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- Title
- GRAPH-THEORETIC APPROACH TO MODELING PROPAGATION AND CONTROL OF NETWORK WORMS.
- Creator
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Nikoloski, Zoran, Deo, Narsingh, University of Central Florida
- Abstract / Description
-
In today's network-dependent society, cyber attacks with network worms have become the predominant threat to confidentiality, integrity, and availability of network computing resources. Despite ongoing research efforts, there is still no comprehensive network-security solution aimed at controling large-scale worm propagation. The aim of this work is fivefold: (1) Developing an accurate combinatorial model of worm propagation that can facilitate the analysis of worm control strategies, (2)...
Show moreIn today's network-dependent society, cyber attacks with network worms have become the predominant threat to confidentiality, integrity, and availability of network computing resources. Despite ongoing research efforts, there is still no comprehensive network-security solution aimed at controling large-scale worm propagation. The aim of this work is fivefold: (1) Developing an accurate combinatorial model of worm propagation that can facilitate the analysis of worm control strategies, (2) Building an accurate epidemiological model for the propagation of a worm employing local strategies, (3) Devising distributed architecture and algorithms for detection of worm scanning activities, (4) Designing effective control strategies against the worm, and (5) Simulation of the developed models and strategies on large, scale-free graphs representing real-world communication networks. The proposed pair-approximation model uses the information about the network structure--order, size, degree distribution, and transitivity. The empirical study of propagation on large scale-free graphs is in agreement with the theoretical analysis of the proposed pair-approximation model. We, then, describe a natural generalization of the classical cops-and-robbers game--a combinatorial model of worm propagation and control. With the help of this game on graphs, we show that the problem of containing the worm is NP-hard. Six novel near-optimal control strategies are devised: combination of static and dynamic immunization, reactive dynamic and invariant dynamic immunization, soft quarantining, predictive traffic-blocking, and contact-tracing. The analysis of the predictive dynamic traffic-blocking, employing only local information, shows that the worm can be contained so that 40\% of the network nodes are not affected. Finally, we develop the Detection via Distributed Blackholes architecture and algorithm which reflect the propagation strategy used by the worm and the salient properties of the network. Our distributed detection algorithm can detect the worm scanning activity when only 1.5% of the network has been affected by the propagation. The proposed models and algorithms are analyzed with an individual-based simulation of worm propagation on realistic scale-free topologies.
Show less - Date Issued
- 2005
- Identifier
- CFE0000640, ucf:46521
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000640
- Title
- REDUCTION OF VORTEX-DRIVEN OSCILLATIONS IN A SOLID ROCKET MOTOR COLD FLOW SIMULATION THROUGH ACTIVE CONTROL.
- Creator
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Ward, Jami, Leonessa, Alexander, University of Central Florida
- Abstract / Description
-
Control of vortex-driven instabilities was demonstrated via a scaled-down, cold-flow simulation that modeled closed-end acoustics. When vortex shedding frequencies couple with the natural acoustic modes of a choked chamber, potentially damaging low-frequency instabilities may arise. Although passive solutions can be effective, an active control solution is preferable. An experiment was performed to demonstrate an active control scheme for the reduction of vortex-driven oscillations. A non...
Show moreControl of vortex-driven instabilities was demonstrated via a scaled-down, cold-flow simulation that modeled closed-end acoustics. When vortex shedding frequencies couple with the natural acoustic modes of a choked chamber, potentially damaging low-frequency instabilities may arise. Although passive solutions can be effective, an active control solution is preferable. An experiment was performed to demonstrate an active control scheme for the reduction of vortex-driven oscillations. A non-reacting experiment using a primary flow of air, where both the duct exit and inlet are choked, simulated the closed-end acoustics. Two plates, separated by 1.27 cm, produced the vortex shedding phenomenon at the chamber's first longitudinal mode. Two active control schemes, closed-loop and open-loop, were studied via a cold-flow simulation for validating the effects of reducing vortex shedding instabilities in the system. Actuation for both control schemes was produced by using a secondary injection method. The actuation system consisted of pulsing compressed air from a modifed, 2-stroke model airplane engine, controlled and powered by a DC motor. The use of open-loop only active control was not highly effective in reducing the amplitude of the first longitudinal acoustic mode, near 93 Hz, when the secondary injection was pulsed at the same modal frequency. This was due to the uncontrolled phasing of the secondary injection system. A Pulse Width Modulated (PWM) signal was added to the open-loop control scheme to correct for improper phasing of the secondary injection flow relative to the primary flow. This addition allowed the motor speed to be intermittently increased to a higher RPM before returning to the desired open-loop control state. This proved to be effective in reducing the pressure disturbance by approximately 46%. A closed-loop control scheme was then test for its effectiveness in controlling the phase of the secondary injection. Feedback of the system's state was determined by placing a dynamic pressure transducer near the chamber exit. Closed-loop active control, using the designed secondary injection system, was proven as an effective means of reducing the problematic instabilities. A 50% reduction in the FFT RMS amplitude was realized by utilizing a Proportional-Derivative controller to modify the phase of the secondary injection.
Show less - Date Issued
- 2006
- Identifier
- CFE0000920, ucf:46728
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000920
- Title
- THE EFFECTS ON OPERATOR PERFORMANCE AND WORKLOAD WHEN GUNNERY AND ROBOTIC CONTROL TASKS ARE PERFORMED CONCURRENTLY.
- Creator
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Joyner, Carla, McCauley-Bell, Pamela, University of Central Florida
- Abstract / Description
-
The purpose of this research was to examine operator workload and performance in a high risk, multi-task environment. Specifically, the research examined if a gunner of a Future Combat System, such as a Mounted Combat System, could effectively detect targets in the immediate environment while concurrently operating robotic assets in a remote environment. It also analyzed possible effects of individual difference factors, such as spatial ability and attentional control, on operator performance...
