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Articles 1 - 30 of 53
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 …
Magnetics Design For High Current Low Voltage Dc/Dc Converter, Hua Zhou
Magnetics Design For High Current Low Voltage Dc/Dc Converter, Hua Zhou
Electronic Theses and Dissertations
With the increasing demand for small and cost efficient DC/DC converters, the power converters are expected to operate with high efficiency. Magnetics components design is one of the biggest challenges in achieving the higher power density and higher efficiency due to the significant portion of magnetics components volume in the whole power system. At the same time, most of the experimental phenomena are related to the magnetics components. So, good magnetics components design is one of the key issues to implement low voltage high current DC/DC converter. Planar technology has many advantages. It has low profile construction, low leakage inductance …
Optimization Of Zonal Wavefront Estimation And Curvature Measurements, Weiyao Zou
Optimization Of Zonal Wavefront Estimation And Curvature Measurements, Weiyao Zou
Electronic Theses and Dissertations
Optical testing in adverse environments, ophthalmology and applications where characterization by curvature is leveraged all have a common goal: accurately estimate wavefront shape. This dissertation investigates wavefront sensing techniques as applied to optical testing based on gradient and curvature measurements. Wavefront sensing involves the ability to accurately estimate shape over any aperture geometry, which requires establishing a sampling grid and estimation scheme, quantifying estimation errors caused by measurement noise propagation, and designing an instrument with sufficient accuracy and sensitivity for the application. Starting with gradient-based wavefront sensing, a zonal least-squares wavefront estimation algorithm for any irregular pupil shape and size …
Entire Load Efficiency And Dynamic Performance Improvements For Dc-Dc Converters, Osama Abdel-Rahman
Entire Load Efficiency And Dynamic Performance Improvements For Dc-Dc Converters, Osama Abdel-Rahman
Electronic Theses and Dissertations
The scope of this work can be summarized by three main aspects of DC-DC power converters. The first aspect is soft switching topologies to improve conversion efficiency for On-Board Converters or Point of load (POL) converters, the second aspect is load adaptive control techniques to improve all load efficiency for battery powered DC-DC converters that are applied to mobile devices, and the third aspect is dynamic performance improvement techniques to improve load transient in voltage regulators. Topologies and control techniques for DC-DC converters are presented after reviewing loads powering requirements and steady-state and transients design challenges.
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 …
All-Optical Regeneration For Phase-Shift Keyed Optical Communication Systems, Kevin Croussore
All-Optical Regeneration For Phase-Shift Keyed Optical Communication Systems, Kevin Croussore
Electronic Theses and Dissertations
All-optical signal processing techniques for phase-shift keyed (PSK) systems were developed theoretically and demonstrated experimentally. Nonlinear optical effects in fibers, in particular four-wave mixing (FWM) that occurs via the ultra-fast Kerr nonlinearity, offer a flexible framework within which numerous signal processing functions can be accomplished. This research has focused on the regenerative capabilities of various FWM configurations in the context of processing PSK signals. Phase-preserving amplitude regeneration, phase regeneration, and phase-regenerative wavelength conversion are analyzed and demonstrated experimentally. The single-pump phase-conjugation process was used to regenerate RZ-DPSK pulse amplitudes with different input noise distributions, and the impact on output phase …
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 …
Efficient Algorithms For Correlation Pattern Recognition, Pradeep Ragothaman
Efficient Algorithms For Correlation Pattern Recognition, Pradeep Ragothaman
Electronic Theses and Dissertations
The mathematical operation of correlation is a very simple concept, yet has a very rich history of application in a variety of engineering fields. It is essentially nothing but a technique to measure if and to what degree two signals match each other. Since this is a very basic and universal task in a wide variety of fields such as signal processing, communications, computer vision etc., it has been an important tool. The field of pattern recognition often deals with the task of analyzing signals or useful information from signals and classifying them into classes. Very often, these classes are …
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 …
