Digital Commons Network^™

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 …

Actuator Fault Compensation For A Helicopter Model, Xiao-Hua Yu

Electrical Engineering

A fault-tolerant system is the one that can continue its operation without significant impact on performance in the presence of hardware and/or software errors. In this paper, the design of a fault-tolerant flight controller to control UH-60 helicopter is investigated. A 9th-order state space representation of the helicopter model operating at the forward mode with 80 knots is presented; then a fault-tolerant optimal feedback controller is designed and tested.

Improving Learning Implicit User Interest Hierarchy With Variable Length Phrases, Hyoung-Rae Kim, Philip K. Chan

Electrical Engineering and Computer Science Faculty Publications

A continuum of general to specific interests of a user called a user interest hierarchy (UIH) represents a user's interests at different abstraction levels. A UIH can be learned from a set of web pages visited by a user. In this paper, we focus on improving learning the UIH by adding phrases. We propose the VPF algorithm that can find variable length phrases without any user-defined parameter. To identify meaningful phrases, we examine various correlation functions with respect to well-known properties and other properties that we propose.

Pulse Train™, A Novel Digital Control Method, Applied To A Discontinuous Conduction Mode Flyback Converter, Mark Telefus, Anatoly Shteynberg, Mehdi Ferdowsi, Ali Emadi

Electrical and Computer Engineering Faculty Research & Creative Works

Pulse Train^TM, a new digital control technique for DC-DC converters is introduced and applied to a Flyback converter operating in discontinuous conduction mode (DCM). In contrast to the conventional analog control methods, the principal idea of this new algorithm is to use real time analysis. The proposed technique is appropriate for any converter operating in DCM. However, this work mainly focuses on Flyback converter. In this paper, the main mathematical concept of the new control algorithm is introduced and simulations as well as experimental results are presented.

New Full Wave Theory For Plane Wave Scattering By A Rough Dielectric Surface - The Fictitious Current Method, Byung-Tae Yoon

Dissertations

A new full wave method for scattering of plane waves from a rough dielectric surface is developed. This new theory begins by postulating a zero-order field solution which does not satisfy Maxwell's source-free field equations. The zero-order field, however, is made to satisfy Maxwell's source equations. This is done by introducing a fictitious volume current distribution. Since the original problem does not possess a volume current distribution, its introduction represents a measure of the error in the postulated zero-order solution. To improve this solution, the fictitious volume current distribution is cancelled by the introduction of a second fictitious current distribution, …

Time-Frequency Investigation Of Heart Rate Variability And Cardiovascular System Modeling Of Normal And Chronic Obstructive Pulmonary Disease (Copd) Subjects, Douglas Alan Newandee

Dissertations

A study has been designed to add insight to some questions that have not been fully investigated in the heart rate variability field and the cardiovascular regulation system in normal and Chronic Obstructive Pulmonary Disease (COPD) subjects. It explores the correlations between heart rate variability and cardiovascular regulation, which interact through complex multiple feedback and control loops. This work examines the coupling between heart rate (HR), respiration (RESP), and blood pressure (BP) via closed-loop system identification techniques in order to noninvasively assess the underlying physiology.

In the first part of the study, the applications of five different bilinear time-frequency representations …

Improving The Process Of Laser Retinal Eye Surgery Using Electro Static Micro Mirrors, Narashiman Chakravarthy

Theses

This thesis describes an improved system for laser eye surgery. The system incorporates hardware based image matching and MEMS micromirrors for feedback control of laser positioning on the eye. Many benefits are described in this thesis, such as nulling out eye movement, tracking laser firing history, enabling precise control of laser firing locations and preventing firing accidents. The aim of this work is to frame this improved laser surgery concept and prove the principle of various components of the system. A featured accomplishment is the modeling and simulation of a prototype microcontroller using VHDL that may be incorporated as part …

Characterization And Mapping Of Crystal Defects In Silicon Carbide, Ejiro Emorhokpor

Theses

Silicon carbide (SiC) is a semiconductor with attractive properties, such as a wide bandgap (3. 26 eV), high dielectric strength, and high thermal conductivity that make it suitable for high power, highspeed electronic devices. A major roadblock to its wider application is the presence of defects, particularly micropipes and dislocations, in SiC wafers produced today and decreasing density of these defects is the most important challenge of the industry. The goal of this thesis was to design, build and test a system for detection and analysis of the defects in SiC wafers. The system is based on the reflection optical …