Show moreThe purpose of this research was to examine operator workload and performance in a high risk, multi-task environment. Specifically, the research examined if a gunner of a Future Combat System, such as a Mounted Combat System, could effectively detect targets in the immediate environment while concurrently operating robotic assets in a remote environment. It also analyzed possible effects of individual difference factors, such as spatial ability and attentional control, on operator performance and workload. The experimental conditions included a gunner baseline and concurrent task conditions where participants simultaneously performed gunnery tasks and one of the following tasks: monitor an unmanned ground vehicle (UGV) via a video feed (Monitor), manage a semi-autonomous UGV, and teleoperate a UGV (Teleop). The analysis showed that the asset condition significantly impacted gunnery performance with the gunner baseline having the highest number of targets detected (M = 13.600 , SD = 2.353), and concurrent Teleop condition the lowest (M = 9.325 , SD = 2.424). The research also found that high spatial ability participants tended to detect more targets than low spatial ability participants. Robotic task performance was also affect by the asset condition. The results showed that the robotic target detection rate was lower for the concurrent task conditions. A significant difference was seen between the UGV-baseline (80.1%) when participants performed UGV tasks only and UGV-concurrent conditions (67.5%) when the participants performed UGV tasks concurrently with gunnery tasks. Overall, this study revealed that there were performance decrements for the gunnery tasks as well as the robotic tasks when the tasks were performed concurrently.
Show less - Date Issued
- 2006
- Identifier
- CFE0000979, ucf:46704
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000979
- Title
- CONTROL AND TOPOLOGY IMPROVEMENTS IN HALF-BRIDGE DC-DC CONVERTERS.
- Creator
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Deng, Songquan, Batarseh, Issa, University of Central Florida
- Abstract / Description
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Efficiency and transient response are two key requirements for DC-DC converters. Topology and control are two key topics in this dissertation. A variety of techniques for DC-DC converter performance improvement are presented in this work. Focusing on the efficiency issue, a variety of clamping techniques including both active and passive methods are presented after the ringing issues in DC-DC converters are investigated. By presenting the clamping techniques, a big variety of energy...
Show moreEfficiency and transient response are two key requirements for DC-DC converters. Topology and control are two key topics in this dissertation. A variety of techniques for DC-DC converter performance improvement are presented in this work. Focusing on the efficiency issue, a variety of clamping techniques including both active and passive methods are presented after the ringing issues in DC-DC converters are investigated. By presenting the clamping techniques, a big variety of energy management concepts are introduced. The active bridge-capacitor tank clamping and FET-diode-capacitor tank clamping are close ideas, which transfer the leakage inductor energy to clamping capacitor to prevent oscillation between leakage inductor and junction capacitor of MOSFETs. The two-FET-clamping tank employs two MOSFETs to freewheeling the leakage current when the main MOSFETs of the half-bridge are both off. Driving voltage variation on the secondary side Synchronous Rectifier (SR) MOSFETs in self-driven circuit due to input voltage variation in bus converter applications is also investigated. One solution with a variety of derivations is proposed using zerner-capacitor combination to clamping the voltage while maintaining reasonable power losses. Another efficiency improvement idea comes from phase-shift concept in DC-DC converters. By employing phase-shift scheme, the primary side and the secondary side two MOSFETs have complementary driving signals respectively, which allow the MOSFET to be turned on with Zero Voltage Switching (ZVS). Simulation verified the feasibility of the proposed phase-shifted DC-DC converter. From the control scheme point of view, a novel peak current mode control concept for half-bridge topologies is presented. Aiming at compensating the imbalanced voltage due to peak current mode control in symmetric half-bridge topologies, an additional voltage compensation loop is used to bring the half-bridge capacitor voltage back to balance. In the proposed solutions, one scheme is applied on symmetric half-bridge topology and the other one is applied on Duty-cycle-shifted (DCS) half-bridge topology. Both schemes employ simple circuitry and are suitable for integration. Loop stability issues are also investigated in this work. Modeling work shows the uncompensated half-bridge topology cannot be stabilized under all conditions and the additional compensation loop helps to prevent the voltage imbalance effectively.
Show less - Date Issued
- 2005
- Identifier
- CFE0000840, ucf:46674
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000840
- Title
- ACHIEVING COST-EFFECTIVE SUPPLY CHAIN AGILITY FOR THE SEMICONDUCTOR INDUSTRY.
- Creator
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Jeffery, Mariah, Butler, Renee, University of Central Florida
- Abstract / Description
-
Supply chain agility has been receiving a lot of attention in recent literature as a way for organizations to become more responsive to change and improve customer service levels. However, agility is typically dealt with qualitatively, and organizations are usually unsure of the steps to take to improve their agility and the customer service level to target. This research studies supply chain agility based on a case study of Intel Corporation, a large semiconductor manufacturer. Here, agility...
Show moreSupply chain agility has been receiving a lot of attention in recent literature as a way for organizations to become more responsive to change and improve customer service levels. However, agility is typically dealt with qualitatively, and organizations are usually unsure of the steps to take to improve their agility and the customer service level to target. This research studies supply chain agility based on a case study of Intel Corporation, a large semiconductor manufacturer. Here, agility is defined as the ability to satisfy customer demands by reacting effectively to changes in market stimuli. Reacting effectively does not mean reacting to every change in supply or demand. Doing so means increasing supply chain variability unnecessarily, which is amplified by the bullwhip effect. The essence of supply chain agility is determining the degree to which variability should be managed through artificial means such as safety stock, and appropriate triggers for changing production levels and inventory targets. The purpose of this research is to examine factors that influence supply chain agility and identify a cost-effective plan for achieving it. The first phase addresses the problem of identifying target inventory and customer service levels based on regression analysis of historical data and financial analysis of inventory holding costs and stock-out costs. The impact of three factors (forecast error, order lead-time, and demand variability) on the relationship between inventory and customer service level is also examined. The second phase of the research evaluates strategies for production and inventory control with the goal of finding the appropriate trade-off between minimizing cost (of holding inventory and stock-outs) and minimizing variability. Control policies based on the Exponentially Weighted Moving Average (EWMA) control chart with control limits on demand forecasts are proposed to detect when tighter control of processes is necessary. A Monte Carlo supply chain simulation is used to evaluate the performance of these policies under various levels of forecast error and demand variability. Results indicate that several control chart-based policies outperform Intel's current planning policy in terms of cost without significantly increasing variability. The selection of the appropriate policy must be based on the decision-makers' desire to minimize cost compared to the desire to minimize variability, as each policy results in a trade-off between these two objectives.
