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Articles 1 - 30 of 37
Full-Text Articles in Engineering
A Study Of Equatorial Ionopsheric Variability Using Signal Processing Techniques, Xiaoni Wang
A Study Of Equatorial Ionopsheric Variability Using Signal Processing Techniques, Xiaoni Wang
Electronic Theses and Dissertations
The dependence of equatorial ionosphere on solar irradiances and geomagnetic activity are studied in this dissertation using signal processing techniques. The statistical time series, digital signal processing and wavelet methods are applied to study the ionospheric variations. The ionospheric data used are the Total Electron Content (TEC) and the critical frequency of the F2 layer (foF2). Solar irradiance data are from recent satellites, the Student Nitric Oxide Explorer (SNOE) satellite and the Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite. The Disturbance Storm-Time (Dst) index is used as a proxy of geomagnetic activity in the equatorial region. The results are summarized …
A Comparison And Evaluation Of Common Pid Tuning Methods, Justin Youney
A Comparison And Evaluation Of Common Pid Tuning Methods, Justin Youney
Electronic Theses and Dissertations
The motivation behind this thesis is to consolidate and evaluate the most common Proportional Integral Derivative (PID) controller tuning techniques used in industry. These are the tuning techniques used when the plant transfer function is not known. Many of these systems are poorly tuned because such consolidated information is not easily found in one single source such as this thesis. Once one of the tuning methods are applied almost always there will be further fine tuning needed to bring the system into the required design criteria. The purpose here is to find out which tuning technique will yield the lowest …
An Analysis Of Misclassification Rates For Decision Trees, Mingyu Zhong
An Analysis Of Misclassification Rates For Decision Trees, Mingyu Zhong
Electronic Theses and Dissertations
The decision tree is a well-known methodology for classification and regression. In this dissertation, we focus on the minimization of the misclassification rate for decision tree classifiers. We derive the necessary equations that provide the optimal tree prediction, the estimated risk of the tree's prediction, and the reliability of the tree's risk estimation. We carry out an extensive analysis of the application of Lidstone's law of succession for the estimation of the class probabilities. In contrast to existing research, we not only compute the expected values of the risks but also calculate the corresponding reliability of the risk (measured by …
Simulation And Study Of The Stokes Vector In A Precipitating Atmosphere, Ian Adams
Simulation And Study Of The Stokes Vector In A Precipitating Atmosphere, Ian Adams
Electronic Theses and Dissertations
Precipitation is a dominating quantity in microwave radiometry. The large emission and scattering signals of rain and ice, respectively, introduce large contributions to the measured brightness temperature. While this allows for accurate sensing of precipitation, it also results in degraded performance when retrieving other geophysical parameters, such as near-surface ocean winds. In particular, the retrieval of wind direction requires precise knowledge of polarization, and nonspherical particles can result in a change in the polarization of incident radiation. The aim of this dissertation is to investigate the polarizing effects of precipitation in the atmosphere, including the existence of a precipitation signal …
Estimation Of Oceanic Rainfall Using Passive And Active Measurements From Seawinds Spaceborne Microwave Sensor, Khalil Ali Ahmad
Estimation Of Oceanic Rainfall Using Passive And Active Measurements From Seawinds Spaceborne Microwave Sensor, Khalil Ali Ahmad
Electronic Theses and Dissertations
The Ku band microwave remote sensor, SeaWinds, was developed at the National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL). Two identical SeaWinds instruments were launched into space. The first was flown onboard NASA QuikSCAT satellite which has been orbiting the Earth since June 1999, and the second instrument flew onboard the Japanese Advanced Earth Observing Satellite II (ADEOS-II) from December 2002 till October 2003 when an irrecoverable solar panel failure caused a premature end to the ADEOS-II satellite mission. SeaWinds operates at a frequency of 13.4 GHz, and was originally designed to measure the speed and direction of …
Integrated Topologies And Digital Control For Satellite Power Management And Distribution Systems, Hussam Al-Atrash
Integrated Topologies And Digital Control For Satellite Power Management And Distribution Systems, Hussam Al-Atrash
Electronic Theses and Dissertations
This work is focused on exploring advanced solutions for space power management and distribution (PMAD) systems. As spacecraft power requirements continue to increase, paralleled by the pressures for reducing cost and overall system weight, power electronics engineers will continue to face major redesigns of the space power systems in order to meet such challenges. Front-end PMAD systems, used to interface the solar sources and battery backup to the distribution bus, need to be designed with increased efficiency, reliability, and power density. A new family of integrated single-stage power converter structures is introduced here. This family allows the interface and control …
