Engineering Commons^™

Two Methods Of Neural Network Controlled Dynamic Channel Allocation For Mobile Radio Systems, Kelvin T. Erickson, Edward J. Wilmes

Electrical and Computer Engineering Faculty Research & Creative Works

Two methods of dynamic channel allocation using neural networks are investigated. Both methods continuously optimize the mobile network based on changes in calling traffic. The first method uses backpropagation model predictions to aid the channel allocator. Each cell contains a backpropagation model which provides the channel allocator a call traffic prediction allowing the channel allocator to effectively optimize the network. The second method uses the same backpropagation models along with actor-critic models to perform the channel allocation. The actor-critics learn to model traffic activity between adjacent cells in real-time, and thereby learn to allocate channels dynamically between cells. The learning …

Evaluating The Value Of Distributed Photovoltaic Generations In Radial Distribution Systems, Badrul H. Chowdhury, A. W. Sawab

Electrical and Computer Engineering Faculty Research & Creative Works

The impact of photovoltaic (PV) generations, when added to an existing rural utility's distribution system, is studied. The addition of PV is examined in the light of voltage support, loss reduction, and reduction in peak demand. Comparisons are made with the conventional and widely used methods for voltage control and loss minimization, such as the addition of series and shunt capacitors and voltage regulators. The economics of distributed PV systems in the context of conventional grid power purchases are also studied. Results of this study are meant to be used as general guidelines for evaluating the impact of significant PV …

An Experimentally Obtainable Heat Source Due To Absorption Of Ultrasound In Biological Media, James L. Drewniak, F. Dunn

Electrical and Computer Engineering Faculty Research & Creative Works

Deposition of heat as a result of loss in an ultrasonic wave may result in damage to biological tissues. The extensive use of ultrasound for diagnostic purposes during pregnancy necessitates the evaluation of thermal risk to a developing fetus during routine clinical exposures. Because of the small ultrasonic absorption coefficient in soft tissues at low megahertz frequencies, temperature elevations exceeding 1 °C are not expected from clinically employed ultrasound systems, and there is no evidence that such small temperature increases can result in deleterious effects. However, when the propagation path includes bone, which is known to be highly lossy, theoretical …

Input Dimension Reduction In Neural Network Training-Case Study In Transient Stability Assessment Of Large Systems, S. Muknahallipatna, Badrul H. Chowdhury

Electrical and Computer Engineering Faculty Research & Creative Works

The problem in modeling large systems by artificial neural networks (ANN) is that the size of the input vector can become excessively large. This condition can potentially increase the likelihood of convergence problems for the training algorithm adopted. Besides, the memory requirement and the processing time also increase. This paper addresses the issue of ANN input dimension reduction. Two different methods are discussed and compared for efficiency and accuracy when applied to transient stability assessment.

Jitter And Wander Reduction For A Sonet Ds3 Desynchronizer Using Predictive Fuzzy Control, Kevin Blythe Stanton

Dissertations and Theses

Excessive high-frequency jitter or low-frequency wander can create problems within synchronous transmission systems and must be kept within limits to ensure reliable network operation. The emerging Synchronous Optical NETwork (SONET) introduces additional challenges for jitter and wander attenuation equipment (called desynchronizers) when used to carry payloads from the existing Plesiochronous Digital Hierarchy (PDH), such as the DS3. The difficulty is primarily due to the large phase transients resulting from the pointer-based justification technique employed by SONET (called Pointer Justification Events or PJEs). While some previous desynchronization techniques consider the buffer level in their control actions, none has explicitly considered wander …

Surface Debye Temperature Measurement With Reflection High-Energy Electron Diffraction, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Measurement of the surface mean-square atomic vibrational amplitude, or equivalently the surface Debye temperature, with reflection high-energy electron diffraction is discussed. Low-index surfaces of lead are used as examples. Particular details are given about the temperature-dependent diffraction pattern of Pb(100) in the Debye-Waller region. The use of reflection high-energy electron diffraction for measurement of the substrate surface temperature in thin-film deposition chambers is suggested. © 1996 American Institute of Physics.