Show less - Date Issued
- 2005
- Identifier
- CFE0000853, ucf:46670
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000853
- Title
- QOS IN COGNITIVE PACKET NETWORKS: ADAPTIVE ROUTING, FLOW AND CONGESTION CONTROL.
- Creator
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Su, Pu, Gelenbe, Erol, University of Central Florida
- Abstract / Description
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With the emergence of various applications that have different Quality of Service (QoS) requirements, the capability of a network to support QoS becomes more and more important and necessary. This dissertation explores QoS in Cognitive Packet Networks (CPN) by using adaptive routing, flow and congestion control. We present a detailed description and analysis of our proposed routing algorithms based on single and multiple QoS constraints. An online estimation of packet loss rate over a path is...
Show moreWith the emergence of various applications that have different Quality of Service (QoS) requirements, the capability of a network to support QoS becomes more and more important and necessary. This dissertation explores QoS in Cognitive Packet Networks (CPN) by using adaptive routing, flow and congestion control. We present a detailed description and analysis of our proposed routing algorithms based on single and multiple QoS constraints. An online estimation of packet loss rate over a path is introduced. We implement and evaluate the adaptive routing scheme in an experimental CPN test-bed. Our experiments support our claims that the users can achieve their desired best-effort QoS through this routing scheme. We also propose a QoS-based flow and congestion control scheme that is built in the transport layer and specially designed to work with CPN to support users' QoS while remaining friendly to TCP. Theoretical models and experimental analysis are presented. Finally we experimentally demonstrate that the proposed flow and congestion control scheme can effectively control the input flows, react to the congestion and work with our proposed adaptive routing scheme to achieve users' QoS.
Show less - Date Issued
- 2005
- Identifier
- CFE0000813, ucf:46685
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000813
- Title
- UNIFIED LARGE AND SMALL SIGNAL DISCRETE-SPACE MODELING FOR PWM CONVERTERS IN CCM.
- Creator
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Shoubaki, Ehab, Batarseh, Issa, University of Central Florida
- Abstract / Description
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In this Thesis a Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulations of the converter switches , and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulations , this approach yields both a large signal nonlinear discrete model and...
Show moreIn this Thesis a Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulations of the converter switches , and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulations , this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic analysis of the converter states at steady-state is done for steady-state waveform acquisition , which increases the accuracy of the model especially for finding the control to inductor current frequency response. Finally the Discrete model is verified for the Half-Bridge DC/DC topology for its three main control schemes (Asymmetric , Symmetric , DCS). A GUI platform in MATLAB is presented as a wrapper that utilizes the models and analysis presented in this thesis.
Show less - Date Issued
- 2005
- Identifier
- CFE0000710, ucf:46607
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000710
- Title
- DIGITAL CONTROL OF HALF-BRIDGE DC-DC CONVERTERS WITH CURRENT DOUBLER RECTIFICATION.
- Creator
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Yao, Liangbin, Batarseh, Issa, University of Central Florida
- Abstract / Description
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DC-DC power converters play an important role in powering telecom and computing systems. Complex systems, including power electronics systems, are increasingly using digital controllers because of the major advancements in digital controllers and DSP as well as there ability to perform sophisticated and enhanced control schemes. In this thesis, the digital controller is investigated for DC-DC converters in high current low voltage applications. For an optimal design of a regulated DC-DC...
Show moreDC-DC power converters play an important role in powering telecom and computing systems. Complex systems, including power electronics systems, are increasingly using digital controllers because of the major advancements in digital controllers and DSP as well as there ability to perform sophisticated and enhanced control schemes. In this thesis, the digital controller is investigated for DC-DC converters in high current low voltage applications. For an optimal design of a regulated DC-DC converter, it is necessary to derive a valid model. The current doubler rectified half bridge (CDRHB) DC-DC converter is suitable for high current low voltage applications. In this thesis, the topology operations are analyzed and then the unified state space model, analog small signal model and digital small signal model are derived. Then the digital compensator design is discussed as well as the analog-digital converter (ADC) and the digital pulse-width-modulator (DPWM) design rules. In addition, voltage driving optimization is proposed for the benefit of the digital controller. Finally, experimental results based on the CDRHB are presented and analyzed.
Show less - Date Issued
- 2005
- Identifier
- CFE0000706, ucf:46626
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000706
- Title
- AUTONOMOUS CONTROLS ALGORITHMFOR FORMATION FLYING OF SATELLITES.
- Creator
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Santiago, Luis, Johnson, Roger, University of Central Florida
- Abstract / Description
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This document describes the design and analysis of the Navigation, Guidance and Control System for the KnightSat project. The purpose for the project is to test and demonstrate new technologies the Air Force would be interested in for research and development. The primary mission of KnightSat is to show how a constellation of satellites can maintain relative position with each other autonomously using the Microwave Electro Thermal (MET) thruster. The secondary mission is to use multiple...
Show moreThis document describes the design and analysis of the Navigation, Guidance and Control System for the KnightSat project. The purpose for the project is to test and demonstrate new technologies the Air Force would be interested in for research and development. The primary mission of KnightSat is to show how a constellation of satellites can maintain relative position with each other autonomously using the Microwave Electro Thermal (MET) thruster. The secondary mission is to use multiple satellite imagery to obtain 3 dimensional stereo photographs of observable terrain. Formation flying itself has many possible uses for future applications. Selected missions that require imaging or data collection can be more economically accomplished using smaller multiple satellites. The MET thruster is a very efficient, but low thrust alternative that can provide thrust for a very long time, hence provide the low thrust necessary to maintain the satellites at a constant separation. The challenge is to design a working control algorithm to provide the desired output data to be used to command the MET thrusters. The satellites are to maintain a constant relative distance from each other, and use the least amount of fuel possible. If one satellite runs out of fuel before the other, it would render the constellation less useful or useless. Hence, the satellites must use the same amount of fuel in order to maintain an optimal operational duration on orbit.