Discussion On Effective Restoration Of Oral Speech Using Voice Conversion Techniques Based On Gaussian Mixture Modeling, Gustavo Alverio
Discussion On Effective Restoration Of Oral Speech Using Voice Conversion Techniques Based On Gaussian Mixture Modeling, Gustavo Alverio
Electronic Theses and Dissertations
Today's world consists of many ways to communicate information. One of the most effective ways to communicate is through the use of speech. Unfortunately many lose the ability to converse. This in turn leads to a large negative psychological impact. In addition, skills such as lecturing and singing must now be restored via other methods. The usage of text-to-speech synthesis has been a popular resolution of restoring the capability to use oral speech. Text to speech synthesizers convert text into speech. Although text to speech systems are useful, they only allow for few default voice selections that do not represent …
Soft Switching Multi-Resonant Forward Converter Dc To Dc Application For Communications Equipment, David Marlin Bills
Soft Switching Multi-Resonant Forward Converter Dc To Dc Application For Communications Equipment, David Marlin Bills
Electronic Theses and Dissertations
In the field of power electronics there is always a push to create smaller and more efficient power conversion systems. This push is driven by the industry that uses the power systems, and can be realized by new semiconductor devices or new techniques. This examination describes a novel technique for a small and highly efficient method of converting relatively high DC voltage to a very low voltage for use in the telecommunications industry. A modification to the standard Forward Resonant converter results in improvements in component stress, system efficiency, response time, and control circuitry. This examination describes background information needed …
Comparison Of Sparse Coding And Jpeg Coding Schemes For Blurred Retinal Images., Balaji Chandrasekaran
Comparison Of Sparse Coding And Jpeg Coding Schemes For Blurred Retinal Images., Balaji Chandrasekaran
Electronic Theses and Dissertations
Overcomplete representations are currently one of the highly researched areas especially in the field of signal processing due to their strong potential to generate sparse representation of signals. Sparse representation implies that given signal can be represented with components that are only rarely significantly active. It has been strongly argued that the mammalian visual system is highly related towards sparse and overcomplete representations. The primary visual cortex has overcomplete responses in representing an input signal which leads to the use of sparse neuronal activity for further processing. This work investigates the sparse coding with an overcomplete basis set representation which …
Control And Stabilization Of Laser Plasmasources For Euv Lithography, Jose Cunado
Control And Stabilization Of Laser Plasmasources For Euv Lithography, Jose Cunado
Electronic Theses and Dissertations
Extreme Ultraviolet (EUV) sources rely on droplet laser plasmas for EUV generation. These sources consist of a small (30 µm diameter) droplet which is excited into plasma emitting EUV around 13.5 nm, the industry’s chosen wavelength for EUV lithography (EUVL). These sources are the best candidates for the commercialization of EUVL allowing mass production of computer chips with 32 nm or even smaller feature size. However, the biggest challenges which EUV source developers encounter today are the issues of conversion efficiency (CE) and debris. In order to satisfy the technology requirements, the source will need to meet high levels of …
Modeling Of Liquid Crystal Display And Photonic Devices, Zhibing Ge
Modeling Of Liquid Crystal Display And Photonic Devices, Zhibing Ge
Electronic Theses and Dissertations
Liquid crystal (LC) materials have been widely applied in electro-optical devices, among which display is the most successful playground and numerous new applications in photonic areas (such as laser beam steering devices) are also emerging. To well guide the device design for optimum performance, accurate modeling is of prior and practical importance. Generally, the modeling of LC devices includes two parts in sequence: accurate LC molecule deformation extraction under external electric fields and optical calculation thereafter for the corresponding electro-optical behaviors. In this dissertation, first, hybrid finite element method and finite difference method are developed to minimize the free energy …
Novel Facial Image Recognition Techniques Employing Principal Component Analysis, Moataz Mahmoud Abdelwahab
Novel Facial Image Recognition Techniques Employing Principal Component Analysis, Moataz Mahmoud Abdelwahab
Electronic Theses and Dissertations
Recently, pattern recognition/classification has received considerable attention in diverse engineering fields such as biomedical imaging, speaker identification, fingerprint recognition, and face recognition, etc. This study contributes novel techniques for facial image recognition based on the Two dimensional principal component analysis in the transform domain. These algorithms reduce the storage requirements by an order of magnitude and the computational complexity by a factor of 2 while maintaining the excellent recognition accuracy of the recently reported methods. The proposed recognition systems employ different structures, multicriteria and multitransform. In addition, principal component analysis in the transform domain in conjunction with vector quantization is …