Improved Methods For Electroplating Cadmium Sulfide Thin Films, Brandon Kemp, Robert Engelken, Arif Raza, Wasim Aleem, Imran Khan, Chris Barber

Journal of the Arkansas Academy of Science

We report improved methods for electroplating cadmium sulfide (CMS) films. Aprevious problem was cracking/flaking of films deposited from organic solutions of elemental sulfur; attempts to improve adhesion via bath additives reduced grain size. Aqueous baths of thiosulfate ions yield cadmium-richness at low T temperatures (T), long deposition times, and/or poor bath stability. Developments in our work to be discussed include (1) plating ofuniform, adherent, and stoichiometric CdS from tetraethylene baths of CdCl 2 and elemental sulfur at T >70° C with minimal cracking/flaking, (2) improved uniformity/ adherence by use of CdL>, and (3) swept voltage methods in aqueous thiosulfate …

An Investigation Into Manufacturing Execution Systems, K. W. Duley

Theses : Honours

Hardware and software developments of this decade have exposed an hiatus between business/management applications and process control in heavy industry in the implementation of computer technology. This document examines the development of discrete manufacturing and of relevant implementations of computing. It seeks to examine and to clarify the issues involved in a perceived current drive to bridge this gap, to integrate all the systems in a manufacturing enterprise in a Manufacturing Execution System (MES) in order to address two hypotheses: I) That overseas trends towards the development of manufacturing execution systems have application in the Australian industrial context. 2) That …

Analysis Of Frequency Selective Surfaces With Ferrite Substrates, Youcheng Liu

Retrospective Theses and Dissertations

Frequency selective surfaces (FSS) have numerous applications in several microwave and optical systems. Most frequency selective surface structures have one or more dielectric substrates. In this work, instead of traditional dielectric substrates, ferrite substrates are used under different dc bias conditions. By using ferrite materials, one can change the spectral properties of these structures without physically altering them. An applied magnetic field (dc bias) on the ferrite substrate changes its properties and hence the electrical dimensions of the elements comprising the periodic structure. Thus by simply applying a dc bias, the transmission and reflection properties of the periodic structure can …

Interaction Between Millimeter Oscillations And Monocrystal Hexagonal Ferrites With Modulated Resonance Frequency, Alexander A. Kitaytsev, Marina Koledintseva

Electrical and Computer Engineering Faculty Research & Creative Works

Investigation of non-linear stable effects taking place at ferromagnetic resonance (FMR) in monocrystal arbitrarily oriented hexagonal ferrite resonators (HFR) with controlled (modulated) resonance frequency is an urgent problem. The presented analysis is based on two approaches: the “quasistatic” approach using the static tensor of the HFR magnetic susceptibility and the “dynamic” one based on the solution of the magnetization vector motion equation (MVME) with varying time coefficients due to modulated magnetization field or HFR angle of orientation. The first approach is valid at low modulation frequencies (in comparison with the relaxation frequency of the HFR) and the second one can …

Security-Constrained Optimal Rescheduling Of Real Power Using Hopfield Neural Network, S. Ghosh, Badrul H. Chowdhury

Electrical and Computer Engineering Faculty Research & Creative Works

A new method for security-constrained corrective rescheduling of real power using the Hopfield neural network is presented. The proposed method is based on solution of a set of differential equations obtained from transformation of an energy function. Results from this work are compared with the results from a method based on dual linear programming formulation of the optimal corrective rescheduling. The minimum deviations in real power generations and loads at buses are combined to form the objective function for optimization. Inclusion of inequality constraints on active line flow limits and equality constraint on real power generation load balance assures a …

A Hybrid Observer For High Performance Brushless Dc Motor Drives, Keith Corzine, S. D. Sudhoff

