Computer Engineering Commons^™

Stability Analysis Of A Closed-Loop Control For A Pulse Width Modulated Dc Motor Drive, Fatma Gürbüz, Eyüp Akpinar

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper, the effect of the variation of amplitude and the chopping period of a PWM signal on the stability of a closed-loop control for a DC motor drive is investigated. First, the entire system is formulated as a Linear Quadratic (LQ) tracker with output feedback [1]. Then, stability analysis for the varying amplitude and the varying chopping period is carried out by the methods of root locus and the Jury test. Finally, stability limits obtained from a root locus and Jury test are checked by the simulation of the system in MATLAB.

Plane Wave Diffraction By A Dielectric Loaded Open Parallel Thick Plate Waveguide, Bahatti̇n Türetken, Ali̇ Alkumru

Turkish Journal of Electrical Engineering and Computer Sciences

A uniform asymptotic high-frequency solution for a two-dimensional diffraction problem of plane electromagnetic waves by a dielectric loaded open parallel thick plate waveguide is investigated rigorously using the Fourier transform technique in conjunction with the mode matching method. This mixed method of formulation gives rise to scalar modified Wiener-Hopf equations of the second kind for which the solution contains a set of infinitely many constants satisfying an infinite system of linear algebraic equations. A numerical solution of this system is obtained for various values of plate thickness, incidence angle and permittivity, and the effect of these parameters on the diffraction …

Array Pattern Nulling By Phase And Position Perturbations With The Use Of A Modified Tabu Search Algorithm, Ali̇ Akdağli, Keri̇m Güney

Turkish Journal of Electrical Engineering and Computer Sciences

A useful and flexible method based on the tabu search algorithm for the pattern synthesis of linear antenna arrays with the prescribed nulls is presented. Nulling of the pattern is achieved by controlling both the phase and the position of each array element. To show the versatility of the present method, some design specifications such as the maximum sidelobe level and the null depth level are considered by introducing a set of weighting factors in the cost function constructed for the tabu search algorithm. Several illustrative examples of a Chebyshev pattern with the imposed single, multiple and broad nulls are …

Active Clamped Zvs Forward Converter With Soft-Switched Synchronous Rectifier, A. Açik, Işik Çadirci

Turkish Journal of Electrical Engineering and Computer Sciences

This paper presents the analysis, design and implementation of an active-clamped, ZVS forward converter equipped with a soft-switched synchronous rectifier (ACFC-SR) proposed for high-efficiency, low output voltage dc-dc converter applications. The converter efficiency is maximized due to the soft-switching of the main, active clamp, synchronous rectifier and freewheeling MOSFET switches. The operating principles of the ACFC-SR are analyzed in detail and the converter performance is compared with the alternative forward converter schemes employed in low output voltage dc-dc converters. Experimental results are presented for a converter with a dc input voltage of 48 V, an output voltage of 5 V, …

Boundary Effects On Multiplication Noise In Thin Heterostructure Avalanche Photodiodes: Theory And Experiment [Al/Sub 0.6/Ga/Sub 0.4/As/Gaas], Majeed M. Hayat, Oh-Hyun Kwon, Shuling Wang, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

The history-dependent recurrence theory for multiplication noise in avalanche photodiodes (APDs), developed by Hayat et al., is generalized to include inter-layer boundary effects in heterostructure APDs with multilayer multiplication regions. These boundary effects include the initial energy of injected carriers as well as bandgap-transition effects within a multilayer multiplication region. It is shown that the excess noise factor can be significantly reduced if the avalanche process is initiated with an energetic carrier, in which case the initial energy serves to reduce the initial dead space associated with the injected carrier. An excess noise factor reduction up to 40% below the …

Maximum-Likelihood Image Estimation Using Photon-Correlated Beams, Majeed M. Hayat, Muhammad Sajjad Abdullah, Adel Joobeur, Bahaa E.A. Saleh

Electrical and Computer Engineering Faculty Research and Publications

A theory is presented addressing the fundamental limits of image estimation in a setup that uses two photon-correlated beams. These beams have the property that their photon arrivals, as a point process, are ideally synchronized in time and space. The true image represents the spatial distribution of the optical transmittance (or reflectance) of an object. In this setup, one beam is used to probe the image while the other is used as a reference providing additional information on the actual number of photons impinging on the object. This additional information is exploited to reduce the effect of quantum noise associated …

Gain-Bandwidth Characteristics Of Thin Avalanche Photodiodes, Majeed M. Hayat, Oh-Hyun Kwon, Yi Pan, Paul P. Sotirelis, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