High-Intensity Ultra-Fast Laser Interaction Technologies, Robert Thomas Bernath
High-Intensity Ultra-Fast Laser Interaction Technologies, Robert Thomas Bernath
Electronic Theses and Dissertations
To our knowledge this is the first comprehensive study of laser-induced effects generated at intermediate distances using self-channeled femtosecond laser pulses. Studies performed were made both experimentally and theoretically with the use of novel modeling techniques. Peak laser pulse powers above 3 GW allow beam propagation without divergence for up to several kilometers. In this regime, experiments were performed at 30 meters from the laser system in a custom propagation and target range, utilizing the Laser Plasma Laboratory's Terawatt laser system. Experiments included investigations of laser ablation; electromagnetic pulsed (EMP) radiation generation over the 1-18 GHz region; shockwave formation in …
Steady State And Dynamic Analysis And Optimization Of Single-Stage Power Factor Correction Converters, Khalid Rustom
Steady State And Dynamic Analysis And Optimization Of Single-Stage Power Factor Correction Converters, Khalid Rustom
Electronic Theses and Dissertations
With the increased interest in applying Power Factor Correction (PFC) to off-line AC-DC converters, the field of integrated, single-stage PFC converter development has attracted wide attention. Considering the tens of millions of low-to-medium power supplies manufactured each year for today's rechargeable equipment, the expected reduction in cost by utilizing advanced technologies is significant. To date, only a few single-stage topologies have made it to the market due to the inherit limitations in this structure. The high voltage and current stresses on the components led to reduced efficiency and an increased failure rate. In addition, the component prices tend to increase …
Hot Carrier Effect On Ldmos Transistors, Liangjun Jiang
Hot Carrier Effect On Ldmos Transistors, Liangjun Jiang
Electronic Theses and Dissertations
One of the main problems encountered when scaling down is the hot carrier induced degradation of MOSFETs. This problem has been studied intensively during the past decade, under both static and dynamic stress conditions. In this period it has evolved from a more or less academic research topic to one of the most stringent constraints guaranteeing the lifetime of sub-micron devices. New drain engineering technique leads to the extensive usage of lateral doped drain structures. In these devices the peak of the lateral field is lowered by reducing the doping concentration near the drain and by providing a smooth junction …
A Virtual Reality Visualization Ofan Analytical Solution Tomobile Robot Trajectory Generationin The Presence Of Moving Obstacles, Ricardo Elias
A Virtual Reality Visualization Ofan Analytical Solution Tomobile Robot Trajectory Generationin The Presence Of Moving Obstacles, Ricardo Elias
Electronic Theses and Dissertations
Virtual visualization of mobile robot analytical trajectories while avoiding moving obstacles is presented in this thesis as a very helpful technique to properly display and communicate simulation results. Analytical solutions to the path planning problem of mobile robots in the presence of obstacles and a dynamically changing environment have been presented in the current robotics and controls literature. These techniques have been demonstrated using two-dimensional graphical representation of simulation results. In this thesis, the analytical solution published by Dr. Zhihua Qu in December 2004 is used and simulated using a virtual visualization tool called VRML.
Ultra-Wideband Orthogonal Frequency Coded Saw Correlators, Daniel Gallagher
Ultra-Wideband Orthogonal Frequency Coded Saw Correlators, Daniel Gallagher
Electronic Theses and Dissertations
Ultra-wideband (UWB) communication new technology with ability to share the FCC allocated frequency spectrum, large channel capacity and data rate, simple transceiver architecture and high performance in noisy environments. Such communication advantages have paved the way for emerging wireless technologies such as wireless high definition video streaming, wireless sensor networks and more. This thesis examines orthogonal frequency coded surface acoustic wave (SAW) correlators for use in advanced UWB communication systems. Orthogonal frequency coding (OFC) and pseudo-noise (PN) coding provides a means for UWB spreading of data. The use of OFC spectrally spreads a PN sequence beyond that of CDMA because …
Signal Processing Of An Ecg Signal In The Presence Of A Strong Static Magnetic Field, Aditya Gupta
Signal Processing Of An Ecg Signal In The Presence Of A Strong Static Magnetic Field, Aditya Gupta
Electronic Theses and Dissertations
This dissertation addresses the problem of elevation of the T wave of an electrocardiogram (ECG) signal in the magnetic resonance imaging (MRI). In the MRI, due to the strong static magnetic field the interaction of the blood flow with this strong magnetic field induces a voltage in the body. This voltage appears as a superimposition at the locus of the T wave of the ECG signal. This looses important information required by the doctors to interpret the ST segment of the ECG and detect diseases such as myocardial infarction. This dissertation aims at finding a solution to the problem of …
