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Title: Spray_Deposited Titanium-Oxide Films For Infrared Optics, Photonics, And Solar Cell Applications.
Creator: Alhasan, Sarmad, Peale, Robert, Sundaram, Kalpathy, Mikhael, Wasfy, Abdolvand, Reza, Kar, Aravinda, University of Central Florida
Abstract / Description: Self-assembled TiO2 foam-like films, were grown by the water based Streaming Process for ElectrodelessElectrochemical Deposition (SPEED). The morphology of the 1 m thick films consistsof a tangled ropy structure with individual strands of 200 nm diameter and open pores of 0.1to 3 micron dimensions. Such films are advantageous for proposed perovskite solar cell comprisingCH3NH3PbI3 absorber with additional inorganic films as contact and conduction layers,all deposited by SPEED. Lateral film...
Show moreSelf-assembled TiO2 foam-like films, were grown by the water based Streaming Process for ElectrodelessElectrochemical Deposition (SPEED). The morphology of the 1 m thick films consistsof a tangled ropy structure with individual strands of 200 nm diameter and open pores of 0.1to 3 micron dimensions. Such films are advantageous for proposed perovskite solar cell comprisingCH3NH3PbI3 absorber with additional inorganic films as contact and conduction layers,all deposited by SPEED. Lateral film resistivity is in the range 20 - 200 k-cm, increasing withgrowth temperature, while sheet resistance is in the range 2 ?? 20 108 /Sq. Xray diffractionconfirms presence of TiO2 crystals of orthorhombic class (Brookite). UV-vis spectroscopy showshigh transmission below the expected 3.2 eV TiO2 bandgap. Transmittance increases with growthtemperature. This is a Ropy TiO2 thin film.We also prepared a Smooth TiO2 thin film. Self-assembled TiO2 film deposited by aqueous-spraydeposition was investigated to evaluate morphology, crystalline phase, and infrared optical constants.The Anatase nano-crystalline film had 10 nm characteristic surface roughness sparselypunctuated by defects of not more than 200 nm amplitude. The film is highly transparent throughoutthe visible to wavelengths of 12 m. The indirect band gap was determined to be 3.2 eV. Importantfor long-wave infrared applications is that dispersion in this region is weak compared with themore commonly used dielectic SiO2 for planar structures. The low-cost, large-area, atmosphericpressure,chemical spray deposition method allows conformal fabrication on flexible substrates forlong-wave infrared photonics.For comparison TiO2 films deposited by electron-beam evaporation were evaluated to determinemorphology, crystalline phase, and optical transparency.The evaporated TiO2 film was amorphous but crystallized into Anatase phase after annealing.Such film is attractive as electron conductor of unprecedented thinness and flexibility for proposedperovskite solar cell comprising CH3NH3PbI3 absorber with additional inorganic films as contactand conduction layers. The spray deposition method would allow conformal solar cell fabricationon flexible substrates for wearable power generation. Band gap of Evaporated TiO2 film is 4.0 eV.We prepared BaTiO3 thin film to know infrared pyroelectric response.Self-assembled nano-crystalline BaTiO3 films on stainless steel foil substrates, were grown by thewater based Streaming Process for Electrodeless Electrochemical Deposition (SPEED). SPEED isan aqueous process that deposits self-assembled nano-crystalline inorganic thin films over largeareas, without a vacuum, providing a scalable and manufacturing friendly process to fabricatedurable films. The morphology of the 1m thick films comprises single crystals of micron dimensionsimbedded in a matrix of nanocrystals. XRD confirms presence of BaTiO3 crystals ofhexagonal phase for samples annealed at 500C. Subsequent annealing at 600C transforms thefilm to the cubic phase. Potential applications include dielectric layers, capacitors, waveguides,ferroelectric RAM, pyroelectric infrared detectors, and phosphors. Characterization of infraredpyroelectric response at 10m wavelength shows an initially good sensitivity that reversibly decaysover a period of days due to water vapor absorption. A short-lived photo-response due topoling of the hydrated sample is also observed. We studied BaTiO3 to know hysteresis loop.Pyroelectric photoresponse of aqueous spray deposited thin films containing BaTiO3 nano-crystalsis reported. X-ray diffraction data indicate the presence of hexagonal BaTiO3 nano-crystals with20 nm crystalline domains in a matrix of some as yet unidentified nano-crystalline material.When the film is annealed at 600C, the X-ray pattern changes significantly and indicates a conversionto one of the non-hexagonal phases of BaTiO3 as well as a complete change in the matrix.With suitable amplifier, the measured photoresponse was 40V/W.Ferroelectric hysteresis on a film with significant presence of hexagonal BaTiO3 shows saturatedpolarization which is about 5-times smaller than for the bulk tetragonal phase.
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Date Issued: 2017
Identifier: CFE0006710, ucf:51899
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006710

Title: Method for Real-Time Signal Selection for Passive Coherent Location Systems.
Creator: Johnson, Nicholas, Jones, W Linwood, Gong, Xun, Mikhael, Wasfy, Rockway, John, Lichtenberg, Christopher, University of Central Florida
Abstract / Description: Passive coherent location (PCL) systems use signals of opportunity to perform traditional radar detection, targeting, and tracking functions. Traditionally these signals include FM radio, digital TV, GSM, and GPS because of their availability in most urban environments. A benefit of having an abundance of signals is the ability to choose which of those best meet the desired system intentions. For example, one may want to choose a digital TV signal over an FM radio signal due to its range...
Show morePassive coherent location (PCL) systems use signals of opportunity to perform traditional radar detection, targeting, and tracking functions. Traditionally these signals include FM radio, digital TV, GSM, and GPS because of their availability in most urban environments. A benefit of having an abundance of signals is the ability to choose which of those best meet the desired system intentions. For example, one may want to choose a digital TV signal over an FM radio signal due to its range resolution characteristics. This work presents a novel algorithm for characterizing commercial signals for use in a PCL system. By analyzing each signal's ambiguity function in terms of amplitude, transmitter geometry, range and Doppler resolution, and sidelobe levels, a comparative evaluation can be made to decide which signals are best suited for an intended radar function. In addition, this research shows that multiple signals can be combined in the detection process to increase the probability of detection over that of a single signal. Finally, this research investigates the geometric considerations for PCL systems in terms of bistatic radar geometry. The results show zones of linear and non-linear relationships between time delay, range, and Doppler frequency.
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Date Issued: 2017
Identifier: CFE0007123, ucf:51964
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007123