Electrical and Computer Engineering Faculty Research & Creative Works

Brushless DC motor drive systems are used in a wide variety of applications. These drives may be classified as being one of two types: sinusoidal drives in which there are no low-frequency harmonics in the current waveforms and no low-frequency torque ripple; and nonsinusoidal drives in which there is considerable low-frequency harmonic content, both in the current and torque waveforms. Although sinusoidal drives feature superior performance, they are generally more expensive since rotor position must be sensed on a continuous basis, thus requiring an optical encoder or a resolver, whereas relatively inexpensive Hall-effect sensors may be used for nonsinusoidal drives. …

Extended Kalman Filter For Photographic Data From Impact Acceleration Tests, Edit J. Kaminsky, R. E. Trahan, P. M. Chirlian, B. King

Electrical Engineering Faculty Publications

This paper presents the development of an Extended Kalman Filter (EKF) that optimally processes photographic data collected during short-duration impact acceleration tests. The system is modeled by a non-linear state-space representation using quaternions for rotational kinematics. Three cameras are used to photograph up to 14 fiducials mounted on a plate attached to the subject's mouth. The filter yields the history of the rotational and translational kinematics of the origin of the mouth plate. Results from the EKF and analysis of the estimation error are presented.

A Self-Consistent Numerical Method For Simulation Of Quantum Transport In High Electron Mobility Transistor; Part 1: The Boltzmann-Poisson-Schrodinger Solver, Rahim Khoie

Electrical & Computer Engineering Faculty Research

A self-consistent Boltzmann-Poisson-Schrödinger solver for High Electron Mobility Transistor is presented. The quantization of electrons in the quantum well normal to the heterojunction is taken into account by solving the two higher moments of Boltzmann equation along with the Schrödinger and Poisson equations, self-consistently. The Boltzmann transport equation in the form of a current continuity equation and an energy balance equation are solved to obtain the transient and steady-state transport behavior. The numerical instability problems associated with the simulator are presented, and the criteria for smooth convergence of the solutions are discussed. The current-voltage characteristics, transconductance, gate capacitance, and unity-gain …

A Self-Consistent Numerical Method For Simulation Of Quantum Transport In High Electron Mobility Transistor; Part Ii: The Full Quantum Transport, Rahim Khoie

Electrical & Computer Engineering Faculty Research

In Part I of this paper we reported a self-consistent Boltzmann-Schrodinger-Poisson simulator for HEMT in which only electrons in the first subband were assumed to be quantized with their motion restricted to 2 dimensions. In that model, the electrons in the second and higher subbands were treated as bulk system behaving as a 3 dimensional electron gas. In Part II of this paper, we extend our simulator to a self-consistent full-quantum model in which the electrons in the second subband are also treated as quantized 2 dimensional gas. In this model, we consider the electrons in the lowest two subbands …

Generalized Beam Matrices. Ii. Mode Selection In Lasers And Periodic Misaligned Complex Optical Systems, Lee W. Casperson, Anthony A. Tovar

Electrical and Computer Engineering Faculty Publications and Presentations

A generalized beam matrix method is used to investigate the mode structure of astigmatic misaligned optical systems with loss or gain. In these optical systems the usual real-argument polynomial-Gaussian beams are not eigenfunctions, and off-axis complex-argument polynomial beams must be used. New beam transformations for these complex-argument modes are reported. Stability criteria are developed, and mode selection in laser resonators that contain tilted, displaced, or curved complex optical elements is discussed.

Fault Classification Using Kohonen Feature Mapping, Badrul H. Chowdhury, Kunyu Wang

Electrical and Computer Engineering Faculty Research & Creative Works

Applications of neural networks to power system fault diagnosis have provided positive results and shown advantages in process speed over conventional approaches. This paper describes the application of a Kohonen neural network to fault detection and classification using the fundamental components of currents and voltages. The Electromagnetic Transients Program is used to obtain fault patterns for the training and testing of neural networks. Accurate classifications are obtained for all types of possible short circuit faults on test systems representing high voltage transmission lines. Short training time makes the Kohonen network suitable for on-line power system fault diagnosis. The method introduced …

Application Of Autoregressive Moving Average Linear Prediction Filters To The Characterization Of Solar Wind-Magnetosphere Coupling, Carter N. Borst