Investigation Of Pn Junction Delineation Resolution Using Electron Beam Induced Current, Christopher Hayden Hontgas
Investigation Of Pn Junction Delineation Resolution Using Electron Beam Induced Current, Christopher Hayden Hontgas
Electronic Theses and Dissertations
This dissertation will investigate electron beam induced current (EBIC) for determining semiconductor material and device parameters. While previous experimental work on PN junction delineation using EBIC with the scanning electron microscope has resulted in resolution to approximately 10 nm, theoretical study shows the potential use of EBIC for higher resolution (nanometer) PN junction and FET channel length delineation using the transmission electron microscope. Theoretical arguments using computer simulations of electron beam generation volume, collection probability and EBIC were performed and are presented for the purpose of determining EBIC use in a 300 keV transmission electron microscope (TEM) for PN junction …
Comparison Of Single Stage And Two Stage Stage Grid-Tie Inverters, Keith Mansfield
Comparison Of Single Stage And Two Stage Stage Grid-Tie Inverters, Keith Mansfield
Electronic Theses and Dissertations
This thesis compares two methods of designing grid-tie inverters. The first design topology is a traditional two stage approach consisting of an isolated DC-DC converter on the input followed by a high switching frequency SPWM (Sinusoidal Pulse Width Modulation) stage to produce the required low frequency sine wave output. The novel second design approach employs a similar DC-DC input stage capable of being modulated to provide a rectified sine wave output voltage/current waveform. This stage is followed by a simple low frequency switched Unfolding Stage to recreate the required sine wave output. Both of the above designs have advantages and …
Investigation Of Reactively Sputtered Silicon Carbon Boron Nitride (Sicbn) Thin Films For High Temperature Applications, Arun Vijayakumar
Investigation Of Reactively Sputtered Silicon Carbon Boron Nitride (Sicbn) Thin Films For High Temperature Applications, Arun Vijayakumar
Electronic Theses and Dissertations
The increasing demand for efficient energy systems in the last decade has brought about the development of advanced sensor systems that utilize advance detection methods to help in preventive maintenance of these essential systems. These usually are needed in hard to access environments where conditions are extreme and unfit for human interaction. Thin film based sensors deposited directly on the surfaces exposed to harsh environments can serve as ideal means of measuring the temperature of the component during operation. They provide the basic advantage of proximity to the surface and hence accurate measurement of the surface temperature. The low mass …
Modeling And Digital Control Of High Frequency Dc-Dc Power Converters, Yangyang Wen
Modeling And Digital Control Of High Frequency Dc-Dc Power Converters, Yangyang Wen
Electronic Theses and Dissertations
The power requirements for leading edge digital integrated circuits have become increasingly demanding. Power converter systems must be faster, more flexible, more precisely controllable and easily monitored. Meanwhile, in addition to control process, the new functions such as power sequencing, communication with other systems, voltage dynamic programming,load line specifications, phase current balance, protection, power status monitoring and system diagnosis are going into today's power supply systems. Digital controllers, compared withanalog controllers, are in a favorable position to provide basic feedback control as well as those power management functions with lower cost and great flexibility. The dissertation gives an overview of …
High Current Density Low Voltage Isolated Dc-Dc Converterswith Fast Transient Response, Liangbin Yao
High Current Density Low Voltage Isolated Dc-Dc Converterswith Fast Transient Response, Liangbin Yao
Electronic Theses and Dissertations
With the rapid development of microprocessor and semiconductor technology, industry continues to update the requirements for power supplies. For telecommunication and computing system applications, power supplies require increasing current level while the supply voltage keeps decreasing. For example, the Intel's CPU core voltage decreased from 2 volt in 1999 to 1 volt in 2005 while the supply current increased from 20A in 1999 to up to 100A in 2005. As a result, low-voltage high-current high efficiency dc-dc converters with high power-density are demanded for state-of-the-art applications and also the future applications. Half-bridge dc-dc converter with current-doubler rectification is regarded as …
Advanced Coding And Modulation For Ultra-Wideband And Impulsive Noises, Libo Yang
Advanced Coding And Modulation For Ultra-Wideband And Impulsive Noises, Libo Yang
Electronic Theses and Dissertations
The ever-growing demand for higher quality and faster multimedia content delivery over short distances in home environments drives the quest for higher data rates in wireless personal area networks (WPANs). One of the candidate IEEE 802.15.3a WPAN proposals support data rates up to 480 Mbps by using punctured convolutional codes with quadrature phase shift keying (QPSK) modulation for a multi-band orthogonal frequency-division multiplexing (MB-OFDM) system over ultra wideband (UWB) channels. In the first part of this dissertation, we combine more powerful near-Shannon-limit turbo codes with bandwidth efficient trellis coded modulation, i.e., turbo trellis coded modulation (TTCM), to further improve the …