The frequency-response characteristics of avalanche photodiodes (APDs) with thin multiplication layers are investigated by means of a recurrence technique that incorporates the history dependence of ionization coefficients. In addition, to characterize the autocorrelation function of the impulse response, new recurrence equations are derived and solved using a parallel computer. The mean frequency response and the gain-bandwidth product are computed and a simple model for the dependence of the gain-bandwidth product on the multiplication-layer width is set forth for GaAs, InP, Al/sub 0.2/Ga/sub 0.8/As, and In/sub 0.52/Al/sub 0.48/As APDs. It is shown that the dead-space effect leads to a reduction (up …

An Algebraic Algorithm For Nonuniformity Correction In Focal-Plane Arrays, Bradley M. Ratliff, Majeed M. Hayat, Russell C. Hardie

Electrical and Computer Engineering Faculty Research and Publications

A scene-based algorithm is developed to compensate for bias nonuniformity in focal-plane arrays. Nonuniformity can be extremely problematic, especially for mid- to far-infrared imaging systems. The technique is based on use of estimates of interframe subpixel shifts in an image sequence, in conjunction with a linear-interpolation model for the motion, to extract information on the bias nonuniformity algebraically. The performance of the proposed algorithm is analyzed by using real infrared and simulated data. One advantage of this technique is its simplicity; it requires relatively few frames to generate an effective correction matrix, thereby permitting the execution of frequent on-the-fly nonuniformity …

Projection-Based Image Registration In The Presence Of Fixed-Pattern Noise, Ernest Armstrong, Stephen C. Cain, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

A computationally efficient method for image registration is investigated that can achieve an improved performance over the traditional two-dimensional (2-D) cross-correlation-based techniques in the presence of both fixed-pattern and temporal noise. The method relies on transforming each image in the sequence of frames into two vector projections formed by accumulating pixel values along the rows and columns of the image. The vector projections corresponding to successive frames are in turn used to estimate the individual horizontal and vertical components of the shift by means of a one-dimensional (1-D) cross-correlation-based estimator. While gradient-based shift estimation techniques are computationally efficient, they often …

Statistical Evaluation Of Image Quality Measures, Ismail Avcibas, Bulent Sankur, Khalid Sayood

Department of Electrical and Computer Engineering: Faculty Publications

In this work we comprehensively categorize image quality measures, extend measures defined for gray scale images to their multispectral case, and propose novel image quality measures. They are categorized into pixel difference-based, correlation-based, edge-based, spectral-based, context-based and human visual system (HVS)-based measures. Furthermore we compare these measures statistically for still image compression applications. The statistical behavior of the measures and their sensitivity to coding artifacts are investigated via analysis of variance techniques. Their similarities or differences are illustrated by plotting their Kohonen maps. Measures that give consistent scores across an image class and that are sensitive to coding artifacts are …

Feedback Correction Of Angular Error In Grating Readout, Monish Ranjan Chatterjee, Sundaram Ramachandran

Electrical and Computer Engineering Faculty Publications

Angular and wavelength READ beam errors in holographic interconnection systems are often a recurrent problem. Several strategies have been proposed to minimize or eliminate such READOUT misalignments.

Some years ago, Chatterjee and co-workers proposed a method involving READ beam wavelength tuning to correct output angular errors. In this paper, we investigate the possibility of using an acousto-optic (A-O) Bragg cell with optoelectronic feedback to dynamically correct the scattered beam for deviations in the incidence direction of the READ beam of a hologram. The concept here is based on an acoustic frequency feedback strategy used recently by Balakshy and Kazaryan for …

Characterizing And Calibrating A Large Helmholtz Coil At Low Ac Magnetic Field Levels With Peak Magnitudes Below The Earth's Magnetic Field, Robert A. Schill, Karin V. Hoff

Electrical & Computer Engineering Faculty Research

Characterizing and calibrating a low impedance large Helmholtz coil generating 60 Hz magnetic fields with amplitudes well below the earth’s magnetic field is difficult and imprecise when coil shielding is not available and noise is an issue. Parameters influencing the calibration process such as temperature and coil impedance need to be figured in the calibration process. A simple and reliable calibration technique is developed and used to measure low amplitude fields over a spatial grid using a standard Hall effect probe gaussmeter. These low amplitude fields are typically hard or impossible to detect in the presence of background fields when …

Inverse Synthetic Aperture Radar Imaging Using A Coherent Ultrawideband Random Noise Radar System, Daryl C. Bell, Ram M. Narayanan

