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- Title
- MACHINE LEARNING ALGORITHMS FOR THE DETECTION AND ANALYSIS OF WEB ATTACKS.
- Creator
- Zuech, Richard, Khoshgoftaar, Taghi M., Florida Atlantic University, Department of Computer and Electrical Engineering and Computer Science, College of Engineering and Computer Science
- Abstract/Description
-
The Internet has provided humanity with many great benefits, but it has also introduced new risks and dangers. E-commerce and other web portals have become large industries with big data. Criminals and other bad actors constantly seek to exploit these web properties through web attacks. Being able to properly detect these web attacks is a crucial component in the overall cybersecurity landscape. Machine learning is one tool that can assist in detecting web attacks. However, properly using...
Show moreThe Internet has provided humanity with many great benefits, but it has also introduced new risks and dangers. E-commerce and other web portals have become large industries with big data. Criminals and other bad actors constantly seek to exploit these web properties through web attacks. Being able to properly detect these web attacks is a crucial component in the overall cybersecurity landscape. Machine learning is one tool that can assist in detecting web attacks. However, properly using machine learning to detect web attacks does not come without its challenges. Classification algorithms can have difficulty with severe levels of class imbalance. Class imbalance occurs when one class label disproportionately outnumbers another class label. For example, in cybersecurity, it is common for the negative (normal) label to severely outnumber the positive (attack) label. Another difficulty encountered in machine learning is models can be complex, thus making it difficult for even subject matter experts to truly understand a model’s detection process. Moreover, it is important for practitioners to determine which input features to include or exclude in their models for optimal detection performance. This dissertation studies machine learning algorithms in detecting web attacks with big data. Severe class imbalance is a common problem in cybersecurity, and mainstream machine learning research does not sufficiently consider this with web attacks. Our research first investigates the problems associated with severe class imbalance and rarity. Rarity is an extreme form of class imbalance where the positive class suffers extremely low positive class count, thus making it difficult for the classifiers to discriminate. In reducing imbalance, we demonstrate random undersampling can effectively mitigate the class imbalance and rarity problems associated with web attacks. Furthermore, our research introduces a novel feature popularity technique which produces easier to understand models by only including the fewer, most popular features. Feature popularity granted us new insights into the web attack detection process, even though we had already intensely studied it. Even so, we proceed cautiously in selecting the best input features, as we determined that the “most important” Destination Port feature might be contaminated by lopsided traffic distributions.
Show less - Date Issued
- 2021
- PURL
- http://purl.flvc.org/fau/fd/FA00013823
- Subject Headings
- Machine learning, Computer security, Algorithms, Cybersecurity
- Format
- Document (PDF)
- Title
- Context-based Image Concept Detection and Annotation.
- Creator
- Zolghadr, Esfandiar, Furht, Borko, Florida Atlantic University, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
-
Scene understanding attempts to produce a textual description of visible and latent concepts in an image to describe the real meaning of the scene. Concepts are either objects, events or relations depicted in an image. To recognize concepts, the decision of object detection algorithm must be further enhanced from visual similarity to semantical compatibility. Semantically relevant concepts convey the most consistent meaning of the scene. Object detectors analyze visual properties (e.g., pixel...
Show moreScene understanding attempts to produce a textual description of visible and latent concepts in an image to describe the real meaning of the scene. Concepts are either objects, events or relations depicted in an image. To recognize concepts, the decision of object detection algorithm must be further enhanced from visual similarity to semantical compatibility. Semantically relevant concepts convey the most consistent meaning of the scene. Object detectors analyze visual properties (e.g., pixel intensities, texture, color gradient) of sub-regions of an image to identify objects. The initially assigned objects names must be further examined to ensure they are compatible with each other and the scene. By enforcing inter-object dependencies (e.g., co-occurrence, spatial and semantical priors) and object to scene constraints as background information, a concept classifier predicts the most semantically consistent set of names for discovered objects. The additional background information that describes concepts is called context. In this dissertation, a framework for building context-based concept detection is presented that uses a combination of multiple contextual relationships to refine the result of underlying feature-based object detectors to produce most semantically compatible concepts. In addition to the lack of ability to capture semantical dependencies, object detectors suffer from high dimensionality of feature space that impairs them. Variances in the image (i.e., quality, pose, articulation, illumination, and occlusion) can also result in low-quality visual features that impact the accuracy of detected concepts. The object detectors used to build context-based framework experiments in this study are based on the state-of-the-art generative and discriminative graphical models. The relationships between model variables can be easily described using graphical models and the dependencies and precisely characterized using these representations. The generative context-based implementations are extensions of Latent Dirichlet Allocation, a leading topic modeling approach that is very effective in reduction of the dimensionality of the data. The discriminative contextbased approach extends Conditional Random Fields which allows efficient and precise construction of model by specifying and including only cases that are related and influence it. The dataset used for training and evaluation is MIT SUN397. The result of the experiments shows overall 15% increase in accuracy in annotation and 31% improvement in semantical saliency of the annotated concepts.