Title: Robust, Scalable, and Provable Approaches to High Dimensional Unsupervised Learning.
Creator: Rahmani, Mostafa, Atia, George, Vosoughi, Azadeh, Mikhael, Wasfy, Nashed, M, Pensky, Marianna, University of Central Florida
Abstract / Description: This doctoral thesis focuses on three popular unsupervised learning problems: subspace clustering, robust PCA, and column sampling. For the subspace clustering problem, a new transformative idea is presented. The proposed approach, termed Innovation Pursuit, is a new geometrical solution to the subspace clustering problem whereby subspaces are identified based on their relative novelties. A detailed mathematical analysis is provided establishing sufficient conditions for the proposed method...
Show moreThis doctoral thesis focuses on three popular unsupervised learning problems: subspace clustering, robust PCA, and column sampling. For the subspace clustering problem, a new transformative idea is presented. The proposed approach, termed Innovation Pursuit, is a new geometrical solution to the subspace clustering problem whereby subspaces are identified based on their relative novelties. A detailed mathematical analysis is provided establishing sufficient conditions for the proposed method to correctly cluster the data points. The numerical simulations with both real and synthetic data demonstrate that Innovation Pursuit notably outperforms the state-of-the-art subspace clustering algorithms. For the robust PCA problem, we focus on both the outlier detection and the matrix decomposition problems. For the outlier detection problem, we present a new algorithm, termed Coherence Pursuit, in addition to two scalable randomized frameworks for the implementation of outlier detection algorithms. The Coherence Pursuit method is the first provable and non-iterative robust PCA method which is provably robust to both unstructured and structured outliers. Coherence Pursuit is remarkably simple and it notably outperforms the existing methods in dealing with structured outliers. In the proposed randomized designs, we leverage the low dimensional structure of the low rank component to apply the robust PCA algorithm to a random sketch of the data as opposed to the full scale data. Importantly, it is analytically shown that the presented randomized designs can make the computation or sample complexity of the low rank matrix recovery algorithm independent of the size of the data. At the end, we focus on the column sampling problem. A new sampling tool, dubbed Spatial Random Sampling, is presented which performs the random sampling in the spatial domain. The most compelling feature of Spatial Random Sampling is that it is the first unsupervised column sampling method which preserves the spatial distribution of the data.
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Date Issued: 2018
Identifier: CFE0007083, ucf:52010
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007083

Title: Design and Implementation of PV-Firming and Optimization Algorithms For Three-Port Microinverters.
Creator: Alharbi, Mahmood, Batarseh, Issa, Haralambous, Michael, Mikhael, Wasfy, Yuan, Jiann-Shiun, Kutkut, Nasser, University of Central Florida
Abstract / Description: With the demand increase for electricity, the ever-increasing awareness of environmental issues, coupled with rolling blackouts, the role of renewable energy generation is increasing along with the thirst for electricity and awareness of environmental issues. This dissertation proposes the design and implementation of PV-firming and optimization algorithms for three-port microinverters.Novel strategies are proposed in Chapters 3 and 4 for harvesting stable solar power in spite of intermittent...
Show moreWith the demand increase for electricity, the ever-increasing awareness of environmental issues, coupled with rolling blackouts, the role of renewable energy generation is increasing along with the thirst for electricity and awareness of environmental issues. This dissertation proposes the design and implementation of PV-firming and optimization algorithms for three-port microinverters.Novel strategies are proposed in Chapters 3 and 4 for harvesting stable solar power in spite of intermittent solar irradiance. PV firming is implemented using a panel-level three-port grid-tied PV microinverter system instead of the traditional high-power energy storage and management system at the utility scale. The microinverter system consists of a flyback converter and an H-bridge inverter/rectifier, with a battery connected to the DC-link. The key to these strategies lies in using static and dynamic algorithms to generate a smooth PV reference power. The outcomes are applied to various control methods to charge/discharge the battery so that a stable power generation profile is obtained. In addition, frequency-based optimization for the inverter stage is presented.One of the design parameters of grid-tied single-phase H-bridge sinusoidal pulse-width modulation (SPWM) microinverters is switching frequency. The selection of the switching frequency is a tradeoff between improving the power quality by reducing the total harmonic distortion (THD), and improving the efficiency by reducing the switching loss. In Chapter 5, two algorithms are proposed for optimizing both the power quality and the efficiency of the microinverter. They do this by using a frequency tracking technique that requires no hardware modification. The first algorithm tracks the optimal switching frequency for maximum efficiency at a given THD value. The second maximizes the power quality of the H-bridge micro-inverter by tracking the switching frequency that corresponds to the minimum THD.Real-time PV intermittency and usable capacity data were evaluated and then further analyzed in MATLAB/SIMULINK to validate the PV firming control. The proposed PV firming and optimization algorithms were experimentally verified, and the results evaluated. Finally, Chapter 6 provides a summary of key conclusions and future work to optimize the presented topology and algorithms.
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Date Issued: 2018
Identifier: CFE0007305, ucf:52166
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007305

Title: MONOLITHICALLY INTEGRATED WAVELENGTH TUNABLE LASER DIODE FOR INTEGRATED OPTIC SURFACE PLASMON RESONANCE SENSING.
Creator: Tabbakh, Thamer, Likamwa, Patrick, Batarseh, Issa, Fathpour, Sasan, Mikhael, Wasfy, Khajavikhan, Mercedeh, University of Central Florida
Abstract / Description: In this work, we demonstrate an InGaAsP multiple quantum well tunable laser diode that amalgamates two gain sections with different bandgap energies. This is achieved using selective area intermixing of the multiple quantum wells, and impurity-free vacancy induced disordering. When different current combination is injected into each section, that leads to a laser wavelength peak whose position depends on the relative magnitudes of the two injected currents. The laser wavelength can be fine...
Show moreIn this work, we demonstrate an InGaAsP multiple quantum well tunable laser diode that amalgamates two gain sections with different bandgap energies. This is achieved using selective area intermixing of the multiple quantum wells, and impurity-free vacancy induced disordering. When different current combination is injected into each section, that leads to a laser wavelength peak whose position depends on the relative magnitudes of the two injected currents. The laser wavelength can be fine-tuned from 1538 nm to 1578 nm with relatively constant output power. The free spectral range FSR of the tunable laser found to be 0.25 nm. This tunable laser was launched into an optical surface plasmon resonance sensor head to provide an input light source for the SPR sensor.Using the tunable laser diode, we have demonstrated an optical surface plasmon resonance sensor head that is based on an inverted rib dielectric waveguide, in which the resonance wavelength of the surface plasmon excited at the gold metal-dielectric interface depends on the refractive index of the liquid in contact with it. The inverted-rib waveguide of the SPR sensor head is made of a layer of SU-8 polymer with a refractive index of 1.568. While the lower cladding layer consists of silicon oxynitride (SiOxNy) with a refractive index of 1.526. The top surface is coated with 20 nm of chromium followed by a 50 nm thick layer of gold or with 4 nm of titanium followed by a 25 nm thick layer of gold. The SPR sensor head was designed, to allow monitoring of analyte media with a refractive index, ranging from 1.43 to the 1.52. Using a set of reference liquids representing the analyte medium, the sensitivity of the SPR sensor was measured using the fabricated tunable laser, an optical spectrum analyzer, and a photodiode. It was found that with various calibrated sample liquids in contact with the gold metal, a sharp resonance dip in the transmission spectrum occurred, and its position shifted to a shorter wavelength when the refractive index of the sample liquids was increased. The average sensitivity of the SPR sensor devices was determined to be S = 334 nm/RIU.
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Date Issued: 2018
Identifier: CFE0007769, ucf:52390
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007769