Spatio-Temporal Correlation Models For Indoor Mimo Channels, Kaustubha Raghukumar

Theses

Accurate modeling of the spatio-temporal cross-correlation between the subchannels of a multiple-input multiple-output (MIMO) channel is an important prerequisite of multi-element antenna system design. In this thesis, a new model for indoor MIMO channels is proposed, and a closed form expression for the spatio-temporal cross-correlation function is derived. This new analytical correlation expression includes many physical parameters of interest such as the angle-of-arrivals at the base station and the user, the associated angle spreads, and other parameters, in a compact form. Comparison of this model with narrowband indoor MIMO data collected at Brigham Young University exhibits the utility of the …

Sparse Matrix Product Implementation On Field Programmable Gate Arrays (Epgas), Amit Mahendra Sheth

Theses

If dense matrix multiplication algorithms are used with sparse matrices, they can result in a large number of redundant calculations, as numerous elements in sparse matrices are zero valued, thus available resources and time may be wasted. The algorithm discussed here aims to take advantage of the sparseness of the matrices by multiplying only nonzero elements.

The NIOS development board from Altera is used for implementing the above algorithm. First a sequential program in the C programming language is downloaded onto the FPGA and run by the NIOS soft-processor. Then the same board is also used for a parallel implementation …

Oxidation Behavior Of Zr-Cu-Al-Ni Amorphous Alloys In Air At 300～500℃, H. H. Hsieh, W. Kai, T. G. Neih, Y. Kawamura

Journal of Electrochemistry

The oxidation behavior of the Zr- based bulk amorphous alloy (BMG; Zr-30Cu-10Al-5Ni in at.%) was studied in dry air over the temperature range 300～500 ℃. The kinetic results indicated that the amorphous alloy oxidized linearly at 300 ℃, while the parabolic oxidation was observed at 350～425 ℃, and the oxidation behavior at 500 ℃ was irregular and complicated. In general, the scales formed on the surface of the amorphous alloy were temperature-dependent, consisting of tetragonal-ZrO₂ at 300 ℃, and of mostly tetragonal-ZrO₂ as well as minor amounts of monoclinic-ZrO₂ and CuO at T ≥ 350 ℃.

Synthesis And Electrochemical Characteristics Of Nickel-Based Complex Oxide LiANi0.78Co0.2Cd0.02O2, Rong-Zhong Yuan, Mei-Zhen Qu, Zuo-Long Yu

Journal of Electrochemistry

The nickel-based complex oxide Li_aNi_0.78Co_0.02O₂ cathode materials for lithium-ion rechargeable batteries was synthesized by the improved solid-state reaction method with LiOH·H₂O, ball-like Cd-doped Ni(OH)₂ and Co₂O₃ as raw materials. The analysis ICP-AES proved that the as-prepared compounds were near the stoichiometric form. The XRD, SEM and electrochemical characteristics testing were also carried out. The results showed that the complex cathode material Li_aNi_0.78Co_0.2Cd_0.02O₂ has layered structure, homogeneous surface distributions,uniform particles with good crystal morphology as well as stable electrochemical …

Perfluorinated Sulfonic Acid Lithium Conductivity Humidity Sensor, Hong-Feng Xu, Jing Liu, Li Wan

Journal of Electrochemistry

Treat carbon paper with 3% PTFE solution and dried in 340 ℃ for 40 minutes to enhance its intension, and level off the surface of the carbon paper with a mixture of XC-72 carbon black and PTFE solution. With those treated carbon paper as electrodes, recast Nafion thin film from 5% Nafion solution as humidity sensitive material, a solid polymer electrolyte humidity sensor was prepared on a thin PET film. Take the relative humidity data from several saturated salt solutions, the relationship between conductivity response and relative humidity was studied at different relative humidies .The results showed: when the polymer …

Conductance Properties For Electrolyte Of Lithium Ion Battery At Low Temperature, Jing-Li Han, Yan-Mei Yu, Jian Chen, Chun-Tong Wang

Journal of Electrochemistry

The system of LiPF₆-ethylene carbonate (EC)-methy1 acetate (MA) was studied. The conductivities of this system were measured under various composition and various salt concentrations at temperature range of 20～-50 ℃. The optimum composition of this system was selected. The tests of cyclic voltammography and charge-discharge were carried out. This system was compared with commercial electrolyte solution.

