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Title: NONLINEAR ADAPTIVE ESTIMATION ANDITS APPLICATION TO SYNCHRONIZATION OF LORENZ SYSTEM.
Creator: Jin, Yufang, Qu, Zhihua, University of Central Florida
Abstract / Description: Synchronization and estimation of unknown constant parameters forLorenz-type transmitter are studied under the assumption that oneof the three state variables is not transmitted and thattransmitter parameters are not known apriori. An adaptivealgorithm is proposed to estimate both the state and systemparameters. Since Lorenz system shows the property of sensitivityto initial conditions and evolves in different mode with parametervariation, an equivalent system is introduced. The...
Show moreSynchronization and estimation of unknown constant parameters forLorenz-type transmitter are studied under the assumption that oneof the three state variables is not transmitted and thattransmitter parameters are not known apriori. An adaptivealgorithm is proposed to estimate both the state and systemparameters. Since Lorenz system shows the property of sensitivityto initial conditions and evolves in different mode with parametervariation, an equivalent system is introduced. The adaptiveobserver is designed based on this equivalent system without anyrequirement on initial conditions of the observer. It is shown byLyapunov arguments and persistent excitation analysis thatexponential stability of state and parameter estimation isguaranteed. Simulation results are included to demonstrateproperties of the algorithm. In a practical communication system,the received signals presented at the receiver part differ fromthose which were transmitted due to the effects of noise. Theproposed synchronization scheme is robust with regard to externalbounded disturbance. When an additive white gaussian noise (AWGN)channel model is considered, estimates of state and parameterconverge except for small errors. The results show promise ineither coherent detection or the message decoding intelecommunication systems.
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Date Issued: 2004
Identifier: CFE0000114, ucf:46187
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000114

Title: CHARACTERIZATION OF CRITICAL NETWORK COMPONENTS OF COUPLED OSCILLATORS.
Creator: Holifield, Gregory, A. S. Wu, A. Gonzalez,, University of Central Florida
Abstract / Description: This dissertation analyzes the fundamental limits for the determination of the network structure of loosely coupled oscillators based on observing the behavior of the network, specifically, node synchronization. The determination of the requisite characteristics and underlying behaviors necessary for the application of a theoretical mechanism for determining the underlying network topology in a network of loosely coupled natural oscillators are the desired outcome. To that end, this effort...
Show moreThis dissertation analyzes the fundamental limits for the determination of the network structure of loosely coupled oscillators based on observing the behavior of the network, specifically, node synchronization. The determination of the requisite characteristics and underlying behaviors necessary for the application of a theoretical mechanism for determining the underlying network topology in a network of loosely coupled natural oscillators are the desired outcome. To that end, this effort defines an analytical framework where key components of networks of coupled oscillators are isolated in order to determine the relationships between the various components. The relationship between the number of nodes in a network, the number of connections in the network, the number of connections of a given node, the distribution of the phases of the network, and the resolution of measurement of the components of the network, and system noise is investigated.
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Date Issued: 2006
Identifier: CFE0001452, ucf:47038
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001452

Title: DESIGN AND PERFORMANCE EVALUATION OF AN INTEGRATED MINIATURE SINGLE STAGE CENTRIFUGAL COMPRESSOR AND PERMANENT MAGNET SYNCHRONOUS MOTOR.
Creator: ACHARYA, DIPJYOTI, Kapat, Jayanta, University of Central Florida
Abstract / Description: An attempt has been made in this present work to design, fabricate and performance evaluate an integrated single stage centrifugal compressor and permanent magnet synchronous motor which is a key component of the reverse brayton cycle cryocooler. An off the shelf compressor – the driven and electric motor – the driver was not available commercially to suffice the requirements of the reverse brayton cryocooler. The integrated compressor-motor system was designed and tested with air...
Show moreAn attempt has been made in this present work to design, fabricate and performance evaluate an integrated single stage centrifugal compressor and permanent magnet synchronous motor which is a key component of the reverse brayton cycle cryocooler. An off the shelf compressor – the driven and electric motor – the driver was not available commercially to suffice the requirements of the reverse brayton cryocooler. The integrated compressor-motor system was designed and tested with air as the working fluid at mass flow rate of 7.3 grams per sec, with a compression ratio of 1.58 and driven by a 2 KW permanent magnet synchronous motor at a design speed of 108,000 rpm. A permanent magnet synchronous motor rotor was designed to operate to operate over 200,000 rpm at 77 Kelvin temperature. It involved iterative processes involving structural, thermal and rotordynamic analysis of the rotor. Selection of high speed ceramic ball bearings, their mounting, fit and pre-load played prominent role. Attempts were made to resolve misalignment issues for the compressor – motor system, which had severe impact on the rotordynamic performance of the system and therefore losses at high speeds , . A custom designed flexible coupler was designed and fabricated to run the compressor – motor system. An integrated compressor – motor system was an innovative design to resolve considerably several factors which hinder a high operational speed. Elimination of the coupler, reduction of number of bearings in the system and usage of fewer components on the rotor to increase the stiffness were distinct features of the integrated system. Several custom designed test-rigs were built which involved precision translation stages and angle brackets. Motor control software, an emulator, a DSP and a custom designed motor controller was assembled to run the motor. A cooling system was specially designed to cool the stator – rotor system. A pre-loading structure was fabricated to adequately pre-load the bearings. Flow measurement instruments such as mass flow meter, pressure transducers and thermocouples were used at several locations on the test rig to monitor the flow. An adjustable inlet guide vane was designed to control the tip clearance of the impeller.
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Date Issued: 2006
Identifier: CFE0001207, ucf:46955
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001207