Show less - Date Issued
- 2006
- Identifier
- CFE0001171, ucf:46854
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001171
- Title
- THE INFLUENCE OF GUN CONTROL LEGISLATION ON RAMPAGE SHOOTINGS.
- Creator
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Manor, Andrew, Beckman, James, University of Central Florida
- Abstract / Description
-
The United States has experienced several mass shootings in the past few years. It has been averaging one shooting every week in 2015, and something must be done about it. This problem appears to be limited to the United States since several other nations have been able to minimize, and almost eliminate the number of mass shootings. By taking an analysis of the gun laws of the United States with those of Australia and Canada it can be concluded that some aspects of strict gun control can...
Show moreThe United States has experienced several mass shootings in the past few years. It has been averaging one shooting every week in 2015, and something must be done about it. This problem appears to be limited to the United States since several other nations have been able to minimize, and almost eliminate the number of mass shootings. By taking an analysis of the gun laws of the United States with those of Australia and Canada it can be concluded that some aspects of strict gun control can reduce the number of mass shootings. Further, the United States should look at what other common law nations have done to reduce the number of mass shootings. The United States is also the only nation that recognizes a fundamental right to keep and bear arms, and any legislation must address that right. Some ways to address strict gun control in the United States is to strengthen the background check system, add a liability insurance requirement, and strictly enforce culpable negligent statutes. Adding some elements of strict gun control will help minimize the amount, and impact of the shootings. Canada, and Australia both have active hunting communities that require the need for some legal firearms. A night at the movies, a day at school, or attending a church event should not bring about worry that an individual may get shot and killed by a deranged individual. Other similar nations have shown that rampage shootings do not have to be a side effect of living in a free society.
Show less - Date Issued
- 2015
- Identifier
- CFH0004868, ucf:45456
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004868
- Title
- Analysis of Remote Tripping Command Injection Attacks in Industrial Control Systems Through Statistical and Machine Learning Methods.
- Creator
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Timm, Charles, Caulkins, Bruce, Wiegand, Rudolf, Lathrop, Scott, University of Central Florida
- Abstract / Description
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In the past decade, cyber operations have been increasingly utilized to further policy goals of state-sponsored actors to shift the balance of politics and power on a global scale. One of the ways this has been evidenced is through the exploitation of electric grids via cyber means. A remote tripping command injection attack is one of the types of attacks that could have devastating effects on the North American power grid. To better understand these attacks and create detection axioms to...
Show moreIn the past decade, cyber operations have been increasingly utilized to further policy goals of state-sponsored actors to shift the balance of politics and power on a global scale. One of the ways this has been evidenced is through the exploitation of electric grids via cyber means. A remote tripping command injection attack is one of the types of attacks that could have devastating effects on the North American power grid. To better understand these attacks and create detection axioms to both quickly identify and mitigate the effects of a remote tripping command injection attack, a dataset comprised of 128 variables (primarily synchrophasor measurements) was analyzed via statistical methods and machine learning algorithms in RStudio and WEKA software respectively. While statistical methods were not successful due to the non-linearity and complexity of the dataset, machine learning algorithms surpassed accuracy metrics established in previous research given a simplified dataset of the specified attack and normal operational data. This research allows future cybersecurity researchers to better understand remote tripping command injection attacks in comparison to normal operational conditions. Further, an incorporation of the analysis has the potential to increase detection and thus mitigate risk to the North American power grid in future work.
Show less - Date Issued
- 2018
- Identifier
- CFE0007257, ucf:52193
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007257
- Title
- Measuring Player Perceptions of Freedom and Control in Modded and Unmodded Versions of Bethesda's Skyrim: A Qualitative Play Study.
- Creator
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Kretzschmar, Mark, Salter, Anastasia, Stanfill, Mel, Janz, Bruce, Postigo, Hector, University of Central Florida
- Abstract / Description
-
This interdisciplinary dissertation explores perceptions of control in modded and unmodded versions of Bethesda's sandbox video game Skyrim. Sandbox games are known for greater choice options that suggest greater perceptions of control for gamers. Sandbox games also generally encourage the use of user-generated creations called modifications (mods) that users can download to personalize their games. While we need philosophy to understand and define control as a concept, we also need...
Show moreThis interdisciplinary dissertation explores perceptions of control in modded and unmodded versions of Bethesda's sandbox video game Skyrim. Sandbox games are known for greater choice options that suggest greater perceptions of control for gamers. Sandbox games also generally encourage the use of user-generated creations called modifications (mods) that users can download to personalize their games. While we need philosophy to understand and define control as a concept, we also need psychology to understand how users perceive control in media studies. At present, qualitative academic research that measures gamer perceptions of control is non-existent as is research on how users articulate their experiences with mods. Interviews were conducted with twenty-seven individuals who identified as gamers to analyze these perceptions of control in a game like Skyrim. The first chapter is introductory and outlines key terms for the dissertation as well as the play study's methodology. The second chapter examines philosophical and psychological perceptions of control that correspond with negative freedom (freedom from) and positive freedom (freedom to). While no game can promise radical free will because they have been programmed in advance, the information here may be used to demonstrate how perceptions of control might influence game design. The third chapter continues this exploration of perceived control through genre analysis, revealing the relationship between greater perceptions of control and mod support in sandbox video games. The fourth chapter presents the first two findings from the play study that demonstrate how mods influence player perceptions of control. The fifth chapter reveals how gamers of the play study discuss their perceptions of control video games in their own words with an emphasis on positive and negative freedom and generic conventions. The final chapter provides challenges for game design and scholarly qualitative analysis for future research based on findings in the play study.
Show less - Date Issued
- 2019
- Identifier
- CFE0007479, ucf:52673
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007479
- Title
- Modeling and Transient Simulation of a Fully Integrated Multi-Pressure Heat Recovery Steam Generator Using Siemens T3000.