Show less - Date Issued
- 2016
- PURL
- http://purl.flvc.org/fau/fd/FA00004745, http://purl.flvc.org/fau/fd/FA00004745
- Subject Headings
- Computer vision--Mathematical models., Pattern recognition systems., Information visualization., Natural language processing (Computer science), Multimodal user interfaces (Computer systems), Latent structure analysis., Expert systems (Computer science)
- Format
- Document (PDF)
- Title
- Application of wavelets to image and video coding.
- Creator
- Zolghadr, Esfandiar, Florida Atlantic University, Furht, Borko, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
-
In this thesis we applied wavelet transforms to image and video coding. First, a survey of various wavelets and their features is presented, including continuous, discrete, and orthogonal wavelets. Theories and concepts underlying one and two-dimensional wavelet transforms are introduced and compared to Fourier transform and sub-band coding. The core of the thesis is the implementation of two-dimensional and three-dimensional codec architectures and their application to coding images and...
Show moreIn this thesis we applied wavelet transforms to image and video coding. First, a survey of various wavelets and their features is presented, including continuous, discrete, and orthogonal wavelets. Theories and concepts underlying one and two-dimensional wavelet transforms are introduced and compared to Fourier transform and sub-band coding. The core of the thesis is the implementation of two-dimensional and three-dimensional codec architectures and their application to coding images and videos, respectively. We studied performance of the wavelet codec by comparing it to DCT and JPEG coding techniques. We applied these techniques for compression of a variety of test images and videos. We also analyzed the adaptability and scalability of 2D and 3D codec. Experimental results, presented in the thesis, illustrate the superior performance of wavelets compared to other coding techniques.
Show less - Date Issued
- 2003
- PURL
- http://purl.flvc.org/fcla/dt/13050
- Subject Headings
- Wavelets (Mathematics), Image compression, JPEG (Image coding standard)
- Format
- Document (PDF)
- Title
- Simulation, control and optimization of underwater vehicle performance.
- Creator
- Zipf, David Glenn., Florida Atlantic University, Dunn, Stanley E., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This project addresses the simulation, control and optimization of underwater vehicle performance. An analytical model of underwater vehicle motion has been developed. This model is based on a set of six degree of freedom nonlinear differential equations of motion. These equations incorporate inertial, hydrodynamic, hydrostatic, gravity and thruster forces to define the vehicle's motion. The forces are calculated and the equations of motion solved using a finite difference method of...
Show moreThis project addresses the simulation, control and optimization of underwater vehicle performance. An analytical model of underwater vehicle motion has been developed. This model is based on a set of six degree of freedom nonlinear differential equations of motion. These equations incorporate inertial, hydrodynamic, hydrostatic, gravity and thruster forces to define the vehicle's motion. The forces are calculated and the equations of motion solved using a finite difference method of integration. An automatic closed loop control strategy has been developed and integrated into the motion model. The controller determines control plane deflection and thruster output based on sensor provided input, maneuver request and control gain constants. The motion model simulates the effects of these controller requests on the vehicle motion. The controller effects are analyzed and an optimal set of control gains is determined. These optimal gains are determined based on a quantitative comparison of a pre-defined Performance Index (PI) function. The PI is a function of critical performance values, i.e., energy consumption, and user defined weighted constants. By employing an iteration technique the PI is minimized to provide an optimal set of control gains.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14534
- Subject Headings
- Oceanographic submersibles--Automatic control, Oceanographic submersibles--Simulation methods, Vehicles, Remotely piloted
- Format
- Document (PDF)
- Title
- Application of MoM: Scattering calculations using condition number.
- Creator
- Zhuang, Zhijun., Florida Atlantic University, Bagby, Jonathan S., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
-
Computational accuracy is widely recognized as a critical issue in applied electromagnetics. Increasing computational power is being applied to solve more complex electromagnetic systems with an emphasis on computational accuracy. The work of this thesis is focused on the implementation of Method of Moments (MoM) to integral equation formulations. The goal of this effort is to use what is known as condition number, and, a heuristic rule-of-thumb is applied to investigate the computational...
Show moreComputational accuracy is widely recognized as a critical issue in applied electromagnetics. Increasing computational power is being applied to solve more complex electromagnetic systems with an emphasis on computational accuracy. The work of this thesis is focused on the implementation of Method of Moments (MoM) to integral equation formulations. The goal of this effort is to use what is known as condition number, and, a heuristic rule-of-thumb is applied to investigate the computational accuracy of MoM in numerical electromagnetics. Other possible applications of condition number of the MoM matrix are also indicated.