Title: PHASE SYNCHRONIZATION IN THREE-DIMENSIONAL LATTICES AND GLOBALLY COUPLED POPULATIONS OF NONIDENTICAL ROSSLER OSCILLATORS.
Creator: Qi, Limin, Schober, Constance, University of Central Florida
Abstract / Description: A study on phase synchronization in large populations of nonlinear dynamical systems is presented in this thesis. Using the well-known Rossler system as a prototypical model, phase synchronization in one oscillator with periodic external forcing and in two-coupled nonidentical oscillators was explored at first. The study was further extended to consider three-dimensional lattices and globally coupled populations of nonidentical oscillators, in which the mathematical formulation that...
Show moreA study on phase synchronization in large populations of nonlinear dynamical systems is presented in this thesis. Using the well-known Rossler system as a prototypical model, phase synchronization in one oscillator with periodic external forcing and in two-coupled nonidentical oscillators was explored at first. The study was further extended to consider three-dimensional lattices and globally coupled populations of nonidentical oscillators, in which the mathematical formulation that represents phase synchronization in the generalized N-coupled Rossler system was derived and several computer programs that perform numerical simulations were developed. The results show the effects of coupling dimension, coupling strength, population size, and system parameter on phase synchronization of the various Rossler systems, which may be applicable to studying phase synchronization in other nonlinear dynamical systems as well.
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Date Issued: 2005
Identifier: CFE0000776, ucf:46559
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000776

Title: SYNCHRONIZATION IN ADVANCED OPTICAL COMMUNICATIONS.
Creator: Kim, Inwoong, Li, Guifang, University of Central Florida
Abstract / Description: All-optical synchronization and its application in advanced optical communications have been investigated in this dissertation. Dynamics of all-optical timing synchronization (clock recovery) using multi-section gain-coupled distributed-feedback (MS-GC DFB) lasers are discussed. A record speed of 180-GHz timing synchronization has been demonstrated using this device. An all-optical carrier synchronization (phase and polarization recovery) scheme from PSK (phase shift keying) data is proposed...
Show moreAll-optical synchronization and its application in advanced optical communications have been investigated in this dissertation. Dynamics of all-optical timing synchronization (clock recovery) using multi-section gain-coupled distributed-feedback (MS-GC DFB) lasers are discussed. A record speed of 180-GHz timing synchronization has been demonstrated using this device. An all-optical carrier synchronization (phase and polarization recovery) scheme from PSK (phase shift keying) data is proposed and demonstrated for the first time. As an application of all-optical synchronization, the characterization of advanced modulation formats using a linear optical sampling technique was studied. The full characterization of 10-Gb/s RZ-BPSK (return-to-zero binary PSK) data has been demonstrated. Fast lockup and walk-off of the all-optical timing synchronization process on the order of nanoseconds were measured in both simulation and experiment. Phase stability of the recovered clock from a pseudo-random bit sequence signal can be achieved by limiting the detuning between the frequency of free-running self-pulsation and the input bit rate. The simulation results show that all-optical clock recovery using TS-DFB lasers can maintain a better than 5 % clock phase stability for large variations in power, bit rate and optical carrier frequency of the input data and therefore is suitable for applications in ultrafast optical packet switching. All-optical timing synchronization of 180-Gb/s data streams has been demonstrated using a MS-GC DFB laser. The recovered clock has a jitter of less than 410 fs over a dynamic range of 7 dB. All-optical carrier synchronization from phase modulated data utilizes a phase sensitive oscillator (PSO), which used a phase sensitive amplifier (PSA) as a gain block. Furthermore, all-optical carrier synchronization from 10-Gb/s BPSK data was demonstrated in experiment. The PSA is configured as a nonlinear optical loop mirror (NOLM). A discrete linear system analysis was carried out to understand the stability of the PSO. Complex envelope measurement using coherent linear optical sampling with mode-locked sources is investigated. It is shown that reliable measurement of the phase requires that one of the optical modes of the sampling pulses be locked to the optical carrier of the data signal to be measured. Carrier-envelope offset (CEO) is found to have a negligible effect on the measurement. Measurement errors of the intensity profile and phase depend on the pulsewidth and chirp of the sampling pulses as well as the detuning between the carrier frequencies of the data signal and the center frequency of the sampling source. Characterization of the 10-Gb/s RZ-BPSK signal was demonstrated using the coherent detection technique. Measurements of the optical intensity profile, chirp and constellation diagram were demonstrated. A CW local oscillator was used and electrical sampling was performed using a sampling scope. A novel feedback scheme was used to stabilize homodyne detection.
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Date Issued: 2006
Identifier: CFE0001239, ucf:52894
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001239

Title: Virtual resistance based DC-link voltage regulation for Microgrid DG inverters.
Creator: Shinde, Siddhesh, Batarseh, Issa, Mikhael, Wasfy, Kutkut, Nasser, University of Central Florida
Abstract / Description: This research addresses the practical issues faced by Microgrid Distributed Generation (DG) inverters when operated in islanded mode. A Microgrid (MG) is an interconnection of domestic distributed loads and low voltage distributed energy sources such as micro-turbine, wind-turbine, PVs and storage devices. These energy sources are power limited in nature and constrain the operation of DG inverters to which they are coupled. DG inverters operated in islanded mode should maintain the power...
Show moreThis research addresses the practical issues faced by Microgrid Distributed Generation (DG) inverters when operated in islanded mode. A Microgrid (MG) is an interconnection of domestic distributed loads and low voltage distributed energy sources such as micro-turbine, wind-turbine, PVs and storage devices. These energy sources are power limited in nature and constrain the operation of DG inverters to which they are coupled. DG inverters operated in islanded mode should maintain the power balance between generation and demand. If DG inverter operating in islanded mode drains its source power below a certain limit or if it is incapable of supplying demanded power due to its hardware rating, it turns on its safety mechanism and isolates itself from the MG. This, in turn, increases the power demand on the rest of the DG units and can have a catastrophic impact on the viability of the entire system. This research presents a Virtual Resistance based DC Link Voltage Regulation technique which will allow DG inverters to continue to source their available power even when the power demand by the load is higher than their capacity without shutting off and isolating from the MG.
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Date Issued: 2016
Identifier: CFE0006503, ucf:51403
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006503