Title: Hurricane Imaging Radiometer (HIRAD) tropical rainfall retrievals.
Creator: Alasgah, Abdusalam, Jones, W Linwood, Wahid, Parveen, Mikhael, Wasfy, Gong, Xun, Zec, Josko, University of Central Florida
Abstract / Description: The Hurricane Imaging Radiometer (HIRAD) is an airborne passive microwave remote sensor, developed to measure wind speed and rain rate in hurricanes. This dissertation concerns the development of a signal processing algorithm to infer tropical rainfall from HIRAD radiance (brightness temperature, Tb) measurements.The basis of the rain rate retrieval algorithm is an improved forward microwave radiative transfer model (RTM) that incorporates the HIRAD multi-antenna-beam geometry, and uses semi...
Show moreThe Hurricane Imaging Radiometer (HIRAD) is an airborne passive microwave remote sensor, developed to measure wind speed and rain rate in hurricanes. This dissertation concerns the development of a signal processing algorithm to infer tropical rainfall from HIRAD radiance (brightness temperature, Tb) measurements.The basis of the rain rate retrieval algorithm is an improved forward microwave radiative transfer model (RTM) that incorporates the HIRAD multi-antenna-beam geometry, and uses semi-empirical coefficients derived from an airborne experiment that occurred in the Gulf of Mexico off Tampa Bay in 2013. During this flight, HIRAD observed a squall line of thunderstorms simultaneously with an airborne meteorological radar (High Altitude Wind and Rain Profiler, HIWRAP), located on the same airplane. Also, ground based NEXRAD radars from the National Weather Service (located at Tampa and Tallahassee) provided high resolution simultaneous rain rate measurements.Using NEXRAD rainfall as the surface truth input to the HIRAD RTM, empirical rain microwave absorption coefficients were tuned to match the measured brightness temperatures. Also, the collocated HIWRAP radar reflectivity (dBZ) measurements were cross correlated with NEXRAD to derive the empirical HIWRAP radar reflectivity to rain rate relationship. Finally, the HIRAD measured Tbs were input to the HIRAD rain retrieval algorithm to derive estimates of rain rate, which were validated using the independent HIWRAP measurements of rain rate.
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Date Issued: 2019
Identifier: CFE0007775, ucf:52379
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007775

Title: Advanced Control Techniques for Efficiency and Power Density Improvement of a Three-Phase Microinverter.
Creator: Tayebi, Seyed Milad, Batarseh, Issa, Mikhael, Wasfy, Sundaram, Kalpathy, Sun, Wei, Kutkut, Nasser, University of Central Florida
Abstract / Description: Inverters are widely used in photovoltaic (PV) based power generation systems. Most of these systems have been based on medium to high power string inverters. Microinverters are gaining popularity over their string inverter counterparts in PV based power generation systems due to maximized energy harvesting, high system reliability, modularity, and simple installation. They can be deployed on commercial buildings, residential rooftops, electric poles, etc and have a huge potential market....
Show moreInverters are widely used in photovoltaic (PV) based power generation systems. Most of these systems have been based on medium to high power string inverters. Microinverters are gaining popularity over their string inverter counterparts in PV based power generation systems due to maximized energy harvesting, high system reliability, modularity, and simple installation. They can be deployed on commercial buildings, residential rooftops, electric poles, etc and have a huge potential market. Emerging trend in power electronics is to increase power density and efficiency while reducing cost. A powerful tool to achieve these objectives is the development of an advanced control system for power electronics. In low power applications such as solar microinverters, increasing the switching frequency can reduce the size of passive components resulting in higher power density. However, switching losses and electromagnetic interference (EMI) may increase as a consequence of higher switching frequency. Soft switching techniques have been proposed to overcome these issues. This dissertation presents several innovative control techniques which are used to increase efficiency and power density while reducing cost. Dynamic dead time optimization and dual zone modulation techniques have been proposed in this dissertation to significantly improve the microinverter efficiency. In dynamic dead time optimization technique, pulse width modulation (PWM) dead times are dynamically adjusted as a function of load current to minimize MOSFET body diode conduction time which reduces power dissipation. This control method also improves total harmonic distortion (THD) of the inverter output current. To further improve the microinverter efficiency, a dual-zone modulation has been proposed which introduces one more soft-switching transition and lower inductor peak current compared to the other boundary conduction mode (BCM) modulation methods.In addition, an advanced DC link voltage control has been proposed to increase the microinverter power density. This concept minimizes the storage capacitance by allowing greater voltage ripple on the DC link. Therefore, the microinverter reliability can be significantly increased by replacing electrolytic capacitors with film capacitors. These control techniques can be readily implemented on any inverter, motor controller, or switching power amplifier. Since there is no circuit modification involved in implementation of these control techniques and can be easily added to existing controller firmware, it will be very attractive to any potential licensees.
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Date Issued: 2017
Identifier: CFE0007136, ucf:52328
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007136

Title: Sparse signal recovery under sensing and physical hardware constraints.
Creator: Mardaninajafabadi, Davood, Atia, George, Mikhael, Wasfy, Vosoughi, Azadeh, Rahnavard, Nazanin, Abouraddy, Ayman, University of Central Florida
Abstract / Description: This dissertation focuses on information recovery under two general types of sensing constraints and hardware limitations that arise in practical data acquisition systems. We study the effects of these practical limitations in the context of signal recovery problems from interferometric measurements such as for optical mode analysis.The first constraint stems from the limited number of degrees of freedom of an information gathering system, which gives rise to highly constrained sensing...
Show moreThis dissertation focuses on information recovery under two general types of sensing constraints and hardware limitations that arise in practical data acquisition systems. We study the effects of these practical limitations in the context of signal recovery problems from interferometric measurements such as for optical mode analysis.The first constraint stems from the limited number of degrees of freedom of an information gathering system, which gives rise to highly constrained sensing structures. In contrast to prior work on compressive signal recovery which relies for the most part on introducing additional hardware components to emulate randomization, we establish performance guarantees for successful signal recovery from a reduced number of measurements even with the constrained interferometer structure obviating the need for non-native components. Also, we propose control policies to guide the collection of informative measurements given prior knowledge about the constrained sensing structure. In addition, we devise a sequential implementation with a stopping rule, shown to reduce the sample complexity for a target performance in reconstruction.The second limitation considered is due to physical hardware constraints, such as the finite spatial resolution of the used components and their finite aperture size. Such limitations introduce non-linearities in the underlying measurement model. We first develop a more accurate measurement model with structured noise representing a known non-linear function of the input signal, obtained by leveraging side information about the sampling structure. Then, we devise iterative denoising algorithms shown to enhance the quality of sparse recovery in the presence of physical constraints by iteratively estimating and eliminating the non-linear term from the measurements. We also develop a class of clipping-cognizant reconstruction algorithms for modal reconstruction from interferometric measurements that compensate for clipping effects due to the finite aperture size of the used components and show they yield significant gains over schemes oblivious to such effects.
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Date Issued: 2019
Identifier: CFE0007675, ucf:52467
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007675

