Electrical and Computer Engineering Commons^™

Multi-Modal Enhancement Techniques For Visibility Improvement Of Digital Images, Li Tao

Electrical & Computer Engineering Theses & Dissertations

Image enhancement techniques for visibility improvement of 8-bit color digital images based on spatial domain, wavelet transform domain, and multiple image fusion approaches are investigated in this dissertation research.

In the category of spatial domain approach, two enhancement algorithms are developed to deal with problems associated with images captured from scenes with high dynamic ranges. The first technique is based on an illuminance-reflectance (I-R) model of the scene irradiance. The dynamic range compression of the input image is achieved by a nonlinear transformation of the estimated illuminance based on a windowed inverse sigmoid transfer function. A single-scale neighborhood dependent contrast …

Melting And Solidification Study Of Indium And Bismuth Nanocrystals Using Reflection High-Energy Electron Diffraction, Mohamed K. Zayed

Electrical & Computer Engineering Theses & Dissertations

As technology begins to utilize nanocrystals for many chemical, biological, medical, electrical, and optoelectrical applications, there is a growing need for an understanding of their fundamental properties. The study of melting and solidification of nanocrystals is of interest to fundamental understanding of the effect of reduced size and crystal shape on the solid-liquid phase transition. Melting and solidification of as-deposited and recrystallized indium and bismuth nanocrystals were studied using reflection high-energy electron diffraction (RHEED). The nanocrystals were thermally deposited on highly oriented 002-graphite substrate at different deposition temperatures. The growth dynamics of the nanocrystals was studied using in situ RHEED …

Modeling And Simulation Of Photonic Crystal Fibers Using Finite Difference Frequency Domain Method, Md. Khalid Ikram

Electrical & Computer Engineering Theses & Dissertations

Photonic crystal fibers (PCFs) allow guiding light in low-index core. These fibers exhibit properties such as single-mode operation in broad wavelength region. The mode shape and group velocity dispersion can be controlled by designing the microstructures of the cladding. In order to study these properties, a fast, efficient, and highly accurate numerical modeling method is required.

A full-vectorial finite-difference frequency-domain (FDFD) method is implemented. The modal properties of conventional step index fiber and index-guiding PCF are analyzed using this modeling technique. Compared to plane wave expansion and biorthogonal basis methods, FDFD is found to be simple, reliable, and efficient. PCFs …

Hierarchical Hybrid Multicast An End System Multicast Algorithm Approach, Guillermo Loaisiga

Electrical & Computer Engineering Theses & Dissertations

Due to the rapid development in the computer and communication technologies, the Internet is experiencing an increasing demand of high-speed, real-time distributed applications, such as live streaming multimedia, videoconferencing, distributed simulations, and multiparty games. Multicast is an efficient transmission mechanism to support these applications. Historically, IP Multicast (IPM) has provided multicast support with well-known benefits, especially in bandwidth savings. However, it has experienced little deployment due to economic and architectural limitations.

Overlay multicast holds promise for the implementation of large scale Internet multicast services. An overlay network is a virtual topology constructed on top of the Internet infrastructure. This concept …

Huffman Approach To Opcode Compression, Jason B. Shreve

Electrical & Computer Engineering Theses & Dissertations

Instructions are the building blocks of computer programs. They are composed of opcodes, which uniquely identify each instruction, and the operands or data. In most architectures, the instruction length is a set multiple of the word size. The size and number of operands vary by instruction. Due to programmer usage, program need, or compiler design, opcodes do not occur with a constant distribution. Likely, some opcodes occur very frequently, whereas others occur very infrequently or not at all. If the length of an opcode were representative of its frequency, compression in program size might be achieved.