Show less - Date Issued
- 1999
- PURL
- http://purl.flvc.org/fcla/dt/15719
- Subject Headings
- Electromagnetism, Moments method (Statistics), Electromagnetic theory, Integral equations--Numerical solutions
- Format
- Document (PDF)
- Title
- Feasibility of using carbon fiber reinforced plastic tendons in prestressed concrete Double-Tee bridge system.
- Creator
- Zhuang, Ming., Florida Atlantic University, Arockiasamy, Madasamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
One of the major problems the construction industry faces today is corrosion of reinforcing and prestressing steel, which significantly affects the durability of concrete structures. Fiber reinforced plastics (FRPs) are highly regarded as prospective replacement for steel in prestressed concrete structures under corrosive environment. This investigation was conducted to establish the feasibility of using Carbon Fiber Composite (CFC) cables as reinforcing/prestressing elements in concrete...
Show moreOne of the major problems the construction industry faces today is corrosion of reinforcing and prestressing steel, which significantly affects the durability of concrete structures. Fiber reinforced plastics (FRPs) are highly regarded as prospective replacement for steel in prestressed concrete structures under corrosive environment. This investigation was conducted to establish the feasibility of using Carbon Fiber Composite (CFC) cables as reinforcing/prestressing elements in concrete bridge structures. Besides investigating durability of CFC cables and pretensioned concrete beams with CFC cables in adverse environments (alkali and seawater), flexure and shear tests were performed on single Double-Tee beams, together with service load behavior, fatigue strength and ultimate load capacity tests on a half scale model Double-Tee girder bridge system prestressed with CFC cables. Exposure to seawater and alkali environments has no adverse effect on the strength of the CFRP tendons as well as the pretensioned beams with CFRP. Based on the flexural strength tests on Double-Tee beams, the bond between CFRP tendons and concrete is satisfactory. The Double-Tee bridge system exhibited good fatigue resistance and adequate ductility under ultimate load conditions. The ultimate load capacity of the bridge is approximately three times the service load corresponding to two HS20-44 trucks and equals 2.4 times the first crack load. Finite element analyses were carried out to predict elastic deformations and collapse load of the Double-Tee bridge prestressed with CFC cables. Feasibility of using CFC cables in bridge structures is assessed based on the experimental and analytical parameters such as deflections, strains, crack distributions and crack widths.
Show less - Date Issued
- 1996
- PURL
- http://purl.flvc.org/fcla/dt/12465
- Subject Headings
- Carbon fibers, Composite construction, Fiber reinforced plastics, Bridges, Iron and steel, Reinforced concrete construction, Prestressed concrete construction
- Format
- Document (PDF)
- Title
- NEIGHBORING NEAR MINIMUM-TIME CONTROLS WITH DISCONTINUITIES AND THE APPLICATION TO THE CONTROL OF MANIPULATORS (PATH-PLANNING, TRACKING, FEEDBACK).
- Creator
- Zhuang, Hanqi, Florida Atlantic University, Hamano, Fumio, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
-
This thesis presents several algorithms to treat the problem of closed-loop near minimum-time controls with discontinuities. First, a neighboring control algorithm is developed to solve the problem in which controls are bounded by constant constraints. Secondly, the scheme is extended to account for state-dependent control constraints. And finally, a path tracking algorithm for robotic manipulators is presented, which is also a neighboring control algorithm. These algorithms are suitable for...
Show moreThis thesis presents several algorithms to treat the problem of closed-loop near minimum-time controls with discontinuities. First, a neighboring control algorithm is developed to solve the problem in which controls are bounded by constant constraints. Secondly, the scheme is extended to account for state-dependent control constraints. And finally, a path tracking algorithm for robotic manipulators is presented, which is also a neighboring control algorithm. These algorithms are suitable for real time controls because the on-line computations involved are relatively simple. Simulation results show that these algorithms work well despite the fact that the prescribed final points can not be reached exactly.
Show less - Date Issued
- 1986
- PURL
- http://purl.flvc.org/fcla/dt/14326
- Subject Headings
- Manipulators (Mechanism), Control theory, Algorithms
- Format
- Document (PDF)
- Title
- Kinematic modeling, identification and compensation of robot manipulators.