Anchoring Energy And Pretilt Angle Effects On Liquid Crystal Response Time, Xiangyi Nie
Anchoring Energy And Pretilt Angle Effects On Liquid Crystal Response Time, Xiangyi Nie
Electronic Theses and Dissertations
This dissertation covers some important topics on the liquid crystal-substrate surface effects, including theoretical derivations and confirming experimental results. The research work is expected to make important impacts on liquid crystal device designs and to open new doors for further research along these topics. In this dissertation, a novel high-electric-field technique is developed to characterize the anchoring energy of vertically-aligned liquid crystal cells. Both theoretical analyses and confirming experimental results are presented. Vertically-aligned liquid crystal cells with buffed polyimide alignment layers are used to validate the measurement techniques. Based on the voltage-dependent transmittance of the liquid crystal cells, a linear …
Evaluation Of The Amazon Rain Forest As A Distributed Target For Satellite Microwave Radiometer Calibration, Nishant Patel
Evaluation Of The Amazon Rain Forest As A Distributed Target For Satellite Microwave Radiometer Calibration, Nishant Patel
Electronic Theses and Dissertations
For over three decades, satellite radars have used the Amazon tropical rain forest as a stable homogeneous and isotropic scattering target for calibration. This thesis extends previous work to consider the use of the Amazon as a blackbody target for passive microwave inter-satellite calibration. The characterization of a natural target for radiometric calibration is a formidable task due to the difficulty in obtaining an absolute brightness temperature standard. Previously, multi-frequency microwave brightness temperatures measured by the Tropical Rainfall Measuring Mission Microwave Imager (TMI) were used to provide multi-year observations in local time windows. Our approach differs in that we will …
Design And Modeling Of Radiation Hardened Ldmosfet For Space Craft Power Systems, Patrick Shea
Design And Modeling Of Radiation Hardened Ldmosfet For Space Craft Power Systems, Patrick Shea
Electronic Theses and Dissertations
NASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching performance, development and manufacturing costs, and total mass of power electronics systems. Availability of a hardened fast-switching power MOSFET will allow space-borne power electronics to approach the current level of terrestrial …
Gate Stack And Channel Engineering: Study Of Metal Gates And Ge Channel Devices, Ravi Todi
Gate Stack And Channel Engineering: Study Of Metal Gates And Ge Channel Devices, Ravi Todi
Electronic Theses and Dissertations
The continued scaling of device dimensions in complementary metal oxide semiconductor (CMOS) technology within the sub-100 nm region requires an alternative high dielectric constant (high-k) oxide layer to counter high tunneling leakage currents, a metallic gate electrode to address polysilicon depletion, boron penetration and high polysilicon sheet resistance, and high mobility channel materials to boost the CMOS performance. Metal gates can also offer improved thermal and chemical stability, but their use requires that we improve our understanding of how the metal alloy phase, crystallographic orientation, and composition affect the electronic properties of the metal alloy-oxide interface. To replace n++ and …
Modeling And Analysis Of The Eds Maglev System With The Halbach Magnet Array, Wonsuk Ko
Modeling And Analysis Of The Eds Maglev System With The Halbach Magnet Array, Wonsuk Ko
Electronic Theses and Dissertations
The magnetic field analysis based on the wavelet transform is performed. The Halbach array magnetic field analysis has been studied using many methods such as magnetic scalar potential, magnetic vector potential, Fourier analysis and Finite Element Methods. But these analyses cannot identify a transient oscillation at the beginning stage of levitation. The wavelet transform is used for analyzing the transient oscillatory response of an EDS Maglev system. The proposed scheme explains the under-damped dynamics that results from the cradle's dynamic response to the irregular distribution of the magnetic field. It suggests this EDS Maglev system that responds to a vertical …
Knowledge Based Measurement Of Enhancing Brain Tissue In Anisotropic Mr Imagery, Eric Leach
Knowledge Based Measurement Of Enhancing Brain Tissue In Anisotropic Mr Imagery, Eric Leach
Electronic Theses and Dissertations
Medical Image Analysis has emerged as an important field in the computer vision community. In this thesis, two important issues in medical imaging are addressed and a solution for each is derived and synergistically combined as one coherent system. Firstly, a novel approach is proposed for High Resolution Volume (HRV) construction by combining different frequency components at multiple levels, which are separated by using a multi-resolution pyramid structure. Current clinical imaging protocols make use of multiple orthogonal low resolution scans to measure the size of the tumor. The highly anisotropic data result in difficulty and even errors in tumor assessment. …