Title: Design of High-Efficiency Rare-Earth Permanent Magnet Synchronous Motor and Drive System.
Creator: Liu, Hanzhou, Wu, Thomas, Batarseh, Issa, Haralambous, Michael, Lin, Mingjie, Chow, Louis, University of Central Florida
Abstract / Description: Utilization of renewable energy has become the future trend in the trucking industry. Electrical power generated from renewable energy can replace part of the fuel usage. There is usually limited space for storing on-board battery. Thus, to better utilize the battery power, it becomes critical to have an efficient energy conversion device that can transfer energy from battery to amenities such as air conditioner, microwave, TV, mini refrigerator, etc. In this dissertation, a designed...
Show moreUtilization of renewable energy has become the future trend in the trucking industry. Electrical power generated from renewable energy can replace part of the fuel usage. There is usually limited space for storing on-board battery. Thus, to better utilize the battery power, it becomes critical to have an efficient energy conversion device that can transfer energy from battery to amenities such as air conditioner, microwave, TV, mini refrigerator, etc. In this dissertation, a designed permanent magnet synchronous motor (PMSM) can be such energy conversion device for an electric Auxiliary Power Unit (APU) application, which will have a desired output power of 2 kW at 2krpm, and maintain an efficiency greater than 90%. The design calls for good performance over a speed range of 1.5 krpm to 2.5 krpm. The current air conditioning system for automobile works only by (")on(") or (")off(") mode. For the heat mode, that means it is on with heat once the cabin temperature drops down to a level and off if the temperature rises back above that level. For the cool mode, that means it is on with cold air once the cabin temperature rises above a level, and off if the temperature drops back to that level. This is because the motor does not have the speed control functionality according to the temperature variation and people in the cabin do not feel much comfortable for that temperature change periodically as well as the inefficient energy consumption. With our novel technology, the designed motor can adjust its speed through the embedded system of our novel DC to AC inverter to provide a variable load. For example, with high efficiency, the fully charged battery sets (48 volts) can supply the electrical power and cooling to the cabin forabout 10 hours without recharging using the main engine.Copper loss is the most significant part of all the losses in low speed electric machines. Reducing the copper loss is the key to build highly efficient machine. We use copper wires with the current density lower than traditional design which result in large cross section of the wire and thus reduce the copper loss and improve the efficiency. This also makes thermal management easier and reduces the need to use active cooling methodologies (such as fan, liquid cooling or spray cooling); and hence the overall power density of the whole system (including cooling devices) will not decease much. In traditional machine design, the torque angle is designed to be in the rangeof 15 to 30 degrees at the rated power and speed. In our high efficiency motor design, we propose to use much lower torque angle of 2 to 15 degrees at the rated power and speed. Such design caneffectively increase the overload power handling capability and efficiency. Besides, small torque angle will result in large airgap size and increased thickness of the permanent magnets. Large airgap helps to reduce the windage loss of the machine and generates a lot less mechanical noise based on our design experience. Increased thickness of the permanent magnets helps to avoid thedemagnetization.As the technology of advanced micro-controller develops, fast response power electronic devices can be used in the motor controller. A novel design of DC to AC inverter with the fieldoriented control scheme and sliding mode observer algorithm for driving the designed motor is developed. The inverter has the capability of driving the motor with its output power at 2 kW.
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Date Issued: 2015
Identifier: CFE0006224, ucf:51064
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006224

Title: GLOBALLY-ASYNCHRONOUS, LOCALLY-SYNCHRONOUS WRAPPER CONFIGURATIONS FOR POINT-TO-POINT AND MULTI-POINT DATA COMMUNICATION.
Creator: Ravi, Akarsh, Yuan, Jiann, University of Central Florida
Abstract / Description: Globally-Asynchronous, Locally-Synchronous (GALS) design techniques employ the finer points of synchronous and asynchronous design methods to eliminate problems arising due to clock distribution, power dissipation, and large area over head. With the recent rise in the demand for System-on-a-Chip (SoC) designs, global clock distribution and power dissipation due to clock distribution are inevitable. In order to reduce/eliminate the effects of the global clock in synchronous designs and large...
Show moreGlobally-Asynchronous, Locally-Synchronous (GALS) design techniques employ the finer points of synchronous and asynchronous design methods to eliminate problems arising due to clock distribution, power dissipation, and large area over head. With the recent rise in the demand for System-on-a-Chip (SoC) designs, global clock distribution and power dissipation due to clock distribution are inevitable. In order to reduce/eliminate the effects of the global clock in synchronous designs and large area overhead in asynchronous designs, an alternative approach would be to utilize GALS design techniques. Not only do GALS designs eliminate the issue of using a global clock, they also have smaller area overhead when compared to purely asynchronous designs. Among the various GALS design approaches proposed till date, this thesis focuses on the working and implementation of Asynchronous Wrapper designs proposed by Muttersbach et al., in [1, 2]. This thesis specifically addresses different approaches to incorporate the wrappers in VLSI circuits, rather than discussing the efficiency and viability of GALS design techniques over purely synchronous or asynchronous approaches. It has been proven by researchers [3] that GALS design approaches bring down power consumption due to the elimination of the global clock by small amounts, but there is also a drop in performance. Since the goal of this thesis is to introduce the reader to GALS design techniques and not prove their efficiency, it is out of the scope of this thesis to validate the results shown in [3]. In our aim to introduce the reader to GALS design techniques, we first provide a comparison of synchronous and asynchronous design approaches, and then discuss the need for GALS design approaches. We will then address issues affecting GALS such as metastability, latency, flow control, and local clock alteration. After familiarizing the reader with the issues affecting GALS, we will then discuss various GALS design techniques proposed till date. We show the use of asynchronous FIFOs and asynchronous wrappers to realize GALS modules. Two wrapper design approaches are discussed: one being the asynchronous wrapper design proposed by Carlsson et al., in [4], and the other being the asynchronous wrapper design proposed in [1, 2]. An in-depth discussion and analysis of the wrapper design approach proposed in [1, 2] is provided based on the state transition graphs (STGs) that characterize the port-controller AFSMs. Various data transfer channel configurations that incorporate the wrapper port-controllers are designed and realized through VHDL codes, with their functioning verified through simulation results. Design examples showing the working of asynchronous wrappers to achieve point-to-point, synchronous-synchronous and synchronous-asynchronous data communication are provided. Finally, a design example to achieve multi-point data communication is realized. This example incorporates a previously proposed idea. We provide a modification to this idea by designing an arbiter that arbitrates between two separate requests coming into a multi-input port. Through the above design examples, the functionality and working of GALS asynchronous wrappers are verified, and recommendations for modifications are made to achieve flexible multi-point data communication.
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Date Issued: 2004
Identifier: CFE0000238, ucf:46245
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000238

