underwater acoustics, Sound--Reverberation
- Format
- Document (PDF)
- Title
- Electrochemical behavior of carbon fiber cathode materials in organic electrolytes containing various lithium salts.
- Creator
- Durand, Severine Nathalie., Florida Atlantic University, Lipka, Stephen M.
- Abstract/Description
-
The intercalation of anions into carbon fiber from organic electrolytes containing lithium salts was studied. The reversible intercalation of anions into carbon could lead to the possible substitution of conventional metal oxide cathode materials in lithium-ion cells. EWC300 was selected as the most suitable carbon fiber material based on data from preliminary tests. Experiments were performed with LiClO4 in EC/DMC and LiPF6 in EC/DMC electrolytes. Slow scan cyclic voltammetry (0.1 mV/s) and...
Show moreThe intercalation of anions into carbon fiber from organic electrolytes containing lithium salts was studied. The reversible intercalation of anions into carbon could lead to the possible substitution of conventional metal oxide cathode materials in lithium-ion cells. EWC300 was selected as the most suitable carbon fiber material based on data from preliminary tests. Experiments were performed with LiClO4 in EC/DMC and LiPF6 in EC/DMC electrolytes. Slow scan cyclic voltammetry (0.1 mV/s) and galvanostatic charge/discharge experiments at various C rates were used. Intercalation of PF6- occurred by staging and was highly dependent on the current density. High current density (20 mA/g) was necessary to reach potentials over 5 V vs Li to achieve intercalation capacities over 80 mAh/g. Powder x-ray diffraction revealed that carbon fibers became less crystalline after anions were intercalated into their structure. Scanning electron microscopy showed longitudinal cracking on the carbon fibers after 120 cycles indicating dimensional instability.
Show less - Date Issued
- 1999
- PURL
- http://purl.flvc.org/fcla/dt/15624
- Subject Headings
- Anions, Carbon fibers, Lithium cells, Electrochemical analysis
- Format
- Document (PDF)
- Title
- Effect of steel reinforcement type and surface condition on corrosion initiation in mortar.
- Creator
- Huang, Yirong., Florida Atlantic University, Hartt, William H.
- Abstract/Description
-
This study employed half-cell potential (Eoc), polarization resistance (PR) and galvanic current tests to explore effects of surface condition and steel reinforcement type on corrosion initiation in mortar. A low impurity steel plate and #10 grade 60 rebar were used. Four surface conditions (as-received, atmospherically rusted, #240 SiC paper polished, and #500 SiC paper polished) were employed. Cyclic wet and dry exposure of specimens in 15% NaCl solution was conducted. Half-cell potential...
Show moreThis study employed half-cell potential (Eoc), polarization resistance (PR) and galvanic current tests to explore effects of surface condition and steel reinforcement type on corrosion initiation in mortar. A low impurity steel plate and #10 grade 60 rebar were used. Four surface conditions (as-received, atmospherically rusted, #240 SiC paper polished, and #500 SiC paper polished) were employed. Cyclic wet and dry exposure of specimens in 15% NaCl solution was conducted. Half-cell potential measurements showed that the corrosion probability of specimens with as-received and pre-rusted surfaces was lower than that of specimens with a polished surface. However, the PR and galvanic current tests indicated higher corrosion rate for specimens prepared with atmospherically rusted and as-received steels. Good agreement was found between results of the polarization resistance test and galvanic current measurements. There is a lack of correlation between half-cell potential and corrosion rate.
Show less - Date Issued
- 2003
- PURL
- http://purl.flvc.org/fcla/dt/13075
- Subject Headings
- Corrosion and anti-corrosives--Testing, Reinforced concrete--Corrosion, Mortar, Steel--Corrosion
- Format
- Document (PDF)
- Title
- Group structures in object-oriented database authorization.
- Creator
- Fernandez, Minjie Hua., Florida Atlantic University, Wu, Jie
- Abstract/Description
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When there are a large number and a variety of users in a system, the authorization rules for these users will become too difficult and cumbersome to maintain and the evaluation algorithm would not be efficient. Also, it is hard for security administrators to understand why a specific user is given a set of rights. In this thesis we develop group structures to solve these problems. Groups of users rather than individual users are subjects that receive access rights from the authorization...
Show moreWhen there are a large number and a variety of users in a system, the authorization rules for these users will become too difficult and cumbersome to maintain and the evaluation algorithm would not be efficient. Also, it is hard for security administrators to understand why a specific user is given a set of rights. In this thesis we develop group structures to solve these problems. Groups of users rather than individual users are subjects that receive access rights from the authorization system. We present structurings and primitives for user groups. Although they are presented in the context of an object-oriented database system they are general and could be applied to other data model, and even in operating systems.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/14878
- Subject Headings
- Electronic data processing--Security measures, User interfaces (Computer systems)
- Format
- Document (PDF)
- Title
- Glass electrodes as a sensor for pH of porewater in concrete.
- Creator
- Balamuralikrishna, Radhakrishnan., Florida Atlantic University, Hartt, William H.
- Abstract/Description
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Experiments were developed and performed to determine if glass electrodes can be employed to accurately measure pH of porewater in concrete. An attempt was made to determine the reason for the general underestimation of the alkalinity of porewater by one or more pH units when glass electrodes are used as sensors compared to the OH- concentration obtained from titration of pore solutions expressed from hydrated cement samples. The linear response and alkaline error of glass electrodes was...
Show moreExperiments were developed and performed to determine if glass electrodes can be employed to accurately measure pH of porewater in concrete. An attempt was made to determine the reason for the general underestimation of the alkalinity of porewater by one or more pH units when glass electrodes are used as sensors compared to the OH- concentration obtained from titration of pore solutions expressed from hydrated cement samples. The linear response and alkaline error of glass electrodes was investigated. pH was measured for mortar samples cast in air as well as under CO2-free conditions. A flat-surface combination electrode was mostly employed for this purpose, but studies also involved the use of a microelectrode. The possible role played by Ca(OH)2 liberated during cement hydration in decarbonation of porewater is discussed based on experiments.
Show less - Date Issued
- 1990
- PURL
- http://purl.flvc.org/fcla/dt/14649
- Subject Headings
- Steel--Corrosion, Concrete--Chemistry
- Format
- Document (PDF)