- Creator
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McConnell, Jonathan, Das, Tuhin, Chow, Louis, Tian, Tian, University of Central Florida
- Abstract / Description
-
The focus of this research is on the transient thermodynamic properties and dynamic behavior of a Heat Recovery Steam Generator (HRSG). An HRSG is a crossflow heat exchanger designed for the extraction of energy from the hot exhaust gas of a traditional power plant through boiling induced phase change. Superheated steam is sent through a turbine to generate additional power, raising the overall efficiency of a power plant. The addition of renewable energies and the evolution of smart grids...
Show moreThe focus of this research is on the transient thermodynamic properties and dynamic behavior of a Heat Recovery Steam Generator (HRSG). An HRSG is a crossflow heat exchanger designed for the extraction of energy from the hot exhaust gas of a traditional power plant through boiling induced phase change. Superheated steam is sent through a turbine to generate additional power, raising the overall efficiency of a power plant. The addition of renewable energies and the evolution of smart grids have brought forth a necessity to gain a comprehensive understanding of transient behavior within an HRSG in order to efficiently manage the power output of traditional plants. Model-based techniques that can simulate a wide range of operating conditions can be valuable and insightful. For this reason, a multi-physics model of an HRSG has been developed in Siemens T3000 plant monitoring software. The layout and conditions of a reference HRSG have been provided by Siemens Energy Inc. along with validation data for behavioral comparison. The HRSG selected is a three pressure stage HRSG. Simultaneous simulation of these three pressure systems and their interactions has been achieved. A potential for real time execution was demonstrated. An HRSG is built of three major subsystems, namely economizers, boilers, and superheaters. A lumped control volume approach has been implemented to efficiently model the energy and mass balances of medium within each subsystem. In this effort, considering the goal of real time simulation, special attention was paid to balance computational burden with numerical accuracy.A major focus of this research has been accurately modeling the complexities of phase change within a boiler subsystem. A switching mechanism has been developed to numerically model the dynamic heating and evaporation of boiler liquid. To increase robustness of the model to numerical fluctuations and perturbations, bidirectional flow comprising of boiling and condensation was modeled with the switching mechanism. This numerically robust model shows good agreement with the validation data provided by Siemens.
Show less - Date Issued
- 2019
- Identifier
- CFE0007683, ucf:52459
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007683
- Title
- Bio-Inspired Visual Servo Control of a Picking Mechanism in an Agricultural Ground Robot.
- Creator
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Defterli, Sinem, Xu, Yunjun, Kauffman, Jeffrey L., Lin, Kuo-Chi, Song, Sang-Eun, Zheng, Qipeng, University of Central Florida
- Abstract / Description
-
For a recently constructed disease detection agricultural ground robot, the segregation of unhealthy leaves fromstrawberry plants is a major task of the robot's manipulation subsystem in field operations. In this dissertation, the motion planning of a custom-designedpicking mechanism in the ground robot's subsystem is studied in two sections. First, a set of analytical, suboptimal semi-analyticaland numerical algorithms are studied to solve the inverse kinematics problem of the handling...
Show moreFor a recently constructed disease detection agricultural ground robot, the segregation of unhealthy leaves fromstrawberry plants is a major task of the robot's manipulation subsystem in field operations. In this dissertation, the motion planning of a custom-designedpicking mechanism in the ground robot's subsystem is studied in two sections. First, a set of analytical, suboptimal semi-analyticaland numerical algorithms are studied to solve the inverse kinematics problem of the handling mechanism in firmcircumstances. These premeditated approaches are built on the computation of the joint variables by an identified 3Dposition data of the target leaf only. The outcomes of the three solution algorithms are evaluated in terms of the performanceindexes of energy change and the CPU time cost. The resultant postures of the mechanism for different target pointlocations are observed both in simulations and the hardware experiments with each IK solution. Secondly, after the manipulation task of the mechanism via the proposed inverse kinematicalgorithms is performed, some compensation may be needed due to the sudden and unpredicted deviation of the targetposition under field conditions.For the purpose of finding optimal joint values under certain constraints, a trajectory optimization problem in image-based visual servoing method via the camera-in-handconfiguration is initiated when the end-effector is in the close proximity of the target leaf. In this part of the study, a bio-inspired trajectory optimization problem in image-basedvisual servoing method is constructed based on the mathematical model derived from the prey-predatorrelationships in nature. In this biological phenomenon, the predator constructs its path in a certain subspace whilecatching the prey. When this motion strategy is applied to trajectory optimization problems, it causes a significantreduce in the computation cost since it finds the optimum solution in a certain manifold. The performance of the introducedbio-inspired trajectory optimization in visual servoing is validated with the hardware experiments both in laboratory settings and in fieldconditions.
Show less - Date Issued
- 2018
- Identifier
- CFE0007170, ucf:52247
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007170
- Title
- Design and Optimization of a Wave Energy Harvester Utilizing a Flywheel Energy Storage System.
- Creator
-
Helkin, Steven, Lin, Kuo-Chi, Gordon, Ali, Raghavan, Seetha, University of Central Florida
- Abstract / Description
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This thesis details the design and optimization of a buoy used to collect renewable energy from ocean waves. The proposed buoy is a point absorber(-)a device that transforms the kinetic energy of the vertical motion of surface waves into electrical energy. The focus of the research is on the mechanical system used to collect the energy, and methods to improve it for eventual use in an actual wave energy harvester. A flywheel energy storage system was utilized in order to provide an improved...
Show moreThis thesis details the design and optimization of a buoy used to collect renewable energy from ocean waves. The proposed buoy is a point absorber(-)a device that transforms the kinetic energy of the vertical motion of surface waves into electrical energy. The focus of the research is on the mechanical system used to collect the energy, and methods to improve it for eventual use in an actual wave energy harvester. A flywheel energy storage system was utilized in order to provide an improved power output from the system, even with the intermittent input of force exerted by ocean waves. A series of laboratory prototypes were developed to analyze parameters that are important to the success of the point absorb mechanical system. By introducing a velocity-based load control scheme in conjunction with flywheel energy storage, it was seen that the average power output by the prototype was increased. The generator load is controlled via a relay switch that removes electrical resistance from the generator(-)this sacrifices time during which power is drawn from the system, but also allows the buoy to move with less resistance. A simulation model was developed in order to analyze the theoretical wave absorber system and optimize the velocity threshold parameters used in the load control. Results indicate that the power output by the system can be substantially improved through the use of a flywheel energy storage control scheme that engages and disengages the electrical load based on the rotational velocity of the flywheel system. The results of the optimization are given for varying-sized generator systems input into the simulation in order to observe the associated trends.