Title: Different Facial Recognition Techniques in Transform Domains.
Creator: Al Obaidi, Taif, Mikhael, Wasfy, Atia, George, Jones, W Linwood, Myers, Brent, Moslehy, Faissal, University of Central Florida
Abstract / Description: The human face is frequently used as the biometric signal presented to a machine for identificationpurposes. Several challenges are encountered while designing face identification systems.The challenges are either caused by the process of capturing the face image itself, or occur whileprocessing the face poses. Since the face image not only contains the face, this adds to the datadimensionality, and thus degrades the performance of the recognition system. Face Recognition(FR) has been a major...
Show moreThe human face is frequently used as the biometric signal presented to a machine for identificationpurposes. Several challenges are encountered while designing face identification systems.The challenges are either caused by the process of capturing the face image itself, or occur whileprocessing the face poses. Since the face image not only contains the face, this adds to the datadimensionality, and thus degrades the performance of the recognition system. Face Recognition(FR) has been a major signal processing topic of interest in the last few decades. Most commonapplications of the FR include, forensics, access authorization to facilities, or simply unlockingof a smart phone. The three factors governing the performance of a FR system are: the storagerequirements, the computational complexity, and the recognition accuracy. The typical FR systemconsists of the following main modules in each of the Training and Testing phases: Preprocessing,Feature Extraction, and Classification. The ORL, YALE, FERET, FEI, Cropped AR, and GeorgiaTech datasets are used to evaluate the performance of the proposed systems. The proposed systemsare categorized into Single-Transform and Two-Transform systems. In the first category, the featuresare extracted from a single domain, that of the Two-Dimensional Discrete Cosine Transform(2D DCT). In the latter category, the Two-Dimensional Discrete Wavelet Transform (2D DWT)coefficients are combined with those of the 2D DCT to form one feature vector. The feature vectorsare either used directly or further processed to obtain the persons' final models. The PrincipleComponent Analysis (PCA), the Sparse Representation, Vector Quantization (VQ) are employedas a second step in the Feature Extraction Module. Additionally, a technique is proposed in whichthe feature vector is composed of appropriately selected 2D DCT and 2D DWT coefficients basedon a residual minimization algorithm.
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Date Issued: 2018
Identifier: CFE0007146, ucf:52295
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007146

Title: Analysis, Design and Efficiency Optimization of Power Converters for Renewable Energy Applications.
Creator: Chen, Xi, Batarseh, Issa, Zhou, Qun, Mikhael, Wasfy, Sun, Wei, Kutkut, Nasser, University of Central Florida
Abstract / Description: DC-DC power converters are widely used in renewable energy-based power generation systems due to the constant demand of high-power density and high-power conversion efficiency. DC-DC converters can be classified into non-isolated and isolated topologies. For non-isolated topologies, they are typically derived from buck, boost, buck-boost or forth order (such as Cuk, Sepic and Zeta) converters and they usually have relatively higher conversion efficiency than isolated topologies. However, with...
Show moreDC-DC power converters are widely used in renewable energy-based power generation systems due to the constant demand of high-power density and high-power conversion efficiency. DC-DC converters can be classified into non-isolated and isolated topologies. For non-isolated topologies, they are typically derived from buck, boost, buck-boost or forth order (such as Cuk, Sepic and Zeta) converters and they usually have relatively higher conversion efficiency than isolated topologies. However, with the applications where the isolation is required, either these topologies should be modified, or alternative topologies are needed. Among various isolated DC-DC converters, the LLC resonant converter is an attractive selection due to its soft switching, isolation, wide gain range, high reliability, high power density and high conversion efficiency.In low power applications, such as battery chargers and solar microinverters, increasing the switching frequency can reduce the size of passive components and reduce the current ripple and root-mean-square (RMS) current, resulting in higher power density and lower conduction loss. However, switching losses, gate driving loss and electromagnetic interference (EMI) may increase as a consequence of higher switching frequency. Therefore, switching frequency modulation, components optimization and soft switching techniques have been proposed to overcome these issues and achieve a tradeoff to reach the maximum conversion efficiency.This dissertation can be divided into two categories: the first part is focusing on the well-known non-isolated bidirectional cascaded-buck-boost converter, and the second part is concentrating on the isolated dual-input single resonant tank LLC converter. Several optimization approaches have been presented to improve the efficiency, power density and reliability of the power converters. In the first part, an adaptive switching frequency modulation technique has been proposed based on the precise loss model in this dissertation to increase the efficiency of the cascaded-buck-boost converter. In adaptive switching frequency modulation technique, the optimal switching frequency for the cascaded-buck-boost converter is adaptively selected to achieve the minimum total power loss. In addition, due to the major power losses coming from the inductor, a new low profile nanocrystalline inductor filled with copper foil has been designed to significantly reduce the core loss and winding loss. To further improve the efficiency of the cascaded-buck-boost converter, the adaptive switching frequency modulation technique has been applied on the converter with designed nanocrystalline inductor, in which the peak efficiency of the converter can break the 99% bottleneck.In the second part, a novel dual-input DC-DC converter is developed according to the LLC resonant topology. This design concept minimizes the circuit components by allowing single resonant tank to interface with multiple input sources. Based on different applications, the circuit configuration for the dual-input LLC converter will be a little different. In order to improve the efficiency of the dual-input LLC converter, the semi-active rectifiers have been used on the transformer secondary side to replace the low-side bridge diodes. In this case, higher magnetizing inductance can be selected while maintaining the same voltage gain. Besides, a burst-mode control strategy has been proposed to improve the light load and very light load efficiency of the dual- input LLC converter. This control strategy is able to be readily implemented on any power converter since it can be achieved directly through firmware and no circuit modification is needed in implementation of this strategy.
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Date Issued: 2019
Identifier: CFE0007612, ucf:52531
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007612

Title: Complex-valued adaptive digital signal enhancement for applications in wireless communication systems.
Creator: Liu, Ying, Mikhael, Wasfy, Batarseh, Issa, Yang, Thomas, Hunter, Matthew, Haralambous, Michael, Myers, Brent, University of Central Florida
Abstract / Description: In recent decades, the wireless communication industry has attracted a great deal of research efforts to satisfy rigorous performance requirements and preserve high spectral efficiency. Along with this trend, I/Q modulation is frequently applied in modern wireless communications to develop high performance and high data rate systems. This has necessitated the need for applying efficient complex-valued signal processing techniques to highly-integrated, multi-standard receiver devices.In this...
Show moreIn recent decades, the wireless communication industry has attracted a great deal of research efforts to satisfy rigorous performance requirements and preserve high spectral efficiency. Along with this trend, I/Q modulation is frequently applied in modern wireless communications to develop high performance and high data rate systems. This has necessitated the need for applying efficient complex-valued signal processing techniques to highly-integrated, multi-standard receiver devices.In this dissertation, novel techniques for complex-valued digital signal enhancement are presented and analyzed for various applications in wireless communications. The first technique is a unified block processing approach to generate the complex-valued conjugate gradient Least Mean Square (LMS) techniques with optimal adaptations. The proposed algorithms exploit the concept of the complex conjugate gradients to find the orthogonal directions for updating the adaptive filter coefficients at each iteration. Along each orthogonal direction, the presented algorithms employ the complex Taylor series expansion to calculate time-varying convergence factors tailored for the adaptive filter coefficients. The performance of the developed technique is tested in the applications of channel estimation, channel equalization, and adaptive array beamforming. Comparing with the state of the art methods, the proposed techniques demonstrate improved performance and exhibit desirable characteristics for practical use.The second complex-valued signal processing technique is a novel Optimal Block Adaptive algorithm based on Circularity, OBA-C. The proposed OBA-C method compensates for a complex imbalanced signal by restoring its circularity. In addition, by utilizing the complex Taylor series expansion, the OBA-C method optimally updates the adaptive filter coefficients at each iteration. This algorithm can be applied to mitigate the frequency-dependent I/Q mismatch effects in analog front-end. Simulation results indicate that comparing with the existing methods, OBA-C exhibits superior convergence speed while maintaining excellent accuracy. The third technique is regarding interference rejection in communication systems. The research on both LMS and Independent Component Analysis (ICA) based techniques continues to receive significant attention in the area of interference cancellation. The performance of the LMS and ICA based approaches is studied for signals with different probabilistic distributions. Our research indicates that the ICA-based approach works better for super-Gaussian signals, while the LMS-based method is preferable for sub-Gaussian signals. Therefore, an appropriate choice of interference suppression algorithms can be made to satisfy the ever-increasing demand for better performance in modern receiver design.
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Date Issued: 2012
Identifier: CFE0004572, ucf:49192
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004572