This thesis is an …

Modeling Nerve Electro-Stimulation In The Nanosecond Regime, Feng Chen

Electrical & Computer Engineering Theses & Dissertations

Numerical simulations of electrical stimulation of frog gastrocnemius muscles have been carried out for pulse durations in the nanosecond regime. There are a number of potential advantages in using ultra-short pulses for neural stimulation, and no previous electro-stimulation work in the sub-microsecond regime has been reported. A timedependent, three-dimensional analysis model was developed and implemented for three distinct situations: (i) direct stimulation via electrode contact, (ii) indirect excitation based on electrodes immersed in a saline-filled bath, and (iii) remote electromagnetic stimulation through vacuum. The simulations yielded strength-dm ation (S-D) curves with pulse durations as short as 5 ns. Good agreement …

Real-Time Measurements On The Effects Of Ultra-Short High Voltage Pulses On Hl-60 Cells, Michalis C. Artemiou

Electrical & Computer Engineering Theses & Dissertations

The application of high voltage microsecond pulses that are above a critical value, to biological cells, has been shown to cause electroporation (Neumann, 1989). In addition, ultra-short pulses of several tens to hundreds of nanoseconds duration have been recently shown to affect intracellular structures without disturbing the plasma membrane (Schoenbach, 2001). However, such ultra-short intense pulses are expected to cause deformation of cells due to Maxwell stresses. This deformation was studied by means of an imaging technique with 10 ns temporal resolution on HL-60 cells. The imaging system consists of an inverted microscope where a spark light source was used …

Dynamical Studies Of Model Membrane And Cellular Response To Nanosecond, High-Intensity Pulsed Electric Fields, Qin Hu

Electrical & Computer Engineering Theses & Dissertations

The dynamics of electroporation of biological cells subjected to nanosecond, high intensity pulses are studied based on a coupled scheme involving the current continuity and Smoluchowski equations. The improved pore formation energy model includes a dependence on pore population and density. It also allows for variable surface tension and incorporates the effects of finite conductivity on the electrostatic correction term, which was not considered by the simple energy models in the literature. It is shown that E(r) becomes self-adjusting with variations in its magnitude and profile. The whole scheme is self-consistent and dynamic.

An electromechanical analysis based on thin-shell theory …

Stability Analysis Of Jump-Linear Systems Driven By Finite-State Machines With Markovian Inputs, Sudarshan S. Patilkulkarni

Electrical & Computer Engineering Theses & Dissertations

A control system with a fault recovery mechanism in the feedback loop and with faults occurring in a non-deterministic manner can be modeled as a class of hybrid systems, i.e., a dynamical system switched by a finite-state machine or an automaton. When the plant and controller are linear, such a system can be modeled as a jump-linear system driven by a finite-state machine with a random input process. Such fault recovery mechanisms are found in flight control systems and distributed control systems with communication networks. In these critical applications, closed-loop stability of the system in the presence of fault recoveries …

Fuzzy Modeling Of Electromagnetic Emissions From Portable Electronic Devices Onboard Commercial Aircraft, Madiha Jamil Jafri

Electrical & Computer Engineering Theses & Dissertations

The use of Portable Electronic Devices (PEDs) is prohibited during take-off and landing of an aircraft because PEDs may emit signals that can interfere with the aircraft's navigation and communication systems. The electromagnetic interference (EMI) on the aircraft's electronics due to PEDs emissions is examined for Boeing 737 and 747 aircraft. This work, funded by the NASA Graduate Researchers Program, uses Interference Path Loss (IPL) data, collected by researchers from NASA Langley Research Center, Eagles Wings Inc. and United Airlines on several out-of-service United B737 and B747 airplanes.

B737 and B747 IPL data has been analyzed using a graphical analysis …

Generating Series For Interconnected Nonlinear Systems And The Formal Laplace-Borel Transform, Yaqin Li

Electrical & Computer Engineering Theses & Dissertations

Formal power series methods provide effective tools for nonlinear system analysis. For a broad range of analytic nonlinear systems, their input-output mapping can be described by a Fliess operator associated with a formal power series. In this dissertation, the inter connection of two Fliess operators is characterized by the generating series of the composite system. In addition, the formal Laplace-Borel transform of a Fliess operator is defined and its fundamental properties are presented. The formal Laplace-Borel transform produces an elegant description of system interconnections in a purely algebraic context.