Show less - Date Issued
- 2011
- Identifier
- CFE0004118, ucf:49113
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004118
- Title
- STUDY OF DESIGN FOR RELIABILITY OF RF AND ANALOG CIRCUITS.
- Creator
-
Tang, Hongxia, Yuan, Jiann-Shiun, Wu, Xinzhang, Sundaram, Kalpathy, Chow, Lee, University of Central Florida
- Abstract / Description
-
Due to continued device dimensions scaling, CMOS transistors in the nanometer regime have resulted in major reliability and variability challenges. Reliability issues such as channel hot electron injection, gate dielectric breakdown, and negative bias temperature instability (NBTI) need to be accounted for in the design of robust RF circuits. In addition, process variations in the nanoscale CMOS transistors are another major concern in today's circuits design.An adaptive gate-source biasing...
Show moreDue to continued device dimensions scaling, CMOS transistors in the nanometer regime have resulted in major reliability and variability challenges. Reliability issues such as channel hot electron injection, gate dielectric breakdown, and negative bias temperature instability (NBTI) need to be accounted for in the design of robust RF circuits. In addition, process variations in the nanoscale CMOS transistors are another major concern in today's circuits design.An adaptive gate-source biasing scheme to improve the RF circuit reliability is presented in this work. The adaptive method automatically adjusts the gate-source voltage to compensate the reduction in drain current subjected to various device reliability mechanisms. A class-AB RF power amplifier shows that the use of a source resistance makes the power-added efficiency robust against threshold voltage and mobility variations, while the use of a source inductance is more reliable for the input third-order intercept point.A RF power amplifier with adaptive gate biasing is proposed to improve the circuit device reliability degradation and process variation. The performances of the power amplifier with adaptive gate biasing are compared with those of the power amplifier without adaptive gate biasing technique. The adaptive gate biasing makes the power amplifier more resilient to process variations as well as the device aging such as mobility and threshold voltage degradation. Injection locked voltage-controlled oscillators (VCOs) have been examined. The VCOs are implemented using TSMC 0.18 (&)#181;m mixed-signal CMOS technology. The injection locked oscillators have improved phase noise performance than free running oscillators.A differential Clapp-VCO has been designed and fabricated for the evaluation of hot electron reliability. The differential Clapp-VCO is formed using cross-coupled nMOS transistors, on-chip transformers/inductors, and voltage-controlled capacitors. The experimental data demonstrate that the hot carrier damage increases the oscillation frequency and degrades the phase noise of Clapp-VCO.A p-channel transistor only VCO has been designed for low phase noise. The simulation results show that the phase noise degrades after NBTI stress at elevated temperature. This is due to increased interface states after NBTI stress. The process variability has also been evaluated.
Show less - Date Issued
- 2012
- Identifier
- CFE0004223, ucf:49000
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004223
- Title
- AN OPTIMAL CONTROL APPROACH FOR DETERMINATION OF THE HEAT LOSS COEFFICIENT IN AN ICS SOLAR DOMESTIC WATER HEATING SYSTEM.
- Creator
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Gil, Camilo, Simaan, Marwan, University of Central Florida
- Abstract / Description
-
Water heating in a typical home in the U.S. accounts for a significant portion (between 14% and 25%) of the total homeÂÂÂÂ's annual energy consumption. The objective of considerably reducing the homeÂÂÂÂ's energy consumption from the utilities calls for the use of onsite renewable energy...
Show moreWater heating in a typical home in the U.S. accounts for a significant portion (between 14% and 25%) of the total homeÂÂÂÂ's annual energy consumption. The objective of considerably reducing the homeÂÂÂÂ's energy consumption from the utilities calls for the use of onsite renewable energy systems. Integral Collector Storage (ICS) solar domestic water heating systems are an alternative to help meet the hot water energy demands in a household. In order to evaluate the potential benefits and contributions from the ICS system, it is important that the parameter values included in the model used to estimate the systemÂÂÂÂ's performance are as accurate as possible. The overall heat loss coefficient (Uloss) in the model plays an important role in the performance prediction methodology of the ICS. This work presents a new and improved methodology to determine Uloss as a function of time in an ICS system using a systematic optimal control theoretic approach. This methodology is based on the derivation of a new nonlinear state space model of the system, and the formulation of a quadratic performance function whose minimization yields estimates of Uloss values that can be used in computer simulations to improve the performance prediction of the ICS system, depending on the desired time of the year and hot water draw profile. Simulation results show that predictions of the systemÂÂÂÂ's performance based on these estimates of Uloss are considerably more accurate than the predictions based on current existing methods for estimating Uloss.
Show less - Date Issued
- 2010
- Identifier
- CFE0003266, ucf:48525
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003266
- Title
- Evaluating Corrosion Control Alternatives for a Reverse Osmosis, Nanofiltration and Anion-Exchange Blended Water Supply.
- Creator
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Wilder, Rebecca, Duranceau, Steven, Randall, Andrew, Zhang, Husen, University of Central Florida
- Abstract / Description
-
The research reported herein describes the study activities performed by University of Central Florida (UCF) on behalf of the Town of Jupiter Water Utilities (Town). The Town recently changed its water treatment operations from a combination of reverse osmosis (RO), lime softening (LS) and anion-exchange (IX) to a combination of RO, IX and nanofiltration (NF). Although this treatment change provided enhanced water to the surrounding community in terms of better contaminant removal and reduced...