Title: Analysis and Design Optimization of Resonant DC-DC Converters.
Creator: Fang, Xiang, Shen, Zheng, Batarseh, Issa, Mikhael, Wasfy, Wu, Xinzhang, Kutkut, Nasser, University of Central Florida
Abstract / Description: The development in power conversion technology is in constant demand of high power efficiency and high power density. The DC-DC power conversion is an indispensable stage for numerous power supplies and energy related applications. Particularly, in PV micro-inverters and front-end converter of power supplies, great challenges are imposed on the power performances of the DC-DC converter stage, which not only require high efficiency and density but also the capability to regulate a wide...
Show moreThe development in power conversion technology is in constant demand of high power efficiency and high power density. The DC-DC power conversion is an indispensable stage for numerous power supplies and energy related applications. Particularly, in PV micro-inverters and front-end converter of power supplies, great challenges are imposed on the power performances of the DC-DC converter stage, which not only require high efficiency and density but also the capability to regulate a wide variation range of input voltage and load conditions. The resonant DC-DC converters are good candidates to meet these challenges with the advantages of achieving soft switching and low EMI. Among the resonant converters, the LLC converter is very attractive for its high gain range and providing ZVS from full load to zero load condition. The operation of the LLC converter is complicated due to its multiple resonant stage mechanism. In this dissertation, a literature review of different analysis methods are presented, and it shows that the study on the LLC is still incomplete. Therefore, an operation mode analysis method is proposed, which divides the operation into six major modes based on the occurrence of resonant stages. The resonant currents, voltages and the DC gain characteristics for each mode is investigated. To get a thorough view of the converter behavior, the boundaries of every mode are studied, and the mode distribution is discussed. An experimental prototype is built and tested to demonstrate its accuracy in operation waveforms and gain prediction. Since most of the LLC modes have no closed-form solutions, simplification is necessary in order to utilize this mode model in practical design. As the peak gain is an important design parameters indicating the LLC's operating limit of input voltage and switching frequency, a numerical peak gain approximation method is developed, which provide a direct way to calculate the peak gain and its corresponding load and frequency condition. In addition, as PO mode is the most favorable operation mode of the LLC, its operation region is investigated and an approximation approach is developed to determine its boundary. The design optimization of the LLC has always been a difficult problem as there are many parameters affecting the design and it lacks clear design guidance in selecting the optimal resonant tank parameters. Based on the operation mode model, three optimization methods are proposed according to the design scenarios. These methods focus on minimize the conduction loss of resonant tank while maintaining the required voltage gain level, and the approximations of peak gains and mode boundary can be applied here to facilitate the design. A design example is presented following one of the optimization procedure. As a comparison, the L-C component values are reselected and tested while the design specifications are the same. The experiments show that the optimal design has better efficiency performance. Finally, a generalized approach for resonant converter analysis is developed. It can be implemented by computer programs or numerical analysis tools to derive the operation waveforms and DC characteristics of resonant converters.
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Date Issued: 2012
Identifier: CFE0004229, ucf:49026
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004229

Title: Evaluation of the Hurricane Imaging Radiometer (HIRAD) Brightness Temperatures.
Creator: Sahawneh, Saleem, Jones, W Linwood, Mikhael, Wasfy, Wahid, Parveen, Zec, Josko, University of Central Florida
Abstract / Description: The Hurricane Imaging Radiometer (HIRAD) is an experimental, airborne, microwave remote sensor that was developed to measure hurricane surface wind speed and rain rate, and thereby, provide data for scientific research and for the next generation operational hurricane surveillance. The object of this dissertation is to develop objective procedures and techniques that can be used to evaluate and characterize the HIRAD brightness temperature (Tb) image product provided by NASA MSFC.First, the...
Show moreThe Hurricane Imaging Radiometer (HIRAD) is an experimental, airborne, microwave remote sensor that was developed to measure hurricane surface wind speed and rain rate, and thereby, provide data for scientific research and for the next generation operational hurricane surveillance. The object of this dissertation is to develop objective procedures and techniques that can be used to evaluate and characterize the HIRAD brightness temperature (Tb) image product provided by NASA MSFC.First, the approach that was developed for geolocation (latitude and longitude) accuracy determination of HIRAD image pixels is presented. Using statistical estimation theory, high-contrast HIRAD imagery are compared with high resolution maps at land/water boundaries, and an error model and measurement results are presented for a variety of pixel locations. Also, a procedure is presented for estimating the HIRAD feature resolution, i.e., the effective spatial resolution (instantaneous field of view, IFOV) in the HIRAD Tb images. Next, the objective technique developed to evaluate HIRAD reconstructed ocean brightness temperature (Tb) images is described and presented. Examples are presented for several ocean scenes, which covers a wide range of ocean wind speed conditions that include Hurricanes. For these cases, surface truth in the form of independent ocean brightness temperatures measurements are obtained by airborne microwave radiometers for comparison.
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Date Issued: 2017
Identifier: CFE0006653, ucf:51221
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006653