Title: Synchronous Communication System for SAW Sensors Interrogation.
Creator: Troshin, Maxim, Malocha, Donald, Jones, W, Gong, Xun, University of Central Florida
Abstract / Description: During past two decades a variety of SAW based wireless sensors were invented and research is still in progress. As different frequencies, varied bandwidths, coding techniques and constantly changing post processing algorithms are being implemented, there is a constant need for a universal and adjustable synchronous communication system able to interrogate new generations of SAW sensors. This thesis presents the design of a multiple FPGA based communication system with an operational...
Show moreDuring past two decades a variety of SAW based wireless sensors were invented and research is still in progress. As different frequencies, varied bandwidths, coding techniques and constantly changing post processing algorithms are being implemented, there is a constant need for a universal and adjustable synchronous communication system able to interrogate new generations of SAW sensors. This thesis presents the design of a multiple FPGA based communication system with an operational frequency range of 450MHz-2.2GHz capable of producing user programmed modulated signal. The synchronous receiver is designed to have interchangeable chip, replacement of which would allow adjustment of the receiver's bandwidth. Within this paper the performance of the system is only evaluated at 915MHz centered 20MHz bandwidth region. An OFC temperature sensor was interrogated. Post-processing algorithms, measurement results, and proposals for the future use of the system are presented. Detailed overview of the structure and performance of every functional block along with design considerations are analyzed. Previously designed Matlab based software was adapted for post processing of the received signal. New software with simplified GUI was designed for programming of the desired signal.
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Date Issued: 2012
Identifier: CFE0004270, ucf:49543
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004270

Title: HIGHLY INTEGRATED DC-DC CONVERTERS.
Creator: Jia, Hongwei, Shen, Zhen, University of Central Florida
Abstract / Description: A monolithically integrated smart rectifier has been presented first in this work. The smart rectifier, which integrates a power MOSFET, gate driver and control circuitry, operates in a self-synchronized fashion based on its drain-source voltage, and does not need external control input. The analysis, simulation, and design considerations are described in detail. A 5V, 5-μm CMOS process was used to fabricate the prototype. Experimental results show that the proposed rectifier functions...
Show moreA monolithically integrated smart rectifier has been presented first in this work. The smart rectifier, which integrates a power MOSFET, gate driver and control circuitry, operates in a self-synchronized fashion based on its drain-source voltage, and does not need external control input. The analysis, simulation, and design considerations are described in detail. A 5V, 5-μm CMOS process was used to fabricate the prototype. Experimental results show that the proposed rectifier functions as expected in the design. Since no dead-time control needs to be used to switch the sync-FET and ctrl-FET, it is expected that the body diode losses can be reduced substantially, compared to the conventional synchronous rectifier. The proposed self-synchronized rectifier (SSR) can be operated at high frequencies and maintains high efficiency over a wide load range. As an example of the smart rectifierÃƒÂƒÃ‚Â‚ÃƒÂ‚Ã‚Â's application in isolated DC-DC converter, a synchronous flyback converter with SSR is analyzed, designed and tested. Experimental results show that the operating frequency could be as high as 4MHz and the efficiency could be improved by more than 10% compared to that when a hyper fast diode rectifier is used. Based on a new current-source gate driver scheme, an integrated gate driver for buck converter is also developed in this work by using a 0.35μm CMOS process with optional high voltage (50V) power MOSFET. The integrated gate driver consists both the current-source driver for high-side power MOSFET and low-power driver for low-side power iv MOSFET. Compared with the conventional gate driver circuit, the current-source gate driver can recovery some gate charging energy and reduce switching loss. So the current-source driver (CSD) can be used to improve the efficiency performance in high frequency power converters. This work also presents a new implementation of a power supply in package (PSiP) 5MHz buck converter, which is different from all the prior-of-art PSiP solutions by using a high-Q bondwire inductor. The high-Q bondwire inductor can be manufactured by applying ferrite epoxy to the common bondwire during standard IC packaging process, so the new implementation of PSiP is expected to be a cost-effective way of power supply integration.
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Date Issued: 2010
Identifier: CFE0003040, ucf:48354
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003040