- Creator
- Zhuang, Hanqi, Florida Atlantic University, Hamano, Fumio, Roth, Zvi S., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
-
Theoretical and practical issues of kinematic modeling, measurement, identification and compensation are addressed in this dissertation. A comprehensive robot calibration methodology using a new Complete and Parametrically Continuous (CPC) kinematic model is presented. The dissertation focuses on model-based robot calibration techniques. Parametric continuity of a kinematic model is defined and discussed to characterize model singularity. Irreducibility is defined to facilitate error model...
Show moreTheoretical and practical issues of kinematic modeling, measurement, identification and compensation are addressed in this dissertation. A comprehensive robot calibration methodology using a new Complete and Parametrically Continuous (CPC) kinematic model is presented. The dissertation focuses on model-based robot calibration techniques. Parametric continuity of a kinematic model is defined and discussed to characterize model singularity. Irreducibility is defined to facilitate error model reduction. Issues of kinematic parameter identification are addressed by utilizing generic forms of linearized kinematic error models. The CPC model is a complete and parametrically continuous kinematic model capable of describing geometry and motion of a robot manipulator. Owing to the completeness of the CPC model, the transformation from the base frame to the world frame and from the tool frame to the last link frame can be modeled with the same modeling convention as the one used for internal link transformations. Due to the parametric continuity of the CPC model, numerical difficulties in kinematic parameter identification using error models are reduced. The CPC model construction, computation of the link parameters from a given link transformation, inverse kinematics, transformations between the CPC model and the Denavit-Hartenberg model, and linearized CPC error model construction are investigated. New methods for self-calibration of a laser tracking coordinate-measuring-machine are reported. Two calibration methods, one based on a four-tracker system and the other based on three trackers with a precision plane, are proposed. Iterative estimation algorithms along with simulation results are presented. Linear quadratic regulator (LQR) theory is applied to design robot accuracy compensators. In the LQR algorithm, additive corrections of joint commands are found without explicitly solving the inverse kinematic problem for an actual robot; a weighting matrix and coefficients in the cost function can be chosen systematically to achieve specific objective such as emphasizing the positioning accuracy of the end-effector over its orientation accuracy and vice versa and taking into account joint travelling limits as well as singularity zones of the robot. The results of the kinematic identification and compensation experiments using the PUMA robot have shown that the CPC modeling technique presented in this dissertation is a convenient and effective means for accuracy improvements of industrial robots.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/12243
- Subject Headings
- Robotics, Manipulators (Mechanism)
- Format
- Document (PDF)
- Title
- Finite element modeling for dislocation generation in semiconductor crystals grown from the melt.
- Creator
- Zhu, Xinai., Florida Atlantic University, Tsai, Chi-Tay, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Dislocations in Gallium Arsenide (GaAs) and Indium Phosphide (InP) single crystals are generated by excessive stresses that are induced during the crystal growth process, and the fabrication and packaging of microelectronic devices/circuits. The presence of dislocations has adverse effects on the performance, lifetime and reliability of the GaAs and InP-based devices/circuits. It is well known that dislocation density can be significantly reduced by doping impurity atoms into the GaAs and InP...
Show moreDislocations in Gallium Arsenide (GaAs) and Indium Phosphide (InP) single crystals are generated by excessive stresses that are induced during the crystal growth process, and the fabrication and packaging of microelectronic devices/circuits. The presence of dislocations has adverse effects on the performance, lifetime and reliability of the GaAs and InP-based devices/circuits. It is well known that dislocation density can be significantly reduced by doping impurity atoms into the GaAs and InP crystal and/or decreasing the thermal stresses in these crystals during their growth process. In order to reduce the dislocation density generated in the GaAs and InP crystals, the influence of crystal growth parameters and doping impurity atoms on the dislocations reduction in GaAs and InP crystals has to be understood. Therefore, a transient finite element model was developed to simulate the dislocation generation in GaAs and InP crystals grown from the melt. A viscoplastic constitutive equation that couples a microscopic dislocation density with a macroscopic plastic deformation is employed to formulate this transient finite element model, where the dislocation density is considered as an internal state variable and the doping impurity is represented by a drag-stress in this constitutive model. GaAs and InP single crystals grown by the vertical gradient freeze (VGF) process were adopted as examples to study the influences of doping impurity and growth parameters on dislocations generated in these grown crystal. The calculated results show that doping impurity can significantly reduce dislocation generation and produces low-dislocation-density or dislocation free GaAs and InP single crystals. It also shows that the dislocations generated in GaAs and InP crystals increase as the crystal diameter and imposed temperature gradient increase, but do not change or increase slightly as the crystal growth rate increases. Therefore, this finite element model can be effectively used by crystal growers to select acceptable levels of doping impurity, crystal diameter, temperature gradient, and growth rate to produce the lowest dislocation density in GaAs and InP crystals through a thorough numerical investigation using this developed finite element model.