Show moreThe research reported herein describes the study activities performed by University of Central Florida (UCF) on behalf of the Town of Jupiter Water Utilities (Town). The Town recently changed its water treatment operations from a combination of reverse osmosis (RO), lime softening (LS) and anion-exchange (IX) to a combination of RO, IX and nanofiltration (NF). Although this treatment change provided enhanced water to the surrounding community in terms of better contaminant removal and reduced DBP formation potential, integration of the NF process altered finished water quality parameters including pH, alkalinity and hardness. There was concern that these changes could result in secondary impacts related to accelerated corrosion of distribution system components and subsequent regulatory compliance. In addition, replacement of the LS process altered the in-plant blending operations by creating an unstable intermediate blend composed of RO and IX waters. There were concerns that this intermediate blend was affecting the integrity of in-plant hydraulic conveyance components.UCF developed a corrosion monitoring study to assess the potential impacts related to internal corrosion, water quality and regulatory compliance after integrating NF into the existing water supply. The intended purpose was to further highlight the complexities of corrosion, describe a unique approach to corrosion monitoring as well as offer various recommendations for corrosion control in a system that relies on a blended water supply. Research was conducted in three phases to address the in-plant and distribution system corrosion issues separately and identify appropriate corrosion control treatment alternatives. The three test phases included: a baseline conditions assessment to compare corrosion of the intermediate RO-IX blend with the finished water blend (RO-IX-NF); an in-plant corrosion control evaluation; and a distribution system corrosion control evaluation.A test apparatus was constructed and operated at the Town's facilities to monitor corrosion activity of mild steel, copper and lead solder metal components. The test apparatus consisted of looped PVC pipe segments housed with electrochemical probes and metal coupons to monitor corrosion rates of the metallic components. Electrochemical probes containing metal electrodes were used to obtain instantaneous corrosion rates by means of the Linear Polarization Resistance (LPR) technique while the metal coupons were gravimetrically evaluated for weight loss. The electrochemical probes permitted daily monitoring of each metal's corrosion rates while metal coupons were analyzed at the conclusion of testing and used for comparison. Different test waters flowed through the corrosion rack according to each test phase and relative corrosion rates were compared to evaluate corrosion control techniques.Study findings indicated that the intermediate blend was more corrosive, in general, then the final blend; however, research also indicated that the final blend of water was increasing lead and copper concentrations within the distribution system. An orthophosphate corrosion inhibitor was evaluated for in-plant corrosion control. The inhibitor's performance was assessed by comparing mild steel corrosion rates with and without the chemical. In addition, secondary impacts related to introduction of the chemical were evaluated by pre-corroding the metallic components prior to the introduction of the inhibitor. Results indicated that the inhibitor marginally decreased corrosion rates and increased the turbidity of the water supply. Based on these observations, it was concluded that the inhibitor was not a viable solution for in-plant corrosion control. To resolve in-plant corrosion issues, recommendations were made for modification of in-plant blending operations to eliminate the corrosive intermediate blend from the process allowing the RO, IX and NF treated waters to be blended in a common location. The effectiveness of a poly/ortho blended phosphate chemical inhibitor was evaluated for reducing lead and copper corrosion to resolve distribution corrosion issues. A 50/50 poly/ortho blend was selected because of its analogous use in similar municipal water facilities. Metallic corrosion rates, particularly lead and copper, were compared with and without the inhibitor to assess the performance of the chemical. Like the previous test phase, the metallic components were pre-corroded prior to the chemical's introduction to determine if secondary impacts could result from its presence. Results indicated that lead and copper corrosion rates were lower in the presence of the inhibitor, and secondary impacts related to increased turbidity were not observed for this chemical. Based on these results, it was recommended that a poly/ortho blended phosphate be used to decrease lead and copper corrosion within the Town's distribution system.
Show less - Date Issued
- 2012
- Identifier
- CFE0004460, ucf:49349
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004460
- Title
- The Impact of Technology on Management Control: Degradation, Empowerment, or Technology Dominance?.
- Creator
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Canada, Joseph, Arnold, Vicky, Roberts, Robin, Sutton, Steven, Benford, Tanya, University of Central Florida
- Abstract / Description
-
The evolution of technology brings with it the evolution of business processes. Without a doubt, technology changes how work is performed. At first glance, workplace technology appears to be a great boon to society. However, research presents opposing views on how workplace technologies impact the individual. One perspective argues that organizations utilize technology to redesign work processes, such that the worker requires less skill, autonomy, and compensation. The opposing perspective...
Show moreThe evolution of technology brings with it the evolution of business processes. Without a doubt, technology changes how work is performed. At first glance, workplace technology appears to be a great boon to society. However, research presents opposing views on how workplace technologies impact the individual. One perspective argues that organizations utilize technology to redesign work processes, such that the worker requires less skill, autonomy, and compensation. The opposing perspective argues that organizations utilize technology to empower employees to improve efficiency and profits. This dissertation consists of three interrelated studies examining workplace technology's impact on decision makers. The first study examines the capability of an enterprise system to increase the application of scientific management techniques to middle management and, consequently, to degrade middle management's work by limiting their autonomy. The second study investigates the capability of an enterprise system to facilitate the empowerment of managers via mutual monitoring and social identification. The third study builds upon the first study by examining how limiting autonomy through technology impacts the intrinsic motivation of decision makers and, as a result, affects the decision making process. Study one applies labor process theory to explain how enterprise systems can degrade the work of middle management via scientific management techniques. The purpose of this study is to test if the expectations of labor process theory can be applied to enterprise systems. In order to test this assertion, a field survey utilizing 189 middle managers is employed and the data is analyzed using component based structural equation modeling. The results indicate that enterprise system integration increases two scientific management techniques, formalization and performance measurement, but do not reveal a significant relationship between enterprise system integration and routinization. Interestingly, the results also indicate that routinization is the only scientific management technique, of the three studied, that directly limits the autonomy of the middle managers. Although performance measurement does not reduce autonomy directly, performance measurement interacts with routinization to reduce autonomy. This study contributes to the enterprise system literature by demonstrating enterprise systems' ability to increase the degree of scientific management applied to middle management. It also contributes to labor process theory by revealing that routinization may be the scientific management technique that determines whether other control techniques are utilized in a