Title: CONVENTIONAL AND ZVT SYNCHRONOUS BUCK CONVERTER DESIGN, ANALYSIS, AND MEASUREMENT.
Creator: Cory, Mark, Yuan, Jiann, University of Central Florida
Abstract / Description: The role played by power converting circuits is extremely important to almost any electronic system built today. Circuits that use converters of any type depend on power that is consistent in form and reliable in order to properly function. In addition, todayÃ‚Â's demands require more efficient use of energy, from large stationary systems such as power plants all the way down to small mobile devices such as laptops and cell phones. This places a need to reduce any losses...
Show moreThe role played by power converting circuits is extremely important to almost any electronic system built today. Circuits that use converters of any type depend on power that is consistent in form and reliable in order to properly function. In addition, todayÃ‚Â's demands require more efficient use of energy, from large stationary systems such as power plants all the way down to small mobile devices such as laptops and cell phones. This places a need to reduce any losses to a minimum. The power conversion circuitry in a system is a very good place to reduce a large amount of unnecessary loss. This can be done using circuit topologies that are low loss in nature. For low loss and high performance, soft switching topologies have offered solutions in some cases. Also, limited study has been performed on device aging effects on switching mode power converting circuits. The impact of this effect on a converterÃ‚Â's overall efficiency is theoretically known but with little experimental evidence in support. In this thesis, non-isolated buck type switching converters will be the main focus. This type of power conversion is widely used in many systems for DC to DC voltage step down. Newer methods and topologies to raise converter power efficiency are discussed, including a new synchronous ZVT topology . Also, a study has been performed on device aging effects on converter efficiency. Various scenarios of voltage conversion, switching frequency, and circuit components as well as other conditions have been considered. Experimental testing has been performed in both cases, ZVTÃ‚Â's benefits and device aging effects, the results of which are discussed as well.
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Date Issued: 2010
Identifier: CFE0003106, ucf:48650
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003106

Title: Team Interaction Dynamics during Collaborative Problem Solving.
Creator: Wiltshire, Travis, Fiore, Stephen, Jentsch, Florian, Salas, Eduardo, Wiegand, Rudolf, University of Central Florida
Abstract / Description: This dissertation contributes an enhanced understanding of team cognition, in general, and collaborative problem solving (CPS), specifically, through an integration of methods that measure team interaction dynamics and knowledge building as it occurs during a complex CPS task. The need for better understanding CPS has risen in prominence as many organizations have increasingly worked to address complex problems requiring the combination of diverse sets of individual expertise to achieve...
Show moreThis dissertation contributes an enhanced understanding of team cognition, in general, and collaborative problem solving (CPS), specifically, through an integration of methods that measure team interaction dynamics and knowledge building as it occurs during a complex CPS task. The need for better understanding CPS has risen in prominence as many organizations have increasingly worked to address complex problems requiring the combination of diverse sets of individual expertise to achieve solutions for novel problems. Towards this end, the present research drew from theoretical and empirical work on Macrocognition in Teams that describes the knowledge coordination arising from team communications during CPS. It built from this by incorporating the study of team interaction during complex collaborative cognition. Interaction between team members in such contexts has proven to be inherently dynamic and exhibiting nonlinear patterns not accounted for by extant research methods. To redress this gap, the present research drew from work in cognitive science designed to study social and team interaction as a nonlinear dynamical system. CPS was examined by studying knowledge building and interaction processes of 43 dyads working on NASA's Moonbase Alpha simulation, a CPS task. Both non-verbal and verbal interaction dynamics were examined. Specifically, frame-differencing, an automated video analysis technique, was used to capture the bodily movements of participants and content coding was applied to the teams' communications to characterize their CPS processes. A combination of linear (i.e., multiple regression, t-test, and time-lagged cross-correlation analysis), as well as nonlinear analytic techniques (i.e., recurrence quantification analysis; RQA) were applied. In terms of the predicted interaction dynamics, it was hypothesized that teams would exhibit synchronization in their bodily movements and complementarity in their communications and further, that teams more strongly exhibiting these forms of coordination will produce better problem solving outcomes. Results showed that teams did exhibit a pattern of bodily movements that could be characterized as synchronized, but higher synchronization was not systematically related to performance. Further, results showed that teams did exhibit communicative interaction that was complementary, but this was not predictive of better problem solving performance. Several exploratory research questions were proposed as a way of refining the application of these techniques to the investigation of CPS. Results showed that semantic code-based communications time-series and %REC and ENTROPY recurrence-based measures were most sensitive to differences in performance. Overall, this dissertation adds to the scientific body of knowledge by advancing theory and empirical knowledge on the forms of verbal and non-verbal team interaction during CPS, but future work remains to be conducted to identify the relationship between interaction dynamics and CPS performance.
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Date Issued: 2015
Identifier: CFE0005907, ucf:50867
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005907