Specifically, four basic interconnections of Fliess operators are addressed: the parallel, …

Scaling And Characterization Of Direct Current Glow Discharge Plasma In Atmospheric Air, Abdel-Aleam Hefney Mohamed

Electrical & Computer Engineering Theses & Dissertations

A microhollow cathode discharge was used as a plasma cathode to sustain a stable direct current glow discharge in atmospheric pressure air. The volumetric scale of glow discharge increased from the millimeter to the centimeter range by extending the plasma in lateral and axial directions. In the axial direction, the length of the glow discharge column was varied from 1 mm to 2 cm, with the sustaining voltage increasing linearly with the glow discharge column length. Extension in the lateral direction was obtained by operating discharges in parallel. The glow discharge plasma of the parallel discharge columns was found to …

Microdischarge Arrays, Wenhui Shi

Electrical & Computer Engineering Theses & Dissertations

Microhollow cathode discharges (MHCDs) are DC or pulsed gas discharges between two electrodes, separated by a dielectric, and containing a concentric hole. The diameter of the hole, in this hollow cathode configuration, is in the hundred-micrometer range. MHCDs satisfy the two conditions necessary for an efficient excimer radiation sources: (1) high energy electrons which are required to provide a high concentration of excited or ionized rare gas atoms; (2) high pressure operation which favors excimer formation (a three-body process). Flat panel excimer sources require parallel operation of MHCDs. Based on the current-voltage characteristics of MHCD discharges, which have positive slopes …

Speaker Normalization For Improved Automatic Speech Recognition For Digital Libraries, Wei Wang

Electrical & Computer Engineering Theses & Dissertations

The context of this thesis work is the improvement of automatic speech recognition (ASR) for use with digital libraries. First, commonly used multimedia file formats and codecs are surveyed with the objective of identifying those formats that preserve speech quality while keeping file sizes compact. The main contribution of the work is a new technique for speaker adaptation based on frequency scale modifications. The frequency scale is modified using a minimum mean square error matching of a spectral template for each speaker to a "typical speaker" spectral template. Each spectral template is computed from the average amplitude-normalized spectra of several …

Electrical Breakdown In Polar Liquids, Shu Xiao

Electrical & Computer Engineering Theses & Dissertations

Hydrodynamic processes following the electrical breakdown in polar liquids, mainly water and propylene carbonate, are studied with electrical pulse-probe systems and optical diagnostics including shadowgraphy and Schlieren techniques. The dielectric strength of water in a repetitively pulsed power system is found to be 750 kV/cm and 650 kV/cm for pulses of 200 nanosecond and 8 microsecond duration, respectively. For energies less than 1 J, the discharge plasma decays in approximately one microsecond. The mechanical effect created by the expanding plasma is a shock wave which has an initial pressure of 1 GPa and decays within approximately 5 microseconds. The observed …

A Computer-Based Articulation Training Aid For Short Words (Cata), Mukund Devarajan

Electrical & Computer Engineering Theses & Dissertations

Several improvements in the vowel articulation training aid (VATA) are described, as well as the efforts to extend the visual feedback system to operate with short words in the form of consonant, vowel and consonant (CVC). The extended version of the visual feedback system is referred to as CATA (Computer-based Articulation Training Aid); the vowel version of the aid (VATA) only operates with ten American English monopthong vowels. Improvements in VATA include the use of a neural network (NN) recognizer method to prune a large database of vowel recordings to eliminate noisy and/or mispronounced tokens. The spectral jitter problem, previously …

Time Domain Dielectric Spectroscopy Analysis Of Hl-60 Cell Suspensions After Microsecond And Submicrosecond Pulsed Electric Fields, Allen Laurence Garner

Electrical & Computer Engineering Theses & Dissertations

Pulsed electric fields (PEF's) above a certain voltage threshold cause electroporation for microsecond pulses and intracellular effects for submicrosecond pulses. Models describing these effects often depend on the electrical properties of the cell, which are altered by the PEF. Time domain dielectric spectroscopy was used to provide data for these models and to measure changes in the conductivity of HL-60 cell suspensions due to single 50 μs and 10 ns PEF's of the same energy. For 1.1 kV/cm, 50 μs pulses, the conductivity rose within a minute after the pulse and dropped dramatically approximately forty minutes after the pulse. For …

Unidirectional Cordic For Efficient Computation Of Trigonometric And Hyperbolic Functions, Satish Ravichandran

Electrical & Computer Engineering Theses & Dissertations

CORDIC (Coordinate Rotation Digital Computer) is an iterative algorithm to compute values of trigonometric, logarithmic and transcendental functions by performing vector rotations, which can be implemented with only shift and add operations in a digital system. CORDIC algorithms are extensively used in the areas of digital signal processing, digital image processing and artificial neural networks. A new technique, named unidirectional CORDIC, for efficient computation of trigonometric and hyperbolic functions is presented in this thesis. In the conventional CORDIC algorithm, the vector rotations are performed in both clockwise and counterclockwise directions, but in the unidirectional CORDIC the vectors are rotated only …