Effects Of Polarization And Coherence On The Propagation And The Detection Of Stochastic Electromagnetic Beams, Mohamed Fouad Salem
Effects Of Polarization And Coherence On The Propagation And The Detection Of Stochastic Electromagnetic Beams, Mohamed Fouad Salem
Electronic Theses and Dissertations
Most of the physically realizable optical sources are radiating in a random manner given the random nature of the radiation of a large number of atoms that constitute the source. Besides, a lot of natural and synthetic materials are fluctuating randomly. Hence, the optical fields that one encounters, in most of the applications are fluctuating and must be treated using random or stochastic functions. Within the framework of the scalar-coherence theory, one can describe changes of the properties of any stochastic field such as the spectral density and the spectral degree of coherence on propagation in any linear medium, deterministic …
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 …
Two-Dimensional Guided Mode Resonant Structures For Spectral Filtering Applications, Sakoolkan Boonruang
Two-Dimensional Guided Mode Resonant Structures For Spectral Filtering Applications, Sakoolkan Boonruang
Electronic Theses and Dissertations
Guided mode resonant (GMR) structures are optical devices that consist of a planar waveguide with a periodic structure either imbedded in or on the surface of the structure. The resonance anomaly in GMR structures has many applications as dielectric mirrors, tunable devices, sensors,and narrow spectral band reflection filters. A desirable response from a resonant grating filter normally includes a nearly 100% narrowband resonant spectral reflection (transmission), and a broad angular acceptance at either normal incidence or an oblique angle of incidence. This dissertation is a detailed study of the unique nature of the resonance anomaly in GMR structures with two-dimensional …
Scalable Volumetric Three-Dimensional Up-Conversion Display Medium, Jung-Hyun Cho
Scalable Volumetric Three-Dimensional Up-Conversion Display Medium, Jung-Hyun Cho
Electronic Theses and Dissertations
There are many different techniques to display 3D information. However, not many of them are able to provide sufficient depth cues to the observers to sense or feel the images as real three-dimensional objects. Volumetric three-dimensional displays generate images within a real 3D space, so they provide most of the depth cues automatically. This thesis discusses the basic notions required to understand three-dimensional displays. Also discussed are different techniques used to display 3D information and their advantages and disadvantages as well as their current limitations. Several rare-earth doped fluoride crystals that are excited to emit visible light by sequential two …
Process Development For The Fabrication Of Mesoscale Electrostatic Valve Assembly, Shailini Rajiv Dhru
Process Development For The Fabrication Of Mesoscale Electrostatic Valve Assembly, Shailini Rajiv Dhru
Electronic Theses and Dissertations
This study concentrates on two of the main processes involved in the fabrication of electrostatic valve assembly, thick resist photolithography and wet chemical etching of a polyamide film. The electrostatic valve has different orifice diameters of 25, 50, 75 and 100 µm. These orifice holes are to be etched in the silicon wafer with deep reactive ion etching. The photolithography process is developed to build a mask of 15 µm thick resist pattern on silicon wafer. This photo layer acts as a mask for deep reactive ion etching. Wet chemical etching process is developed to etch kapton polyamide film. This …
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 …
High-Speed Modelocked Semiconductor Lasers And Applications In Coherent Photonic Systems, Wangkuen Lee
High-Speed Modelocked Semiconductor Lasers And Applications In Coherent Photonic Systems, Wangkuen Lee
Electronic Theses and Dissertations
1.55-µm high-speed modelocked semiconductor lasers are theoretically and experimentally studied for various coherent photonic system applications. The modelocked semiconductor lasers (MSLs) are designed with high-speed (>5 GHz) external cavity configurations utilizing monolithic two-section curved semiconductor optical amplifiers. By exploiting the saturable absorber section of the monolithic device, passive or hybrid mode-locking techniques are used to generate short optical pulses with broadband optical frequency combs. Laser frequency stability is improved by applying the Pound-Drever-Hall (PDH) frequency stabilization technique to the MSLs. The improved laser performance after the frequency stabilization (a frequency drifting of less than 350 MHz), is extensively studied …
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 …