Electrochemical Monitoring On The Deactivation Of A Metallic Oxide Anode, Li-Kun Xu, Shi-Zhe Song, Ting-Yong Wang, Guang-Zhang Chen

Journal of Electrochemistry

The process of accelerated life test of an IrO₂/Ta₂O₅ coated titanium anode was monitored using cyclic voltammetry and electrochemical impedance spectroscopy. The vatiation with electrolysis time of anodic voltammetric charge Q^*, the double layer capacitance C_dl,the oxide film resistance R_f and the charge transfer resistance R_ct for oxygen evolution was measured. A deactivation mechanism was proposed based on the observation results.

Corrosion Prediction Of Carbon Steel In Concentrated Lithium Bromide Solutions At High Temperature Using Bp Neural Network, Nai-Bao Huang, Cheng-Hao Liang

Journal of Electrochemistry

Neutral network model has been developed for the computation of corrosion rate of carbon steel in LiBr solutions.The results indicate that the model is capable of reproducing the effects of changes in alkalinity, temperatures, LiBr and Na₂MoO₄ concentrations on the rates of general corrsion and good agreement between calculated and experimental corrosion rate is obtained. The model can be used to satisfactorily predict the corrosion rate of carbon steel in different concentrations of LiBr solutions containing different inhibitors at different temperatures. It also provides a novel method for corrosion monitoring of metals used in LiBr absorption chiller.

Yscat Backscatter Distributions, Benjamin E. Barrowes

Theses and Dissertations

YSCAT is a unique ultrawideband microwave scatterometer developed to investigate the sea surface under a variety of environmental and radar parameters. The YSCAT94 experiment consisted of a six month deployment on the WAVES research tower operated by the Canada Center for inland Waters (CCIW). Over 3500 hours of data were collected at 2Γ 3.05Γ 5.3Γ 10.02Γ and 14 GHz and at a variety of wind speeds, relative azimuth angles, and incidence angle.

A low wind speed "rolloff" of the normalized radar cross section (σ°) in YSCAT94 data is found and quantified. The rolloff wind speedΓ γΓ is estimated through regression …

Uncertainties In Oceanic Microwave Remote Sensing: The Radar Footprint, The Wind-Backscatter Relationship, And The Measurement Probability Density Function, Paul E. Johnson

Theses and Dissertations

Oceanic microwave remote sensing provides the data necessary for the estimation of significant geophysical parameters such as the near-surface vector wind. To obtain accurate estimates, a precise understanding of the measurements is critical. This work clarifies and quantifies specific uncertainties in the scattered power measured by an active radar instrument.

While there are many sources of uncertainty in remote sensing measurements, this work concentrates on three significant, yet largely unstudied effects. With a theoretical derivation of the backscatter from an ocean-like surface, results from this dissertation demonstrate that the backscatter decays with surface roughness with two distinct modes of behavior, …

Evolutionary Algorithms For Beginners, Marek Perkowski

Electrical and Computer Engineering Faculty Publications and Presentations

This presentation offers a detailed introduction into the concepts and applications of evolutionary ideas in computing, adapted from genetics and evolution.

Optimal Beam Splitters For The Division-Of-Amplitude Photopolarimeter, R. M.A. Azzam, A. De

Electrical Engineering Faculty Publications

Optimal optical parameters of the beam splitter that is used in the division-of-amplitude photopolarimeter are determined. These are (1) 50%–50% split ratio of the all-dielectric beam splitter, (2) differential phase shifts in reflection and transmission Δ_r and Δ_t that differ by ±π/2, and (3) ellipsometric parameters (ψ_r, ψ_t)= (27.368°, 62.632°) or (62.632°, 27.368°). It is also shown that for any nonabsorbing beam splitter that splits incident unpolarized light equally, the relationship ψ_r+ψ_t=π/2 is always satisfied.