Title: On the Capillary Electrophoresis of Monohydroxy Metabolites of Polycyclic Aromatic Hydrocarbons and its Application to the Analysis of Biological Matrices.
Creator: Knobel, Gaston, Campiglia, Andres, Clausen, Christian, Belfield, Kevin, Liao, Yi, Bhattacharya, Aniket, University of Central Florida
Abstract / Description: Polycyclic aromatic hydrocarbons (PAH) are a class of environmental pollutants consisting of a minimum of two fused aromatics rings originating from the incomplete combustion of organic matter and/or anthropogenic sources. Numerous possible anthropogenic and natural sources make the presence of PAH ubiquitous in the environment. The carcinogenic nature of some PAH and their ubiquitous presence makes their chemical analysis a topic of environmental and toxicological importance. Although...
Show morePolycyclic aromatic hydrocarbons (PAH) are a class of environmental pollutants consisting of a minimum of two fused aromatics rings originating from the incomplete combustion of organic matter and/or anthropogenic sources. Numerous possible anthropogenic and natural sources make the presence of PAH ubiquitous in the environment. The carcinogenic nature of some PAH and their ubiquitous presence makes their chemical analysis a topic of environmental and toxicological importance. Although environmental monitoring of PAH is an important step to prevent exposure to contaminated sites, it provides little information on the actual uptake and subsequent risks. Parent PAH are relatively inert and need metabolic activation to express their carcinogenicity. Covalent binding to DNA appears to be the first critical step in the initiation of the tumor formation process.To this end, the determination of short term biomarkers (-) such as monohydroxy-PAH metabolites (OH-PAH) - fills an important niche to interpret actual PAH exposure levels, prevent extreme body burdens and minimize cancer risk. One would certainly prefer an early warning parameter over a toxicological endpoint (-) such as DNA-adducts (-) indicating that extensive damage has already been done. Several methods have been developed to determine OH-PAH in specific tissue or excreta and food samples. The general trend for the analysis of OH-PAH follows the pattern of sample collection, sample clean-up and pre-concentration, chromatographic separation and quantification. Popular approaches for sample clean-up and pre-concentration include liquid-liquid extraction (LLE) and solid-phase extraction (SPE). Chromatographic separation and quantification has been based on high-performance liquid chromatography-room temperature fluorescence detection (HPLC) and gas chromatography-mass spectrometry (GC-MS).Although chromatographic techniques provide reliable results in the analysis of OH-PAH, their experimental procedures are time consuming and expensive. Elution times of 30-60 minutes are typical and standards must be run periodically to verify retention times. If the concentrations of target species are found to lie outside the detector's response range, the sample must be diluted and the process repeated. On the other end of the concentration range, many samples are (")zeroes,(") i.e. the concentrations are below detection limits. Additional problems arise when laboratory procedures are scaled up to handle thousands of samples under mass screening conditions. Under the prospective of a sustainable environment, the large usage of organic solvents is one of the main limitations of the current chromatographic methodology.This dissertation focuses on the development of a screening methodology for the analysis of OH-PAH in urine and milk samples. Screening techniques capable of providing a (")yes or no(") answer to OH-PAH contamination prevent unnecessary scrutiny of un-contaminated samples via conventional methods, reduce analysis cost and expedite the turnaround time for decision making purposes. The proposed methodology is based on capillary zone electrophoresis (CZE) and synchronous fluorescence spectroscopy (SFS). Metabolites extraction and pre-concentration is achieved with optimized SPE, LLE and/or QuEChERS (quick, easy, cheap, effective, rugged and safe) procedures. The small sample and extracting solvent volumes facilitate the simultaneous extraction of numerous samples via an environmentally friendly procedure, which is well-suited for routine monitoring of numerous samples. Sample stacking is successfully implemented to improve CZE limits of detection by two orders of magnitude. The unique electrophoretic pattern of positional isomers of OH-PAH demonstrates the potential of CZE for the unambiguous determination of metabolites with similar chromatographic behaviors and virtually similar fragmentation patterns. The direct determination of OH-PAH without chromatographic separation is demonstrated via SFS. The non-destructive nature of SFS provides ample opportunity for further metabolite confirmation via chromatographic techniques.
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Date Issued: 2013
Identifier: CFE0005102, ucf:50761
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005102

Title: Optimal Switch Timing for Piezoelectric-Based Semi-Active Vibration Reduction Techniques.
Creator: Kelley, Christopher, Kauffman, Jeffrey, Das, Tuhin, Xu, Yunjun, University of Central Florida
Abstract / Description: Semi-active vibration reduction techniques switch a piezoelectric transducer between an open circuit and a shunt circuit in a way that reduces vibration. The steady-state vibration amplitude is reduced by exploiting the change in stiffness between states, manipulating the converted electrical energy, or both. Semi-active techniques typically require four switches per vibration cycle. Control laws such as state switching and synchronized switch damping require switches to occur at every...
Show moreSemi-active vibration reduction techniques switch a piezoelectric transducer between an open circuit and a shunt circuit in a way that reduces vibration. The steady-state vibration amplitude is reduced by exploiting the change in stiffness between states, manipulating the converted electrical energy, or both. Semi-active techniques typically require four switches per vibration cycle. Control laws such as state switching and synchronized switch damping require switches to occur at every displacement extrema. Due to the complexity of analyzing a system with discrete switches, these control laws were developed based on intuition. The few analyses that attempt to determine an optimal switching law mathematically only evaluate the system at resonance. This thesis investigates the effects of switch timing on vibration reduction and the frequency dependence of the optimal switch timing control law. Regardless of the switch timing, sensing uncertainties, noise, and modeling errors can cause the switches to occur away from the designed moment. Thus, this work also quantifies the expected degradation in vibration reduction performance due to variations in the designed switch time. Experimental, numerical, and analytical solutions agree that the optimal switch timing of these semi-active techniques depends on frequency. A closed-form solution for the optimal switch timing is derived in terms of well-known, non-dimensional parameters.
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Date Issued: 2016
Identifier: CFE0006336, ucf:51555
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006336

Title: DESIGN OF HIGH EFFICIENCY BRUSHLESS PERMANENT MAGNET MACHINES AND DRIVER SYSTEM.
Creator: He, Chengyuan, Wei, Lei, Sundaram, Kalpathy, Zhou, Qun, Jin, Yier, Zou, Shengli, University of Central Florida
Abstract / Description: The dissertation is concerned with the design of high-efficiency permanent magnet synchronous machinery and the control system. The dissertation first talks about the basic concept of the permanent magnet synchronous motor (PMSM) design and the mathematics design model of the advanced design method. The advantage of the design method is that it can increase the high load capacity at no cost of increasing the total machine size. After that, the control method of the PMSM and Permanent magnet...
Show moreThe dissertation is concerned with the design of high-efficiency permanent magnet synchronous machinery and the control system. The dissertation first talks about the basic concept of the permanent magnet synchronous motor (PMSM) design and the mathematics design model of the advanced design method. The advantage of the design method is that it can increase the high load capacity at no cost of increasing the total machine size. After that, the control method of the PMSM and Permanent magnet synchronous generator (PMSG) is introduced. The design, simulation, and test of a permanent magnet brushless DC (BLDC) motor for electric impact wrench and new mechanical structure are first presented based on the design method. Finite element analysis based on the Maxwell 2D is built to optimize the design and the control board is designed using Altium Designer. Both the motor and control board have been fabricated and tested to verify the design. The electrical and mechanical design are combined, and it provides an analytical IPMBLDC design method and an innovative and reasonable mechanical dynamical calculation method for the impact wrench system, which can be used in whole system design of other functional electric tools. A 2kw high-efficiency alternator system and its control board system are also designed, analyzed and fabricated applying to the truck auxiliary power unit (APU). The alternator system has two stages. The first stage is that the alternator three-phase outputs are connected to the three-phase active rectifier to get 48V DC. An advanced Sliding Mode Observer (SMO) is used to get an alternator position. The buck is used for the second stage to get 14V DC output. The whole system efficiency is much higher than the traditional system using induction motor.
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Date Issued: 2018
Identifier: CFE0007334, ucf:52135
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007334