Title: investigation of dual-stage high efficiency (&)density micro inverter for solar application.
Creator: Chen, Lin, Batarseh, Issa, Mikhael, Wasfy, Wu, Xinzhang, Behal, Aman, Kutkut, Nasser, University of Central Florida
Abstract / Description: Module integrated converters (MIC), also called micro inverter, in single phase have witnessed recent market success due to unique features (1) improved energy harvest, (2) improved system efficiency, (3) lower installation costs, (4) plug-N-play operation, (5) and enhanced flexibility and modularity. The MIC sector has grown from a niche market to mainstream, especially in the United States. Due to the fact that two-stage architecture is commonly used for single phase MIC application. A DC...
Show moreModule integrated converters (MIC), also called micro inverter, in single phase have witnessed recent market success due to unique features (1) improved energy harvest, (2) improved system efficiency, (3) lower installation costs, (4) plug-N-play operation, (5) and enhanced flexibility and modularity. The MIC sector has grown from a niche market to mainstream, especially in the United States. Due to the fact that two-stage architecture is commonly used for single phase MIC application. A DC-DC stage with maximum power point tracking to boost the output voltage of the Photovoltaic (PV) panel is employed in the first stage, DC-AC stage is used for use to connect the grid or the residential application. As well known, the cost of MIC is key issue compared to convention PV system, such as the architecture: string inverter or central inverter. A high efficiency and density DC-DC converter is proposed and dedicated for MIC application. Assuming further expansion of the MIC market, this dissertation presents the micro-inverter concept incorporated in large size PV installations such as MW-class solar farms where a three phase AC connection is employed. A high efficiency three phase MIC with two-stage ZVS operation for grid tied photovoltaic system is proposed which will reduce cost per watt, improve reliability, and increase scalability of MW-class solar farms through the development of new solar farm system architectures. This dissertation presents modeling and triple-loop control for a high efficiency three-phase four-wire inverter for use in grid-connected two-stage micro inverter applications. An average signal model based on a synchronous rotation frame for a three-phase four-wire inverter has been developed. The inner current loop consists of a variable frequency bidirectional current mode (VFBCM) controller which regulates output filter inductor current thereby achieving ZVS, improved system response, and reduced grid current THD. Active damping of the LCL output filter using filter inductor current feedback is discussed along with small signal modeling of the proposed control method. Since the DC-link capacitor plays a critical role in two-stage micro inverter applications, a DC-link controller is implemented outside of the two current control loops to keep the bus voltage constant. In the end, simulation and experimental results from a 400 watt prototype are presented to verify the validity of the theoretical analysis.
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Date Issued: 2014
Identifier: CFE0005148, ucf:50699
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005148

Title: Control Based Soft Switching Three-phase Micro-inverter: Efficiency and Power Density Optimization.
Creator: Amirahmadi, Ahmadreza, Batarseh, Issa, Lotfifard, Saeed, Mikhael, Wasfy, Wu, Xinzhang, Kutkut, Nasser, University of Central Florida
Abstract / Description: In the field of renewable energy, solar photovoltaic is growing exponentially. Grid-tied PV micro-inverters have become the trend for future PV system development because of their remarkable advantages such as enhanced energy production due to MPPT implementation for each PV panel, high reliability due to redundant and distributed system architecture, and simple design, installation, and management due to its plug-and-play feature. Conventional approaches for the PV micro-inverters are mainly...
Show moreIn the field of renewable energy, solar photovoltaic is growing exponentially. Grid-tied PV micro-inverters have become the trend for future PV system development because of their remarkable advantages such as enhanced energy production due to MPPT implementation for each PV panel, high reliability due to redundant and distributed system architecture, and simple design, installation, and management due to its plug-and-play feature. Conventional approaches for the PV micro-inverters are mainly in the form of single-phase grid connected and they aim at the residential and commercial rooftop applications. It would be advantageous to extend the micro-inverter concept to large size PV installations such as MW-class solar farms where three-phase AC connections are used.The relatively high cost of the three-phase micro-inverter is the biggest barrier to its large scale deployment. Increasing the switching frequency may be the best way to reduce cost by shrinking the size of reactive components and heat-sink. However, this approach could cause conversion efficiency to drop dramatically without employing soft switching techniques or using costly new devices.This dissertation presents a new zero voltage switching control method that is suitable for low power applications such as three-phase micro-inverters. The proposed hybrid boundary conduction mode (BCM) current control method increases the efficiency and power density of the micro-inverters and features both reduced number of components and easy digital implementation. Zero voltage switching is achieved by controlling the inductor current bi-directional in every switching cycle and results in lower switching losses, higher operating frequency, and reduced size and cost of passive components, especially magnetic cores. Some practical aspects of hybrid control implementation such as dead-time insertion can degrade the performance of the micro-inverter. A dead-time compensation method that improves the performance of hybrid BCM current control by decreasing the output current THD and reducing the zero crossing distortion is presented.Different BCM ZVS current control modulation schemes are compared based on power losses breakdown, switching frequency range, and current quality. Compared to continuous conduction mode (CCM) current control, BCM ZVS control decreases MOSFET switching losses and filter inductor conduction losses but increases MOSFET conduction losses and inductor core losses. Based on the loss analysis, a dual-mode current modulation method combining ZVS and zero current switching (ZCS) schemes is proposed to improve the efficiency of the micro-inverter.Finally, a method of maintaining high power conversion efficiency across the entire load range of the three-phase micro-inverter is proposed. The proposed control method substantially increases the conversion efficiency at light loads by minimizing switching losses of semiconductor devices as well as core losses of magnetic components. This is accomplished by entering a phase skipping operating mode wherein two phases of an inverter are disabled and three inverters are combined to form a new three-phase system with minimal grid imbalance. A 400W prototype of a three-phase micro-inverter and its hybrid control system have been designed and tested under different conditions to verify the effectiveness of the proposed controller, current modulation scheme, and light load efficiency enhancement method.
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Date Issued: 2014
Identifier: CFE0005125, ucf:50703
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005125

Title: Probabilistic-Based Computing Transformation with Reconfigurable Logic Fabrics.
Creator: Alawad, Mohammed, Lin, Mingjie, DeMara, Ronald, Mikhael, Wasfy, Wang, Jun, Das, Tuhin, University of Central Florida
Abstract / Description: Effectively tackling the upcoming (")zettabytes(") data explosion requires a huge quantum leapin our computing power and energy efficiency. However, with the Moore's law dwindlingquickly, the physical limits of CMOS technology make it almost intractable to achieve highenergy efficiency if the traditional (")deterministic and precise(") computing model still dominates.Worse, the upcoming data explosion mostly comprises statistics gleaned from uncertain,imperfect real-world environment. As such...
Show moreEffectively tackling the upcoming (")zettabytes(") data explosion requires a huge quantum leapin our computing power and energy efficiency. However, with the Moore's law dwindlingquickly, the physical limits of CMOS technology make it almost intractable to achieve highenergy efficiency if the traditional (")deterministic and precise(") computing model still dominates.Worse, the upcoming data explosion mostly comprises statistics gleaned from uncertain,imperfect real-world environment. As such, the traditional computing means of first-principlemodeling or explicit statistical modeling will very likely be ineffective to achieveflexibility, autonomy, and human interaction. The bottom line is clear: given where we areheaded, the fundamental principle of modern computing(-)deterministic logic circuits canflawlessly emulate propositional logic deduction governed by Boolean algebra(-)has to bereexamined, and transformative changes in the foundation of modern computing must bemade.This dissertation presents a novel stochastic-based computing methodology. It efficientlyrealizes the algorithmatic computing through the proposed concept of Probabilistic DomainTransform (PDT). The essence of PDT approach is to encode the input signal asthe probability density function, perform stochastic computing operations on the signal inthe probabilistic domain, and decode the output signal by estimating the probability densityfunction of the resulting random samples. The proposed methodology possesses manynotable advantages. Specifically, it uses much simplified circuit units to conduct complexoperations, which leads to highly area- and energy-efficient designs suitable for parallel processing.Moreover, it is highly fault-tolerant because the information to be processed isencoded with a large ensemble of random samples. As such, the local perturbations of itscomputing accuracy will be dissipated globally, thus becoming inconsequential to the final overall results. Finally, the proposed probabilistic-based computing can facilitate buildingscalable precision systems, which provides an elegant way to trade-off between computingaccuracy and computing performance/hardware efficiency for many real-world applications.To validate the effectiveness of the proposed PDT methodology, two important signal processingapplications, discrete convolution and 2-D FIR filtering, are first implemented andbenchmarked against other deterministic-based circuit implementations. Furthermore, alarge-scale Convolutional Neural Network (CNN), a fundamental algorithmic building blockin many computer vision and artificial intelligence applications that follow the deep learningprinciple, is also implemented with FPGA based on a novel stochastic-based and scalablehardware architecture and circuit design. The key idea is to implement all key componentsof a deep learning CNN, including multi-dimensional convolution, activation, and poolinglayers, completely in the probabilistic computing domain. The proposed architecture notonly achieves the advantages of stochastic-based computation, but can also solve severalchallenges in conventional CNN, such as complexity, parallelism, and memory storage.Overall, being highly scalable and energy efficient, the proposed PDT-based architecture iswell-suited for a modular vision engine with the goal of performing real-time detection, recognitionand segmentation of mega-pixel images, especially those perception-based computingtasks that are inherently fault-tolerant.
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Date Issued: 2016
Identifier: CFE0006828, ucf:51768
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006828