Show less - Date Issued
- 2004
- PURL
- http://purl.flvc.org/fcla/dt/12072
- Subject Headings
- Dislocations in crystals, Gallium arsenide semiconductors, Indium phosphide, Metal crystals--Growth
- Format
- Document (PDF)
- Title
- Deterministic, stochastic and convex analyses of one- and two-dimensional periodic structures.
- Creator
- Zhu, Liping., Florida Atlantic University, Lin, Y. K., Elishakoff, Isaac, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The periodic structures considered in the dissertation are one-dimensional periodic multi-span beams, and two-dimensional periodic grillages with elastic interior supports. The following specific topics are included: (1) Deterministic Vibration--Exact solutions are obtained for free vibrations of both multi-span beams and grillages, by utilizing the wave propagation concept. The wave motions at the periodic supports/nodes are investigated and the dispersion equations are derived from which...
Show moreThe periodic structures considered in the dissertation are one-dimensional periodic multi-span beams, and two-dimensional periodic grillages with elastic interior supports. The following specific topics are included: (1) Deterministic Vibration--Exact solutions are obtained for free vibrations of both multi-span beams and grillages, by utilizing the wave propagation concept. The wave motions at the periodic supports/nodes are investigated and the dispersion equations are derived from which the natural frequencies of the periodic structures are determined. The emphasis is placed on the calculation of mode shapes of both types of periodic structures. The general expressions for mode shapes with various boundary conditions are obtained. These mode shapes are used to evaluate the exact dynamic response to a convected harmonic loading. (2) Stochastic Vibration--A multi-span beam under stochastic acoustic loading is considered. The exact analytical expressions for the spectral densities are derived for both displacement and bending moment by using the normal mode approach. Nonlinear vibration of a multi-span beam with axial restraint and initial imperfection are also investigated. In the latter case, the external excitation is idealized as a Gaussian white nose. An expression for the joint probability density function in the generalized coordinates is obtained and used to evaluate the mean square response of a multi-span beam system. (3) Convex Modeling of Uncertain Excitation Field--It is assumed that the parameters of the stochastic excitation field are uncertain and belong to a multi-dimensional convex set. A new approach is developed to determine the multi-dimensional ellipsoidal convex set with a minimum volume. The most and least favorable responses of a multi-span beam are then determined for such a convex set, corresponding to a stochastic acoustic field. The procedure is illustrated in several examples.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/12366
- Subject Headings
- Grillages (Structural engineering), Girders--Vibration, Wave-motion, Theory of, Vibration
- Format
- Document (PDF)
- Title
- Blast/explosion resistant analysis of composite steel girder bridge system.
- Creator
- Zhou, Fang., College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
- Abstract/Description
-
The design of bridge structures to resist explosive loads has become more of a concern to the engineering community. This thesis proposes a method to evaluate the effects of conventional blast loads on a two span continuous composite steel girder bridge system. The bridge design is based on AASHTO LRFD method. Resistance capacities of bridge deck and composite steel girder are calculated according to AASHTO specifications. Equivalent blast pressures on the bridge components are obtained....
Show moreThe design of bridge structures to resist explosive loads has become more of a concern to the engineering community. This thesis proposes a method to evaluate the effects of conventional blast loads on a two span continuous composite steel girder bridge system. The bridge design is based on AASHTO LRFD method. Resistance capacities of bridge deck and composite steel girder are calculated according to AASHTO specifications. Equivalent blast pressures on the bridge components are obtained. Response and performance of concrete deck, steel girders, and supporting piers are evaluated under typical blast loads. The blast induced force in the bridge components are computed in the static analyses for varying amounts of TNT. The blast effects in the supporting pier are determined using both static and dynamic analyses. Further research needs to be done in the dynamic analysis of the bridge system subjected to blast loads.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/227976
- Subject Headings
- Steel, Structural, Testing, Bridges, Design and construction, Structural dynamics
- Format
- Document (PDF)
- Title
- Development of an integrated computational tool for design and analysis of composite turbine blades under ocean current loading.
- Creator
- Zhou, Fang., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A computational tool has been developed by integrating National Renewable Energy Laboratory (NREL) codes, Sandia National Laboratories' NuMAD, and ANSYS to investigate a horizontal axis composite ocean current turbine. The study focused on the design, analysis, and life prediction of composite blade considering random ocean current, cyclic rotation, and hurricane-driven ocean current. A structural model for a horizontal axis FAU research OCT blade was developed. Following NREL codes were used...