Theses and Dissertations

Linear prediction filtering techniques have been used in studying the coupling processes between the solar wind and magnetosphere. The magnetosphere is a complex, dynamic system with at least two independent coupling methods for energy input, driven and unloading. Linear models were built and tested on the Bargatze data set, consisting of over 70 days of geomagnetic indices and solar wind data ordered in 34 intervals of increasing geomagnetic activity. Linear filtering techniques employing single-and multiple-input, autoregressive models predicted values of the magnetic index AL from solar wind data. The impulse response curves of the AL-coupling function groups showed amplitude peaks …

Discrete Riccati Equation Solutions: Distributed Algorithms, Demetrios G. Lainiotis, Konstantinos N. Kostas Plataniotis, Paraskevas Papaparaskeva

Electrical Engineering and Computer Science Faculty Publications

In this paper new distributed algorithms for the solution of the discrete Riccati equation are introduced. The algorithms are used to provide robust and computational efficient solutions to the discrete Riccati equation. The proposed distributed algorithms are theoretically interesting and computationally attractive.

Modelling An Optical Fiber Bragg Grating, Claudio Oliveira Egalon

Electrical & Computer Engineering Theses & Dissertations

A theoretical investigation of a single mode optical fiber with one and two superimposed Bragg grating is presented. The formulation relies in the determination of an approximate solution in the asymptotic region of one of the fiber parameters. A correction is then applied to the asymptotic solution using the Method of the Successive Approximations also known as the Piccard Method. The approximation was then compared to the numerical solution using the Runge-Kutta method. Assuming that each Bragg grating has modulation frequencies given by Ω₁ and Ω₂, it has been found that the second Bragg grating shifts the …

Optical Fiber Fourier Transform Infrared Evanescent Wave Absorption Spectroscopy Of Aluminum Hydroxide And Natural Corrosion, Juock S. Namkung

Electrical & Computer Engineering Theses & Dissertations

A new technique for continuous, real-time, in-situ detection of natural corrosion of aluminum alloys is presented. The technique is a generalized version of attenuated total reflectance (ATR) spectroscopy, that combines optical fibers and a Michelson interferometer spectrometer to make evanescent wave absorption measurements. Aluminum hydroxide is one of the major corrosion products of aluminum. Absorption spectra of powdered samples of aluminum corrosion, in the spectral region around three micrometers have been studied and compared with the spectra from pure powdered aluminum hydroxide. A chalcogenide optical fiber was used as an attenuated total reflectance (ATR) optical element. The same samples were …

A Simulation Environment For Cdma Wireless Communication Systems In Awgn Channels, Muzaffer Kanaan

Theses

The goal of this work is the development of a, wireless communication system simulator. The simulator has been developed primarily to aid in the studies of Code Division Multiple Access (CDMA) digital cellular systems. We begin by introducing the fundamentals of spread spectrum communications and the motivation for this work. We then take a detailed look at CDMA systems and their structure. We then verify the accuracy of the simulator by using it to simulate some familiar system scenarios. We end this work by presenting conclusions and suggestions for further work.

Asynchronous Multiuser Decorrelating Detector For Awgn Channel, Ashwini A. Borkar

Theses

Decorrelating detector is one of the sub-optimum detectors for CDMA applications that generally has better performance than the conventional detector and is near-far resistant. Synchronous decorrelating detector employing DPSK modulation is considered and its simulation results are presented.

Attention is focussed on one-shot decorrelating detector for a two user case for asynchronous transmission, where each symbol interval is considered seperately. Initially the performance of the detector with exact estimation of the relative delay is analyzed and then the effect of inaccurate estimation on the probability of error is discussed.

Flash Adc Using 2Μm Cmos P-Well Technology : Design And Test, Joseph E. Levinson

Theses

This thesis describes the design, implementation and test for a new CMOS analog-to-digital converter IC chip. In designing the analog-to-digital converter in this thesis a radically different comparator design that is only available with CMOS logic. The design utilizes a single CMOS inverter as an ultra-high gain amplifier. This approach reduces the circuit dependence upon matching of the transistors similar to the traditional method. This new design requires less area since the comparator utilizes fewer transistors.