Atmospheric Water Vapor Lidar Measurements Using Analog And Photon Counting Techniques, Anuj Maheshkumar Shah

Electrical & Computer Engineering Theses & Dissertations

Atmospheric water vapor measurements are essential for the understanding of Earth's weather and radiation budget, along with the water cycle. The remote sensing Differential Absorption Lidar (DIAL) technique is a commanding method used for water vapor measurements from aircraft, spaceborne, and ground-based platforms. The new unmanned aerial vehicle (UAV) water vapor DIAL system provides great feasibility due to the weight and size limitations. The system has significantly less weight, power consumption, and noise presence, thus making it great for UAV applications.

This thesis discusses a UAV water vapor DIAL system that was designed, developed, and evaluated. The research effort was …

Photonic Crystals: Modeling And Simulation, Shangping Guo

Electrical & Computer Engineering Theses & Dissertations

Photonic crystals are periodic electromagnetic media in optical wavelength scale. They possess photonic band gaps (PBGs) that inhibit the existence of light within the crystals in certain wavelength range. Such band gaps produce many interesting optical phenomena. In this dissertation, the frequency (plane wave method, PWM) and time domain (finite difference time domain method, FDTD) methods are developed for their modeling and simulation.

The theory and algorithm of plane wave method are studied in detail and implemented in a unique and efficient approach. PWM is used to obtain the gap and mode information of ideal and defective photonic crystals. Several …

Monte Carlo Analysis Of Millimeter-Wave Gan Based Gunn Effect Oscillators, Sridhara Viswanadham

Electrical & Computer Engineering Theses & Dissertations

Gunn diodes are one of the most common high frequency solid-state oscillators at the present time, and are considered as promising devices for millimeter and submillimeter wave applications. Monte Carlo studies of Gunn diodes based on bulk wurtzite GaN have been carried out in this thesis research. Two structures have been examined: (i) devices with conventional single notch structure and (ii) repetitive structures with serial segments to fashion a "multiple domain" device. Wurtzite GaN has been chosen because of the high drift velocity and because analytical expressions for the band structure have recently become available. Performance parameters of interest such …

Fuzzy System Identification Based Upon A Novel Approach To Nonlinear Optimization, Raymond Scott Starsman

Electrical & Computer Engineering Theses & Dissertations

Fuzzy systems are often used to model the behavior of nonlinear dynamical systems in process control industries because the model is linguistic in nature, uses a natural-language rule set, and because they can be included in control laws that meet the design goals. However, because the rigorous study of fuzzy logic is relatively recent, there is a shortage of well-defined and understood mechanisms for the design of a fuzzy system. One of the greatest challenges in fuzzy modeling is to determine a suitable structure, parameters, and rules that minimize an appropriately chosen error between the fuzzy system, a mathematical model, …

A Combinatorial Technique For Face Detection Based On Color And Statistical Analysis, Harishwaran Hariharan

Electrical & Computer Engineering Theses & Dissertations

Automatic detection of faces from video sequences is an important task in security applications. The number, location, size and orientation of human faces in a video frame are unpredictable and can vary from frame to frame. A face detection algorithm for color images in the presence of varying lighting conditions and complexity in background relying upon color and statistical analysis is presented in this thesis. The new method detects skin regions over the entire image and then classifies the skin regions as faces and non-faces. Segmentation of skin regions is performed by a novel color space merging procedure named Integrated …

Parallel Implementation Of A Face Recognition [Sic] System Based On Modular Pca Approach, Rajkiran Gottumukkal

Electrical & Computer Engineering Theses & Dissertations

This thesis describes research in automated methods for the recognition of human faces. The research is driven by the need to design a method, which would ensure high accuracy under the conditions of facial expression, illumination and pose variations. The resulting method is able to cope with uncontrolled nature of facial expression, illumination and head rotations. The main novelty of this work is the idea that some of the local facial features do not vary even when the facial expression, illumination and pose vary. This idea is applied to the existing principle component analysis lPCA) method to arrive at a …