Show moreA computational tool has been developed by integrating National Renewable Energy Laboratory (NREL) codes, Sandia National Laboratories' NuMAD, and ANSYS to investigate a horizontal axis composite ocean current turbine. The study focused on the design, analysis, and life prediction of composite blade considering random ocean current, cyclic rotation, and hurricane-driven ocean current. A structural model for a horizontal axis FAU research OCT blade was developed. Following NREL codes were used: PreCom, BModes, ModeShape, AeroDyn and FAST. PreComp was used to compute section properties of the OCT blade. BModes and ModeShape calculated the mode shapes of the blade. Hydrodynamic loading on the OCT blade was calculated by modifying the inputs to AeroDyn and FAST. These codes were then used to obtain the dynamic response of the blade, including blade tip displacement, normal force (FN) and tangential force (FT), flap and edge bending moment distribution with respect to blade rotation.
Show less - Date Issued
- 2013
- PURL
- http://purl.flvc.org/fcla/dt/3362582
- Subject Headings
- Structural dynamics, Fluid dynamics, Marine turbines, Mathematical models, Turbines, Blades, Design and construction
- Format
- Document (PDF)
- Title
- Determination of probability density from statistical moments by neural network approach.
- Creator
- Zheng, Zhiyin., Florida Atlantic University, Cai, Guo-Qiang, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
It is known that response probability densities, although important in failure analysis, are seldom achievable for stochastically excited systems except for linear systems under additive excitations of Gaussian processes. Most often, statistical moments are obtainable analytically or experimentally. It is proposed in this thesis to determine the probability density from the known statistical moments using artificial neural networks. A multi-layered feed-forward type of neural networks with...
Show moreIt is known that response probability densities, although important in failure analysis, are seldom achievable for stochastically excited systems except for linear systems under additive excitations of Gaussian processes. Most often, statistical moments are obtainable analytically or experimentally. It is proposed in this thesis to determine the probability density from the known statistical moments using artificial neural networks. A multi-layered feed-forward type of neural networks with error back-propagation training algorithm is proposed for the purpose and the parametric method is adopted for identifying the probability density function. Three examples are given to illustrate the applicability of the approach. All three examples show that the neural network approach gives quite accurate results in comparison with either the exact or simulation ones.
Show less - Date Issued
- 1996
- PURL
- http://purl.flvc.org/fcla/dt/15330
- Subject Headings
- Distribution (Probability theory), Moments method (Statistics), Estimation theory, Structural failures--Investigation, Neural networks (Computer science)
- Format
- Document (PDF)
- Title
- Modeling and simulation on the yard trailers deployment in the maritime container terminal.
- Creator
- Zhao, Yueqiong, College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
- Abstract/Description
-
In recent years, there has been an exponential increase in container volume shipment within intermodal transportation systems. Container terminals as part of the global port system represent important hubs within this intermodal transportation system. Thus, the need to improve the operational efficiency is the most important issue for container terminals from an economic standpoint. Moreover, intermodal transportation systems, ports and inland transport facilities should all be integrated...
Show moreIn recent years, there has been an exponential increase in container volume shipment within intermodal transportation systems. Container terminals as part of the global port system represent important hubs within this intermodal transportation system. Thus, the need to improve the operational efficiency is the most important issue for container terminals from an economic standpoint. Moreover, intermodal transportation systems, ports and inland transport facilities should all be integrated into one coordinated plan. More specifically, a method to schedule different types of handling equipment in an integrated way within a container terminal is a popular topic for researchers. However, not many researchers have addresses this topic in relationship to the simulation aspect which will test feasible solutions under real container terminal environment parameters. In order to increase the efficiency of operations, the development of mathematical models and algorithms is critical in finding the best feasible solution. The objective of this study is to evaluate the feasible solution to find the proper number of Yard Trailers (YTs) with the minimal cost for the container terminals. This study uses the Dynamic YTs operation's method as a background for modeling. A mathematical model with various constraints related to the integrated operations among the different types of handling equipment is formulated. This model takes into consideration both serving time of quay cranes and yard cranes, and cost reduction strategies by decreasing use of YTs with the specific objective of minimum total cost including utilization of YTs and vessel berthing. In addition, a heuristic algorithm combined with Monte Carlo Method and Brute-Force Search are employed. The early Stage Technique of Monte Carlo method is proposed to generate vast random numbers to replicate simulation for real cases., The Brute-Force Search is used for identifying all potential cases specific to the conditions of this study. Some preliminary numerical test results suggest that this method is good for use in conjunction with simulation of container terminal operation. The expected outcome of this research is a solution to obtain the proper number of YTs for transporting containers with a minimum cost; thus, improving the operational efficiency in a container terminal.
Show less - Date Issued
- 2011
- PURL
- http://purl.flvc.org/FAU/3174315
- Subject Headings
- Marine terminals, Computer programs, Computer algorithms, Materials management, Warehouses, Management, Transportation engineering, Freight and freightage
- Format
- Document (PDF)
- Title
- Implementation of a fuzzy-logic-based trust model.