Title: On-orbit Inter-satellite Radiometric Calibration of Cross-track Scanning Microwave Radiometers.
Creator: Ebrahimi, Hamideh, Jones, W Linwood, Mikhael, Wasfy, Wahid, Parveen, Wang, James, Wilheit, Thomas, University of Central Florida
Abstract / Description: This dissertation concerns the development of an improved algorithm for the inter-satellite radiometric calibration (XCAL) for cross track scanning microwave radiometers in support of NASA's Global Precipitation Mission (GPM). This research extends previous XCAL work to assess the robustness of the CFRSL (")double difference(") technique for sounder X-CAL. In this work, using a two-year of observations, we present a statistical analysis of radiometric biases performed over time and viewing...
Show moreThis dissertation concerns the development of an improved algorithm for the inter-satellite radiometric calibration (XCAL) for cross track scanning microwave radiometers in support of NASA's Global Precipitation Mission (GPM). This research extends previous XCAL work to assess the robustness of the CFRSL (")double difference(") technique for sounder X-CAL. In this work, using a two-year of observations, we present a statistical analysis of radiometric biases performed over time and viewing geometry. In theory, it is possible to apply the same X-CAL procedure developed for conical-scanning radiometers to cross-track scanners; however the implementation is generally more tedious. For example, with the cross-track scan angle, there is a strong response in the observed Tb due to changes in the atmosphere slant path and surface emissivity with the Earth incidence angle. For ocean scenes this is trivial; however for land scenes there is imperfect knowledge of polarized emissivity. However, for the sounder channels the surface emissivity is not the dominant component of top-of-the-atmosphere Tb, which is a mitigating factor. Also, cross-track scanners introduce changes in the radiometer antenna observed polarization with scan angle. The resulting observation is a mixture of un-polarized atmospheric emissions and vertical and horizontal polarized surface emissions. The degree of polarization mixing is known from geometry; however, reasonable estimates of the surface emissivity are required, which complicate over land comparisons. Finally, the IFOV size monotonically increases over the cross-track scan. Thus, when inter-comparing cross-track scanning radiometers, it will be necessary to carefully consider these effects when performing the double difference procedure.
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Date Issued: 2016
Identifier: CFE0006453, ucf:51411
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006453

Title: Creating a Consistent Oceanic Multi-decadal Intercalibrated TMI-GMI Constellation Data Record.
Creator: Chen, Ruiyao, Jones, W Linwood, Mikhael, Wasfy, Wei, Lei, Wilheit, Thomas, McKague, Darren, University of Central Florida
Abstract / Description: The Tropical Rainfall Measuring Mission (TRMM), launched in late November 1997 into a low earth orbit, produced the longest microwave radiometric data time series of 17-plus years from the TRMM Microwave Imager (TMI). The Global Precipitation Measuring (GPM) mission is the follow-on to TRMM, designed to provide data continuity and advance precipitation measurement capabilities. The GPM Microwave Imager (GMI) performs as a brightness temperature (Tb) calibration standard for the intersatellite...
Show moreThe Tropical Rainfall Measuring Mission (TRMM), launched in late November 1997 into a low earth orbit, produced the longest microwave radiometric data time series of 17-plus years from the TRMM Microwave Imager (TMI). The Global Precipitation Measuring (GPM) mission is the follow-on to TRMM, designed to provide data continuity and advance precipitation measurement capabilities. The GPM Microwave Imager (GMI) performs as a brightness temperature (Tb) calibration standard for the intersatellite radiometric calibration (XCAL) for the other constellation members; and before GPM was launched, TMI was the XCAL standard. This dissertation aims at creating a consistent oceanic multi-decadal Tb data record that ensures an undeviating long-term precipitation record covering TRMM-GPM eras. As TMI and GMI share only a 13-month common operational period, the U.S. Naval Research Laboratory's WindSat radiometer, launched in 2003 and continuing today provides the calibration bridge between the two. TMI/WindSat XCAL for their (>)9 years' period, and WindSat/GMI XCAL for one year are performed using a robust technique developed by the Central Florida Remote Sensing Lab, named CFRSL XCAL Algorithm, to estimate the Tb bias of one relative to the other. The 3-way XCAL of GMI/TMI/WindSat for their joint overlap period is performed using an extended CFRSL XCAL algorithm. Thus, a multi-decadal oceanic Tb dataset is created. Moreover, an important feature of this dataset is a quantitative estimate of the Tb uncertainty derived from a generic Uncertainty Quantification Model (UQM). In the UQM, various sources contributing to the Tb bias are identified systematically. Next, methods for quantifying uncertainties from these sources are developed and applied individually. Finally, the resulting independent uncertainties are combined into a single overall uncertainty to be associated with the Tb bias on a channel basis. This dissertation work is remarkably important because it provides the science community with a consistent oceanic multi-decadal Tb data record, and also allows the science community to better understand the uncertainty in precipitation products based upon the Tb uncertainties provided.
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Date Issued: 2018
Identifier: CFE0006987, ucf:51650
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006987