Title: The Effects of Synchronous Online Cognitive Strategy Instruction in Writing for Students with Learning Disabilities.
Creator: Straub, Carrie, Vasquez, Eleazar, Wienke, Wilfred, Dieker, Lisa, Kaplan, Jeffrey, University of Central Florida
Abstract / Description: This study investigates the effects of self-regulated strategy development (Harris, Graham, (&) Mason, 2009) for cognitive strategy instruction in persuasive writing (POW+TREE) using a synchronous online learning environment for special education students. Participants are four adolescent students with learning disabilities (LD) with low achievement in writing. One undergraduate research assistant delivered instruction using a synchronous online platform (e.g., Adobe Connect) in conjunction...
Show moreThis study investigates the effects of self-regulated strategy development (Harris, Graham, (&) Mason, 2009) for cognitive strategy instruction in persuasive writing (POW+TREE) using a synchronous online learning environment for special education students. Participants are four adolescent students with learning disabilities (LD) with low achievement in writing. One undergraduate research assistant delivered instruction using a synchronous online platform (e.g., Adobe Connect) in conjunction with collaborative writing software (e.g., Google Docs word processing). A multiple probe across participants design was used to demonstrate a functional relationship between instruction and number of essay elements (EE). Number of correct minus incorrect word sequences (CIWS) was used as a secondary dependent measure. A non-experimental pre-post design was used to compare the mean performance of holistic writing quality scores and standard scores from the TOWL-3. All four participants gained EE and CIWS from baseline to treatment and demonstrated standard score changes from pre to post-test on the TOWL-3. Implications for writing instruction for students with LD using online learning environments are discussed.
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Date Issued: 2012
Identifier: CFE0004606, ucf:49937
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004606

Title: ANALYSIS OF TIME SYNCHRONIZATION ERRORS IN HIGH DATA RATE ULTRAWIDEBAND ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING DATA LINKS.
Creator: Bates, Lakesha, Jones, W. Linwood, University of Central Florida
Abstract / Description: Emerging Ultra Wideband (UWB) Orthogonal Frequency Division Multiplexing (OFDM) systems hold the promise of delivering wireless data at high speeds, exceeding hundreds of megabits per second over typical distances of 10 meters or less. The purpose of this Thesis is to estimate the timing accuracies required with such systems in order to achieve Bit Error Rates (BER) of the order of magnitude of 10-12 and thereby avoid overloading the correction of irreducible errors due to misaligned timing...
Show moreEmerging Ultra Wideband (UWB) Orthogonal Frequency Division Multiplexing (OFDM) systems hold the promise of delivering wireless data at high speeds, exceeding hundreds of megabits per second over typical distances of 10 meters or less. The purpose of this Thesis is to estimate the timing accuracies required with such systems in order to achieve Bit Error Rates (BER) of the order of magnitude of 10-12 and thereby avoid overloading the correction of irreducible errors due to misaligned timing errors to a small absolute number of bits in error in real-time relative to a data rate of hundreds of megabits per second. Our research approach involves managing bit error rates through identifying maximum timing synchronization errors. Thus, it became our research goal to determine the timing accuracies required to avoid operation of communication systems within the asymptotic region of BER flaring at low BERs in the resultant BER curves. We propose pushing physical layer bit error rates to below 10-12 before using forward error correction (FEC) codes. This way, the maximum reserve is maintained for the FEC hardware to correct for burst as well as recurring bit errors due to corrupt bits caused by other than timing synchronization errors.
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Date Issued: 2004
Identifier: CFE0000197, ucf:46173
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000197