- Creator
- Zhao, Yuanhui., Florida Atlantic University, Zhuang, Hanqi, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
-
In the last 10 years, due to the rapid developments in computers and Internet, the Electronic Commerce has advanced significantly. More and more companies have shifted their businesses activities to the Internet. However, the popular use of ecommerce has also raised serious security problems. Therefore developing security schemes has become a key issue both in the academic as well as industrial research. Since the Internet is open to the public, the associated security issue is challenging. A...
Show moreIn the last 10 years, due to the rapid developments in computers and Internet, the Electronic Commerce has advanced significantly. More and more companies have shifted their businesses activities to the Internet. However, the popular use of ecommerce has also raised serious security problems. Therefore developing security schemes has become a key issue both in the academic as well as industrial research. Since the Internet is open to the public, the associated security issue is challenging. A good security strategy should not only protect the vendors' interest, but also enhance the mutual trust between vendors and customers. As a result, the people will feel more confident in conducting e-commerce. This thesis is dedicated to develop a fuzzy-logic based trust model. In general, the ecommerce transactions need costly verification and authentication process. In some cases, it is not cost effective to verify and authenticate each transaction, especially for transactions involving only small amount of money and for customers having an excellent transaction history. In view of this, in this research a model that distinguishes potentially safe transactions from unsafe transactions is developed. Only those potentially unsafe transactions need to be verified and authenticated. The model takes a number of fuzzy variables as inputs. However, this poses problems in constructing the trust table since the number of fuzzy rules will increase exponentially as the number of fuzzy variables increase. To make the problem more trackable, the variables are divided into several groups, two for each table. Each table will produce a decision on trust. The final decision is made based on the "intersection" of all these outputs. Simulation studies have been conducted to validate the effectiveness of the proposed trust model. Therefore simulations, however, need to be tested in a real business environment using real data. Relevant limitations on the proposed model are hence discussed and future research direction is indicated.
Show less - Date Issued
- 2001
- PURL
- http://purl.flvc.org/fcla/dt/12812
- Subject Headings
- Fuzzy logic, Electronic commerce--Security measures
- Format
- Document (PDF)
- Title
- Dynamic modeling of two layered stratification.
- Creator
- Zhang, Yaodong., Florida Atlantic University, Scarlatos, Panagiotis (Pete) D., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
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In this thesis, a two-dimensional in the vertical plane numerical model has been developed for simulation of the free surface and density interface profiles due to a wind shear stress applied on a stratified water body, such as lake or reservoir. The results agreed qualitatively and quantitatively with our experimental results, as well as with the work of other researchers. A computer algorithm is established that can be used to estimate the shear stress along the interface and the velocity...
Show moreIn this thesis, a two-dimensional in the vertical plane numerical model has been developed for simulation of the free surface and density interface profiles due to a wind shear stress applied on a stratified water body, such as lake or reservoir. The results agreed qualitatively and quantitatively with our experimental results, as well as with the work of other researchers. A computer algorithm is established that can be used to estimate the shear stress along the interface and the velocity field throughout the water body. The model can be applied for prediction of wind-induced mixing processes in elongated lakes or reservoirs.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/14809
- Subject Headings
- Upwelling, Turbulence, Density currents
- Format
- Document (PDF)
- Title
- Modeling of bracelet anodes and anode arrays for pipeline CP systems.
- Creator
- Zhang, Xiaolin., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
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Two models for pipeline bracelet anodes depletion with time were analyzed: one with uniform corrosion and the other with localized corrosion. The potential of the pipeline was determined to become more positive with time due to corrosion of the anode. The pipeline protected by the anode with localized corrosion had more a positive potential than the one protected by the anode with uniform corrosion. A method based upon the equations of Sunde was developed for determining resistance of linear...
Show moreTwo models for pipeline bracelet anodes depletion with time were analyzed: one with uniform corrosion and the other with localized corrosion. The potential of the pipeline was determined to become more positive with time due to corrosion of the anode. The pipeline protected by the anode with localized corrosion had more a positive potential than the one protected by the anode with uniform corrosion. A method based upon the equations of Sunde was developed for determining resistance of linear and rectangular anode arrays. Accuracy of this approach was evaluated using Boundary Element Modeling (BEM). The difference between the two methods was defined as Error. A corrected function of Sunde's equation was developed in order to get a more accurate resistance of a 1 x N anode array. The influence on resistance of a M x N (M < N) anode array of anode size, separation distance and array number was analyzed. Error increased with increasing anode size and decreased with increasing number of anodes and separation distance. The application and limitations of commonly used anode resistance formulas are discussed.