Flash analog-to-digital converters use 2" - 1 comparators to do a single conversion where n is the number of bits used. These comparators are …

Surface-Related Breakdown In Silicon: Imaging Of Current Filaments In Long P+-N--N+ Structures, B. J. Hankla, P. F. Williams, G. A. Frecks, F. E. Peterkin

P. F. (Paul Frazer) Williams Publications

We present Schlieren images which show the existence and evolution of current filaments during the very early stages of surface-related breakdown inside 1 cm silicon p⁺-n^--n⁺ structures. These images confirm our previous finding that breakdown occurs in the silicon rather than in the ambient, and suggest that a streamerlike mechanism may be responsible.

Minimization Of Sum-Of-Conditional-Decoders Structures With Applications In Finite Machine Epld Design And Machine Learning, Sanof Mohamedsadakathulla

Dissertations and Theses

In order to achieve superior speed in sequencer designs over competing PLD devices, Cypress brought to market an innovative architecture, CY7C361. This architecture introduced a new kind of universal logic gate, the CONDITION DECODER (CDEC). Because there are only 32 macrocells in the chip, saving only one CDEC gate can be quite important (the well-known "fit/no-fit problem"). A problem that is related to the fitting problem of the Cypress CY7C361 chip is the SOC Minimization. Due to the limited low number of macrocells in CY7C361, a high quality logic minimization to reduce the number of macrocells is very important. The …

Maximum Likelihood Estimation Of Wave Front Slopes Using A Hartmann-Type Sensor, Scott A. Sallberg

Theses and Dissertations

Current methods for estimating the wave front slope at the pupil of a telescope equipped with a Hartmann-type wave front sensor (H-WFS) are based on a simple centroid calculation of the intensity distributions (spots) recorded in each subaperture of the H-WFS. The centroid method does not include any knowledge concerning correlation properties of the slopes over the subapertures or the amount of light collected by the telescope and diverted to the H-WFS for wave front reconstruction purposes. This thesis devises a maximum likelihood (ML) estimation of the spot centroids by incorporating statistical knowledge of the spot shifts. The light level …

Improving The Morse Intercept Operator's Audio Display, Jesse M. Washburn

Theses and Dissertations

This thesis improves the audio display for multiple Morse communications. Factors considered to improve the audio display are frequency of source, volume level of source, and methods of unmasking. The best frequency and volume level of a Morse source is 500 Hz at 70 dB sound pressure level (spi). Two types of masking are researched: frequency masking and expectation driven masking. Experiments showed by amplifying high pitched sources the effects of frequency masking are minimized. Other methods to compensate for frequency masking are 3-D sound and the placement of a source out of phase between the ears. Morse code recognition …

The Effect Of Excitation Limits On Voltage Stability, Jyothi Ayyagari, Mariesa Crow

Electrical and Computer Engineering Faculty Research & Creative Works

Voltage collapse has been commonly associated with insufficient reactive power support. Steady state studies have related reactive power generation limitations to the sudden onset of voltage instability. This paper extends this approach to the dynamic case. The relationship between the dynamic models and steady state behavior is established. The dynamic model is then used to investigate the sudden change in system stability when the maximum excitation limit is reached. Several illustrative examples are analyzed. Corrective actions are proposed which will move the physical system away from the region of instability.

Transients In Power Systems, M. Belkhayat, J. Edwards, N. Hoonchareon, O. Marte, D. Stenberg, E. Walters

Department of Electrical and Computer Engineering Technical Reports

Power system engineering largely focuses on steady state analysis. The main areas of power system engineering are power flow studies and fault studies - both steady state technologies. But the world is largely transient, and power systems are always subject to time varying and short lived signals. This technical report concerns several important topics in transient analyses of power systems. The leading chapter deals with a new analytical tool-wavelets-for power system transients. Flicker and electric are furnace transients are discussed in Chapters I1 and IV. Chapter 111 deals with transients from shunt capacitor switching. The concluding chapters deal with transformer …