Spatial And Temporal Considerations In Vehicle Path Tracking With An Emphasis On Spatial Robustness, Donald L. Cripps

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This dissertation researches the task and path management of an autonomous vehicle with Ackerman-type steering.

The task management problem was approached as a path training operation in which a human operator drives the desired path through an environment. A training trajectory is converted into a series of path segments that are driveable by the autonomous vehicle by first fitting a general path to the dataset. Next, transition segments are added to the general path to match the vehicle velocity and steering angle rate limit.

The path management problem has been approached by first deriving a kine- matic model of the …

Cellular Automata Realization Of Regular Logic, Andrzej Buller, Marek Perkowski

Electrical and Computer Engineering Faculty Publications and Presentations

This paper presents a cellular-automatic model of a reversible regular structure called Davio lattice. Regular circuits are investigated because of the requirement of future (nano-) technologies where long wires should be avoided. Reversibility is a valuable feature because it means much lower energy dissipation. A circuit is reversible if the number of its inputs equals the number of its outputs and there is a one-to-one mapping between spaces of input vectors and output vectors. It is believed that one day regular reversible structures will be implemented as nanoscale 3-dimensional chips. This paper introduces the notion of the Toffoli gate and …

Foreword Advanced Emc Numerical Modeling, Christos Christopoulos, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

No abstract provided.

Assessing Classification Confidence Using A Weighted Exponential Based Technique With The Learn++ Incremental Learning Algorithm, Jeffrey T. Byorick

Theses and Dissertations

Pattern recognition problems span a broad range of applications, where each application has its own tolerance on classification error. The varying levels of risk associated with many pattern recognition applications indicate the need for a versatile algorithm with the ability to measure its own reliability. In this work, the supervised incremental learning algorithm Learn++ [1, 2], which exploits the synergistic power of an ensemble of classifiers, is further developed to add the capability of assessing its own confidence. Estimation of the true generalization performance of the classifier as well as the confidences on classification of individual data instances is investigated …

Wide Angle Achromatic Prism Beam Steering For Infrared Countermeasures Applications, Bradley D. Duncan, Philip J. Bos, Vassili Sergan

Electro-Optics and Photonics Faculty Publications

The design and analysis of achromatic doublet prisms for use in laser beam steering is presented. The geometric relationships describing the maximum steering angle are given, as are discussions of first- and second-order dispersion reduction. Infrared (IR) material alternatives and optimum IR material characteristics for wide-angle achromatic prism beam steering are also investigated. Sixteen materials in 120 different combinations have been examined to date. For midwave IR applications it is shown that the minimum dispersion currently achievable across the full 2 to 5 μm spectrum is 1.7816 mrad at an average maximum steering angle of 45 deg. This is accomplished …

Complex Low-Pass Filters, Peter Kiss, Vladimir I. Prodanov, Jack Glas

Electrical Engineering

Zero-if transceivers suffer from the imbalance of the I and Q paths. By using a complex low-pass filter topology instead of a conventional pair of real low-pass filters, this imperfection can be reduced. Both analytical and numerical analysis show that the proposed technique is significantly more robust to circuit imperfections than the traditional architecture.

Understanding Wavelet Analysis And Filters For Engineering Applications, Chethan Bangalore Parameswariah

Doctoral Dissertations

Wavelets are signal-processing tools that have been of interest due to their characteristics and properties. Clear understanding of wavelets and their properties are a key to successful applications. Many theoretical and application-oriented papers have been written. Yet the choice of a right wavelet for a given application is an ongoing quest that has not been satisfactorily answered. This research has successfully identified certain issues, and an effort has been made to provide an understanding of wavelets by studying the wavelet filters in terms of their pole-zero and magnitude-phase characteristics. The magnitude characteristics of these filters have flat responses in both …

A Representation Scheme For Finite Length Strings, Guarav Tandon, Debasis Mitra

Electrical Engineering and Computer Science Faculty Publications

This study is an attempt to create a canonical representation scheme for finite length strings to simplify the study of the theory behind different classes of patterns and to ease the understanding of the underlying separability issues. This could then be used to determine what kinds of techniques are suitable for what class of separability (linear, multi-linear, or non-linear). This representation can then be used in intrusion detection, biological sequences, pattern recognition/classification and numerous other applications.

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 …

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 …