Title: Stability and Control in Complex Networks of Dynamical Systems.
Creator: Manaffam, Saeed, Vosoughi, Azadeh, Behal, Aman, Atia, George, Rahnavard, Nazanin, Javidi, Tara, Das, Tuhin, University of Central Florida
Abstract / Description: Stability analysis of networked dynamical systems has been of interest in many disciplines such as biology and physics and chemistry with applications such as LASER cooling and plasma stability. These large networks are often modeled to have a completely random (Erd\"os-R\'enyi) or semi-random (Small-World) topologies. The former model is often used due to mathematical tractability while the latter has been shown to be a better model for most real life networks.The recent emergence of cyber...
Show moreStability analysis of networked dynamical systems has been of interest in many disciplines such as biology and physics and chemistry with applications such as LASER cooling and plasma stability. These large networks are often modeled to have a completely random (Erd\"os-R\'enyi) or semi-random (Small-World) topologies. The former model is often used due to mathematical tractability while the latter has been shown to be a better model for most real life networks.The recent emergence of cyber physical systems, and in particular the smart grid, has given rise to a number of engineering questions regarding the control and optimization of such networks. Some of the these questions are: \emph{How can the stability of a random network be characterized in probabilistic terms? Can the effects of network topology and system dynamics be separated? What does it take to control a large random network? Can decentralized (pinning) control be effective? If not, how large does the control network needs to be? How can decentralized or distributed controllers be designed? How the size of control network would scale with the size of networked system?}Motivated by these questions, we began by studying the probability of stability of synchronization in random networks of oscillators. We developed a stability condition separating the effects of topology and node dynamics and evaluated bounds on the probability of stability for both Erd\"os-R\'enyi (ER) and Small-World (SW) network topology models. We then turned our attention to the more realistic scenario where the dynamics of the nodes and couplings are mismatched. Utilizing the concept of $\varepsilon$-synchronization, we have studied the probability of synchronization and showed that the synchronization error, $\varepsilon$, can be arbitrarily reduced using linear controllers.We have also considered the decentralized approach of pinning control to ensure stability in such complex networks. In the pinning method, decentralized controllers are used to control a fraction of the nodes in the network. This is different from traditional decentralized approaches where all the nodes have their own controllers. While the problem of selecting the minimum number of pinning nodes is known to be NP-hard and grows exponentially with the number of nodes in the network we have devised a suboptimal algorithm to select the pinning nodes which converges linearly with network size. We have also analyzed the effectiveness of the pinning approach for the synchronization of oscillators in the networks with fast switching, where the network links disconnect and reconnect quickly relative to the node dynamics.To address the scaling problem in the design of distributed control networks, we have employed a random control network to stabilize a random plant network. Our results show that for an ER plant network, the control network needs to grow linearly with the size of the plant network.
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Date Issued: 2015
Identifier: CFE0005834, ucf:50902
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005834

Title: Modeling and Simulation of All-electric Aircraft Power Generation and Actuation.
Creator: Woodburn, David, Wu, Xinzhang, Batarseh, Issa, Georgiopoulos, Michael, Haralambous, Michael, Chow, Louis, University of Central Florida
Abstract / Description: Modern aircraft, military and commercial, rely extensively on hydraulic systems. However, there is great interest in the avionics community to replace hydraulic systems with electric systems. There are physical challenges to replacing hydraulic actuators with electromechanical actuators (EMAs), especially for flight control surface actuation. These include dynamic heat generation and power management.Simulation is seen as a powerful tool in making the transition to all-electric aircraft by...
Show moreModern aircraft, military and commercial, rely extensively on hydraulic systems. However, there is great interest in the avionics community to replace hydraulic systems with electric systems. There are physical challenges to replacing hydraulic actuators with electromechanical actuators (EMAs), especially for flight control surface actuation. These include dynamic heat generation and power management.Simulation is seen as a powerful tool in making the transition to all-electric aircraft by predicting the dynamic heat generated and the power flow in the EMA. Chapter 2 of this dissertation describes the nonlinear, lumped-element, integrated modeling of a permanent magnet (PM) motor used in an EMA. This model is capable of representing transient dynamics of an EMA, mechanically, electrically, and thermally.Inductance is a primary parameter that links the electrical and mechanical domains and, therefore, is of critical importance to the modeling of the whole EMA. In the dynamic mode of operation of an EMA, the inductances are quite nonlinear. Chapter 3 details the careful analysis of the inductances from finite element software and the mathematical modeling of these inductances for use in the overall EMA model.Chapter 4 covers the design and verification of a nonlinear, transient simulation model of a two-step synchronous generator with three-phase rectifiers. Simulation results are shown.
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Date Issued: 2013
Identifier: CFE0005074, ucf:49975
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005074

Title: Improvements on Instrumentation to Explore the Multidimensionality of Luminescence Spectroscopy.
Creator: Moore, Anthony, Campiglia, Andres, Chumbimuni Torres, Karin, Harper, James, Rex, Matthew, Lee, Woo Hyoung, University of Central Florida
Abstract / Description: This dissertation presents experimental and instrumentation developments that take full advantage of the multidimensional nature of line narrowing spectroscopy at liquid nitrogen (77 K) and liquid helium (4.2 K) temperatures. The inconvenience of sample freezing procedures is eliminated with the aid of cryogenic fiber optic probes. Rapid collection of multidimensional data formats such as wavelength time matrices, excitation emission matrices, time-resolved excitation emission matrices and...
Show moreThis dissertation presents experimental and instrumentation developments that take full advantage of the multidimensional nature of line narrowing spectroscopy at liquid nitrogen (77 K) and liquid helium (4.2 K) temperatures. The inconvenience of sample freezing procedures is eliminated with the aid of cryogenic fiber optic probes. Rapid collection of multidimensional data formats such as wavelength time matrices, excitation emission matrices, time-resolved excitation emission matrices and time resolved excitation emission cubes is made possible with the combination of a pulsed tunable dye laser, a spectrograph and an intensifier-charged coupled device. These data formats provide unique opportunities for processing vibrational luminescence data with second order multivariate calibration algorithms. The use of cryogenic fiber optic probes is extended to commercial instrumentation. An attractive feature of spectrofluorimeters with excitation and emission monochromators is the possibility to record synchronous spectra. The advantages of this approach, which include narrowing of spectral bandwidth and simplification of emission spectra, were demonstrated with the direct analysis of highly toxic dibenzopyrene isomers. The same is true for the collection of steady-state fluorescence excitation-emission matrices. These approaches provide a general solution to unpredictable spectral interference, a ubiquitous problem for the analysis of organic pollutants in environmental samples of unknown composition. Since commercial spectrofluorimeters are readily available in most academic institutions, industrial settings and research institutes, the developments presented here should facilitate the widespread application of line-narrowing spectroscopic techniques to the direct determination, no chromatographic separation, of highly toxic compounds in complex environmental matrixes of unknown composition.
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Date Issued: 2015
Identifier: CFE0005847, ucf:50934
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005847

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