Show less - Date Issued
- 2003
- PURL
- http://purl.flvc.org/fcla/dt/13087
- Subject Headings
- Pipelines--Cathodic protection, Corrosion and anti-corrosives, Underwater pipelines, Anodes
- Format
- Document (PDF)
- Title
- A VLSI implementable thinning algorithm.
- Creator
- Zhang, Wei, Florida Atlantic University, Shankar, Ravi, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
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Thinning is a very important step in a Character Recognition System. This thesis evolves a thinning algorithm that can be hardware implemented to improve the speed of the process. The software thinning algorithm features a simple set of rules that can be applied on both hexagonal and orthogonal character images. The hardware architecture features the SIMD structure, simple processing elements and near neighbor communications. The algorithm was simulated against the U.S. Postal Service...
Show moreThinning is a very important step in a Character Recognition System. This thesis evolves a thinning algorithm that can be hardware implemented to improve the speed of the process. The software thinning algorithm features a simple set of rules that can be applied on both hexagonal and orthogonal character images. The hardware architecture features the SIMD structure, simple processing elements and near neighbor communications. The algorithm was simulated against the U.S. Postal Service Character Database. The architecture, evolved with consideration of both the software constraints and the physical layout limitations, was simulated using VHDL hardware description language. Subsequent to VLSI design and simulations the chip was fabricated. The project provides for a feasibility study in utilizing the parallel processor architecture for the implementation of a parallel image thinning algorithm. It is hoped that such a hardware implementation will speed up the processing and lead eventually to a real time system.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/14837
- Subject Headings
- Optical character recognition devices--Computer simulation, Algorithms, Integrated circuits--Very large scale integration
- Format
- Document (PDF)
- Title
- A parallel and reliable robot controller system.
- Creator
- Zhang, Ruiguang., Florida Atlantic University, Fernandez, Eduardo B., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
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In recent years robots have become increasingly important in many areas. Along with the development of robot-arm control theory, there has been an increased demand for faster and more reliable control systems. In this thesis, a parallel technique is applied to all of the units of a robot control system. Also, software fault-tolerance mechanisms such as timeout, conversation, exception handling, and their Occam implementations, are considered. A simulation study shows that pipelining, together...
Show moreIn recent years robots have become increasingly important in many areas. Along with the development of robot-arm control theory, there has been an increased demand for faster and more reliable control systems. In this thesis, a parallel technique is applied to all of the units of a robot control system. Also, software fault-tolerance mechanisms such as timeout, conversation, exception handling, and their Occam implementations, are considered. A simulation study shows that pipelining, together with a multiprocessing system, increases the performance of this real-time system, and it is a convenient way to speed up robot controller execution. While we have not evaluated the increase in reliability, we have shown that these fault tolerance mechanisms can be conveniently implemented in this type of application.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14566
- Subject Headings
- Control theory, Robots--Programming
- Format
- Document (PDF)
- Title
- Stochastic earthquake ground motion modeling.
- Creator
- Zhang, Ruichong., Florida Atlantic University, Lin, Y. K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
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A model for earthquake ground motion is developed in this dissertation using principles of geophysics and stochastics. The earth is idealized as being composed of horizontally stratified layers, with uniform physical properties for each layer. The seismic source is assumed to be the result of shear dislocation propagating on a fault line, which is further discretized into a series of point sources at equal intervals. The fundamental problem of the ground motion in a layered medium due to a...
Show moreA model for earthquake ground motion is developed in this dissertation using principles of geophysics and stochastics. The earth is idealized as being composed of horizontally stratified layers, with uniform physical properties for each layer. The seismic source is assumed to be the result of shear dislocation propagating on a fault line, which is further discretized into a series of point sources at equal intervals. The fundamental problem of the ground motion in a layered medium due to a point source at a given source location is first considered. The governing equations of three-dimensional wave motion in a uniform layer are presented and solved in both Cartesian and cylindrical coordinates. Wave propagation in a multi-layered medium is then analyzed in detail, in which the wave scattering matrices are introduced so that stability and accuracy in numerical calculation can be guaranteed. A detailed review of the mechanism of seismic point source is also provided. Based on the fundamental solution for a point source, an earthquake model is constructed by superposing the solutions associated with a series of point sources along a line which are activated sequentially at random times. Statistical characteristics of earthquake ground motion is then obtained by applying a generalized version of the random-pulse-train theory and its evolutionary spectral representation. Finally the effects of uneven interface on the earthquake ground motion is also analyzed using a first-order perturbation approach.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/12290
- Subject Headings
- Earth movements, Earthquakes, Stochastic processes
- Format
- Document (PDF)