manner consistent with labor process theory. The ability of an enterprise system to facilitate the application of Mary Parker Follett's managerial control concepts are investigated in the second study. Specifically, Follett theorizes that information sharing facilitates the internalization of group goals and empowers individuals to have more influence and be more effective. This study employs a survey of 206 managers to test the theoretical relationships. The results indicate that enterprise system integration increases information sharing in the form of mutual monitoring, consequently, leading to social identification among peer managers. Additionally, social identification among peer managers empowers managers to have more influence over the organization. The study contributes to empowerment research by acknowledging and verifying the role that social identification plays in translating an empowering work climate into empowered managers. The study's conclusion that enterprise system integration facilitates the application of Follett's managerial control concepts extends both enterprise system and managerial control literature. The third study builds upon study one by examining the affect that autonomy has upon the decision maker. This study marries self-determination theory and technology dominance theory to understand the role that self-determination, intrinsic motivation, and engagement have upon technology dominance. Self-determination theory asserts that higher degrees of self-determination increase intrinsic motivation. Furthermore, self-determination research finds that intrinsic motivation increases engagement, while technology dominance research indicates that lack of engagement is an antecedent of technology dominance. Thus, applying self-determination theory as a predictor of technology dominance suggests that autonomy and relatedness associated with a task increase the intrinsic motivation to complete that task and consequently increase engagement in the task. Task engagement, in turn, reduces the likelihood of technology dominance. The proposed theoretical model is tested experimentally with 83 junior level business students. The results do not support the theoretical model, however the findings reveal that intrinsic motivation does reduce the likelihood of technology dominance. This indicates that intrinsic motivation as a predictor of technology dominance should be further investigated. Additionally, the study contributes to technology dominance literature by exhibiting a more appropriate operationalization of the inappropriate reliance aspect of technology dominance. This dissertation reveals that various theories concerning workplace technology and management control techniques have both validity and limitations. Labor process theorists cannot assume that all technologies and management control techniques are utilized to undermine the employee's value to the organization, as Study 2 reveals that enterprise systems and mutual monitoring lead to empowered managers. Likewise, proponents of enterprise systems cannot assume that the integrated nature of enterprise systems is always utilized in an empowering manner, as Study 1 reveals the increased performance measurement through enterprise systems can be utilized to limit managers in a routinized job environment. While the third study was unable to determine that the control features in technology affect the intrinsic motivation to complete a task, the findings do reveal that intrinsic motivation is directly related to technology dominance. The findings and theoretical refinements demonstrate that workplace technology and management control have a complicated relationship with the employee and that the various theories concerning them cannot be applied universally.
Show less - Date Issued
- 2013
- Identifier
- CFE0004980, ucf:49569
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004980
- Title
- The utility of verbal display redundancy in managing pilot's cognitive load during controller-pilot voice communications.
- Creator
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Kratchounova, Daniela, Jentsch, Florian, Mouloua, Mustapha, Hancock, Peter, Wise, John, University of Central Florida
- Abstract / Description
-
Miscommunication between controllers and pilots, potentially resulting from a high pilot cognitive load, has been a causal or contributing factor in a large number of aviation accidents. In this context, failure to communicate can be attributed, among other factors, to an inadequate human-system interface design, the related high cognitive load imposed on the pilot, and poor performance reflected by a higher error rate. To date, voice radio remains in service without any means for managing...
Show moreMiscommunication between controllers and pilots, potentially resulting from a high pilot cognitive load, has been a causal or contributing factor in a large number of aviation accidents. In this context, failure to communicate can be attributed, among other factors, to an inadequate human-system interface design, the related high cognitive load imposed on the pilot, and poor performance reflected by a higher error rate. To date, voice radio remains in service without any means for managing pilot cognitive load by design (as opposed to training or procedures). Such an oversight is what prompted this dissertation. The goals of this study were (a) to investigate the utility of a voice-to-text transcription (V-T-T) of ATC clearances in managing pilot's cognitive load during controller-pilot communications within the context of a modern flight deck environment, and (b) to validate whether a model of variable relationships which is generated in the domain of learning and instruction would (")transfer("), and to what extend, to an operational domain. First, within the theoretical framework built for this dissertation, all the pertaining factors were analyzed. Second, by using the process of synthesis, and based on guidelines generated from that theoretical framework, a redundant verbal display of ATC clearances (i.e., a V-T-T) was constructed. Third, the synthesized device was empirically examined. Thirty four pilots participated in the study (-) seventeen pilots with 100-250 total flight hours and seventeen with (>)500 total flight hours. All participants had flown within sixty days prior to attending the study. The experiment was conducted one pilot at a time in 2.5-hour blocks. A 2 Verbal Display Redundancy (no-redundancy and redundancy) X 2 Verbal Input Complexity (low and high) X 2 Level of Expertise (novices and experts) mixed-model design was used for the study with 5 IFR clearances in each Redundancy X Complexity condition. The results showed that the amounts of reduction of cognitive load and improvement of performance, when verbal display redundancy was provided, were in the range of about 20%. These results indicated that V-T-T is a device which has a tremendous potential to serve as (a) a pilot memory aid, (b) a way to verify a clearance has been captured correctly without having to make a (")Say again(") call, and (c) to ultimately improve the margin of safety by reducing the propensity for human error for the majority of pilot populations including those with English as a second language. Fourth, the results from the validation of theoretical models (")transfer(") showed that although cognitive load remained as a significant predictor of performance, both complexity and redundancy also had unique significant effects on performance. Furthermore, these results indicated that the relationship between these variables was not as (")clear-cut(") in the operational domain investigated here as the models from the domain of learning and instruction suggested. Until further research is conducted, (a) to investigate how changes in the operational task settings via adding additional coding (e.g., permanent record of clearances which can serve as both a memory aid and a way to verify a clearance is captured correctly) affect performance through mechanisms other than cognitive load; and (b) unless the theoretical models are modified to reflect how changes in the input variables impact the outcome in a variety of ways; a degree of prudence should be exercised when the results from the model (")transfer(") validation are applied to operational environments similar to the one investigated in this dissertation research.
Show less - Date Issued
- 2012
- Identifier
- CFE0004251, ucf:49504
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004251