Title: High Performance Techniques for Face Recognition.
Creator: Aldhahab, Ahmed, Mikhael, Wasfy, Atia, George, Jones, W Linwood, Wei, Lei, Elshennawy, Ahmad, University of Central Florida
Abstract / Description: The identification of individuals using face recognition techniques is a challenging task. This is due to the variations resulting from facial expressions, makeup, rotations, illuminations, gestures, etc. Also, facial images contain a great deal of redundant information, which negatively affects the performance of the recognition system. The dimensionality and the redundancy of the facial features have a direct effect on the face recognition accuracy. Not all the features in the feature...
Show moreThe identification of individuals using face recognition techniques is a challenging task. This is due to the variations resulting from facial expressions, makeup, rotations, illuminations, gestures, etc. Also, facial images contain a great deal of redundant information, which negatively affects the performance of the recognition system. The dimensionality and the redundancy of the facial features have a direct effect on the face recognition accuracy. Not all the features in the feature vector space are useful. For example, non-discriminating features in the feature vector space not only degrade the recognition accuracy but also increase the computational complexity.In the field of computer vision, pattern recognition, and image processing, face recognition has become a popular research topic. This is due to its wide spread applications in security and control, which allow the identified individual to access secure areas, personal information, etc. The performance of any recognition system depends on three factors: 1) the storage requirements, 2) the computational complexity, and 3) the recognition rates.Two different recognition system families are presented and developed in this dissertation. Each family consists of several face recognition systems. Each system contains three main steps, namely, preprocessing, feature extraction, and classification. Several preprocessing steps, such as cropping, facial detection, dividing the facial image into sub-images, etc. are applied to the facial images. This reduces the effect of the irrelevant information (background) and improves the system performance. In this dissertation, either a Neural Network (NN) based classifier or Euclidean distance is used for classification purposes. Five widely used databases, namely, ORL, YALE, FERET, FEI, and LFW, each containing different facial variations, such as light condition, rotations, facial expressions, facial details, etc., are used to evaluate the proposed systems. The experimental results of the proposed systems are analyzed using K-folds Cross Validation (CV).In the family-1, Several systems are proposed for face recognition. Each system employs different integrated tools in the feature extraction step. These tools, Two Dimensional Discrete Multiwavelet Transform (2D DMWT), 2D Radon Transform (2D RT), 2D or 3D DWT, and Fast Independent Component Analysis (FastICA), are applied to the processed facial images to reduce the dimensionality and to obtain discriminating features. Each proposed system produces a unique representation, and achieves less storage requirements and better performance than the existing methods.For further facial compression, there are three face recognition systems in the second family. Each system uses different integrated tools to obtain better facial representation. The integrated tools, Vector Quantization (VQ), Discrete cosine Transform (DCT), and 2D DWT, are applied to the facial images for further facial compression and better facial representation. In the systems using the tools VQ/2D DCT and VQ/ 2D DWT, each pose in the databases is represented by one centroid with 4*4*16 dimensions. In the third system, VQ/ Facial Part Detection (FPD), each person in the databases is represented by four centroids with 4*Centroids (4*4*16) dimensions. The systems in the family-2 are proposed to further reduce the dimensions of the data compared to the systems in the family-1 while attaining comparable results. For example, in family-1, the integrated tools, FastICA/ 2D DMWT, applied to different combinations of sub-images in the FERET database with K-fold=5 (9 different poses used in the training mode), reduce the dimensions of the database by 97.22% and achieve 99% accuracy. In contrast, the integrated tools, VQ/ FPD, in the family-2 reduce the dimensions of the data by 99.31% and achieve 97.98% accuracy. In this example, the integrated tools, VQ/ FPD, accomplished further data compression and less accuracy compared to those reported by FastICA/ 2D DMWT tools. Various experiments and simulations using MATLAB are applied. The experimental results of both families confirm the improvements in the storage requirements, as well as the recognition rates as compared to some recently reported methods.
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Date Issued: 2017
Identifier: CFE0006709, ucf:51878
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006709

Title: Post Conversion Correction of Non-Linear Mismatches for Time Interleaved Analog-to-Digital Converters.
Creator: Parkey, Charna, Mikhael, Wasfy, Qu, Zhihua, Georgiopoulos, Michael, Myers, Brent, Wei, Lei, Chester, David, University of Central Florida
Abstract / Description: Time Interleaved Analog-to-Digital Converters (TI-ADCs) utilize an architecture which enables conversion rates well beyond the capabilities of a single converter while preserving most or all of the other performance characteristics of the converters on which said architecture is based. Most of the approaches discussed here are independent of architecture; some solutions take advantage of specific architectures. Chapter 1 provides the problem formulation and reviews the errors found in ADCs as...
Show moreTime Interleaved Analog-to-Digital Converters (TI-ADCs) utilize an architecture which enables conversion rates well beyond the capabilities of a single converter while preserving most or all of the other performance characteristics of the converters on which said architecture is based. Most of the approaches discussed here are independent of architecture; some solutions take advantage of specific architectures. Chapter 1 provides the problem formulation and reviews the errors found in ADCs as well as a brief literature review of available TI-ADC error correction solutions. Chapter 2 presents the methods and materials used in implementation as well as extend the state of the art for post conversion correction. Chapter 3 presents the simulation results of this work and Chapter 4 concludes the work. The contribution of this research is three fold: A new behavioral model was developed in SimulinkTM and MATLABTM to model and test linear and nonlinear mismatch errors emulating the performance data of actual converters. The details of this model are presented as well as the results of cumulant statistical calculations of the mismatch errors which is followed by the detailed explanation and performance evaluation of the extension developed in this research effort. Leading post conversion correction methods are presented and an extension with derivations is presented. It is shown that the data converter subsystem architecture developed is capable of realizing better performance of those currently reported in the literature while having a more efficient implementation.
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Date Issued: 2015
Identifier: CFE0005683, ucf:50171
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005683

Calibration (3)	+ -
Remote Sensing (3)	+ -
Aquarius (2)	+ -
Carrier Frequency Offset (2)	+ -
DCT (2)	+ -

Efficiency (2)	+ -
Face Recognition (2)	+ -
HIRAD (2)	+ -
ICA (2)	+ -
Independent Component Analysis (2)	+ -
Machine Learning (2)	+ -
Soft Switching (2)	+ -
TMI (2)	+ -
TRMM (2)	+ -
adaptive filter (2)	+ -
brightness temperature (2)	+ -
remote sensing (2)	+ -
(2D)^2PCA (1)	+ -
2DPCA (1)	+ -
Academic (1)	+ -
Academic -- Engineering (1)	+ -
Activities of Daily Living (1)	+ -
Adaptive architectures (1)	+ -
Algorithms (1)	+ -
Along-scan bias (1)	+ -
Amplitude Estimation (1)	+ -
Automatic Target Recognition (1)	+ -
Autonomous recovery (1)	+ -
BaTiO3 (1)	+ -
Big Data Analysis (1)	+ -

Mikhael, Wasfy (50)	+ -
University of Central Florida (49)	+ -
Jones, W Linwood (15)	+ -
Batarseh, Issa (10)	+ -
Kutkut, Nasser (8)	+ -

Wahid, Parveen (8)	+ -
Wei, Lei (8)	+ -
Haralambous, Michael (6)	+ -
Atia, George (5)	+ -
Myers, Brent (4)	+ -
Wilheit, Thomas (4)	+ -
Wu, Xinzhang (4)	+ -
Behal, Aman (3)	+ -
DeMara, Ronald (3)	+ -
Junek, William (3)	+ -
Qu, Zhihua (3)	+ -
Sun, Wei (3)	+ -
Zec, Josko (3)	+ -
Gong, Xun (2)	+ -
Hejazin, Yazan (2)	+ -
Hunter, Matthew (2)	+ -
Jones, W (2)	+ -
Lin, Mingjie (2)	+ -
Lotfifard, Saeed (2)	+ -
Piepmeier, Jeffrey (2)	+ -
Sundaram, Kalpathy (2)	+ -
Vosoughi, Azadeh (2)	+ -
Wu, Thomas (2)	+ -
Yuan, Jiann-Shiun (2)	+ -
ABDELWAHAB, MANAL MAHMOUD (1)	+ -

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