A Pipelined Architecture For Real Time Correction Of Barrel Distortion In Wide-Angle Camera Images, Hau Trung Ngo

Electrical & Computer Engineering Theses & Dissertations

Images captured by wide-angle cameras show barrel type spatial distortion due to wide-angle configuration of the camera lens where image regions farther from the center are compressed in a nonlinear fashion. The barrel distortion correction technique based on least squares estimation attempts to correct a distorted image by expanding it nonlinearly so that straight lines in the object space remain straight in the image space. The intensity value of a pixel in the expanded image is calculated by back mapping its position to the corresponding position in the distorted image and performing linear interpolation on the neighboring pixels. Distorted images …

Analysis Of Ingaassb/Aigaassb Photodetectors For Applications At The 2.0 Micron Wavelengths, Phani Pendyala

Electrical & Computer Engineering Theses & Dissertations

The study of an InGaAsSb-based heterojunction avalanche photo detector has been carried out for 2-μm applications. A separate absorption and multiplication structure was used because it minimizes the tunneling component of the dark current in the absorption region, and also provides single-carrier injection into the multiplication region. This is a well-known requirement for reducing the multiplication noise. The primary goal was to evaluate the potential of InGaAsSb-AlGaAsSb photo-detectors for photodetection at the two-micron wavelength.

InGaAsSb is a relatively new material, and, therefore, characterization and photodetector response analysis based on this material are not available in the literature. In this thesis …

Adaptive Segmentation Techniques For Object Region Extraction From Images With Complex Lighting Environment, Deepthi P. Valaparla

Electrical & Computer Engineering Theses & Dissertations

Automated image segmentation of objects in complex lighting environments is a difficult task since it is not possible to pre-define a threshold to distinguish the object from the background. It is ascertained that an effective threshold citation for such objects depends on the negative binomial distribution of the object region with respect to the background lighting. Based on this concept, a novel adaptive threshold selection method for automatic segmentation of the lumen region in endoscopic images is presented in this thesis. More precise lumen region and boundary are obtained by an integrated neighborhood search based region growing procedure whose speed …

Evaluation Of Distributed Effects In Field Effect Transistors For High Frequency Applications, Srinivas Rowjee Cuddapah

Electrical & Computer Engineering Theses & Dissertations

Metal Semiconductor Field Effect Transistors are at the heart of currently used microwave and millimeter-wave devices. CAD (Computer Aided Design) models for MESFET are used in the development and optimization of high-speed microwave devices. The increase in the chip density demands more accurate models. A distributed small signal model was developed for a GaAs MESFET account of the high frequency effects.

The lumped model of the MESFET is inadequate at frequencies where the wavelength of operation approaches device dimensions. This is because different regions in the device can experience different amplitudes and phases of the biasing signal. In this thesis, …

Yet Another Algorithm For Pitch Tracking (Yaapt), Kavita Kasi

Electrical & Computer Engineering Theses & Dissertations

This thesis presents a pitch detection algorithm that is extremely robust for both high quality and telephone speech. The kernel method for this algorithm is the Normalized Cross Correlation (NCCF) reported by David Talkin [16]. Major innovations include: processing of the original acoustic signal and a nonlinearly processed version of the signal to partially restore very weak F0 components; intelligent peak picking to select multiple F0 candidates and assign merit factors; and, incorporation of highly robust pitch contours obtained from smoothed versions of low frequency portions of spectrograms. Dynamic programming is used to find the ''best" pitch track among all …

Phase-Sensitive Detection Electronics For Wavelength Modulation Spectroscopy Experiments, Tyrone Pate

Electrical & Computer Engineering Theses & Dissertations

Wavelength modulation spectroscopy (WMS) is a non-intrusive detection technique, which enables the measurement of several parameters such as pressure, concentration, and temperature of a species of interest by analyzing the latter's absorption lineshape profile. The method employs a synchronous modulation and detection apparatus to increase the signal to noise ratio and hence the sensitivity of the measurement. Phase-sensitive detection and demodulation of the signal is performed at the modulation frequency and its harmonics. Research at ODU demonstrates that each particular measurement can be performed optimally at an appropriate harmonic of the modulation frequency. The most suitable harmonic depends on many …