Department of Electrical and Computer Engineering: Faculty Publications

The University of Nebraska-Lincoln has developed an ultrawideband random noise radar operating over the 1- to 2-GHz frequency range. The system uses the technique of heterodyne correlation, and is thus phase coherent. It has therefore been used in applications such as interferometry, polarimetry, and Doppler estimation. This assesses the performance of this radar as a range-Doppler imaging system, in particular, inverse synthetic aperture radar (ISAR). By performing turntable experiments, we examine a number of issues that arise both from the wideband nature of the radar system and from the randomness of the transmit signal. Although the ultrawideband nature of the …

Overview Of Acousto-Optic Bistability, Chaos, And Logical Applications, Monish Ranjan Chatterjee, Erol Sonmez

Electrical and Computer Engineering Faculty Publications

An overview is presented of the key results in the field of acousto-optic bistability in the past two decades. It is shown that the basic acousto-optic bistable device may be described as a nonlinear dynamical system which satisfies a quadratic map. Thereafter, details are presented of several analytical methods, computer modeling approaches, including the SPICE circuit modeling technique, and experiments that have been used to understand the phenomenon.

Extensions to logical and digital applications are also discussed.

Comparison Of Two Distributed Fuzzy Logic Controllers For Flexible-Link Manipulators, Linda Z. Shi, Mohamed Trabia

Mechanical Engineering Faculty Presentations

The paper suggests that fuzzy logic controllers present a computationally efficient and robust alternative to conventional controllers. The paper presents two possible structures for the distributed fuzzy logic controller of a single-link flexible manipulator. A linear quadratic regulator method is used to prove the effectiveness of fuzzy logic controllers.

Aspect Sensitivity Measurements Of Polar Mesosphere Summer Echoes Using Coherent Radar Imaging, P. B. Chilson, T.-Y. Yu, R. D. Palmer, S. Kirkwood

Department of Electrical and Computer Engineering: Faculty Publications

The Esrange VHF radar (ESRAD), located in northern Sweden (67.88) N, 21.10- E), has been used to investigate polar mesosphere summer echoes (PMSE). During July and August of 1998, coherent radar imaging (CRI) was used to study the dynamic evolution of PMSE with high temporal and spatial resolution. A CRI analysis provides an estimate of the angular brightness distribution within the radar’s probing volume. The brightness distribution is directly related to the radar reflectivity. Consequently, these data are used to investigate the aspect sensitivity of PMSE. In addition to the CRI analysis, the full correlation analysis (FCA) is used to …

Locating Target At High Speed Using Image Decimation Decomposition Processing, Zikuan Chen, Mohammad Rezaul Karim, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

We develop a decimation-decomposition processing technique that consists of judiciously selecting certain decimation-decomposed components of an image and then performing inter-component processing. For a (k_x,k_y)-decimation decomposition, there may be up to k_xk_y decimation-decomposed components. The minimal surviving and maximal non-surviving lengths associated with inter-component processing algorithm allows for clutter suppression. By removing detection redundancies, one can locate the target at high speed. A “where-then-what” model is proposed for target tracking and recognition. It locates the target by-image decimation-decomposition processing first and then recognizes the target in question using a suitable image recognition technique.

Cyberpsychology And Virtual Reality: Is An Update Necessary, Ibpp Editor

International Bulletin of Political Psychology

This article explores the notion that something called "human nature" may be changing in an era of significant information technology developments.

The Determination Of Failure Occurring In The Stator Coil Winding Due To The Over-Voltage Using Matlab Software, Ali Reza Alavizadeh

Morehead State Theses and Dissertations

A thesis presented to the faculty of the College of Science & Technology at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science in Vocational Education / Technology by Ali Reza Alavizadeh on January 8, 2001.

Scanner Parameter Estimation Using Bilevel Scans Of Star Charts, Elisa H. Barney Smith

Electrical and Computer Engineering Faculty Publications and Presentations

Scanning a high contrast image in bilevel mode results in image degradation. This is caused by two primary effects: blurring and thresholding. This paper expands on a method of estimating a joint distortion parameter, called the edge spread, from a star sector test chart in order to calculate the values of the point spread function width and binarization threshold. This theory is also described for variations in the source pattern which can represent degradations caused by repetition of the bilevel process as would be seen in printing then scanning, or in repeated photocopying. Estimation results are shown for the basic …

Rules For A Cellular Automaton To Model Quantum-Dot Cellular Automata, Teresa Cole, John C. Lusth

Electrical and Computer Engineering Faculty Publications and Presentations

Quantum-dot cellular automata are one of several new device architectures whose operation is based on local interactions, much like cellular automata. We have implemented several rule sets for a cellular automaton that could be used to model the behavior of quantum-dot cellular automata and used them to test most of the wire and gate configurations proposed for these devices. Arrangements of cells for which any particular cell has neighbors which are not adjacent to each other generally behave as expected. Unfavorable arrangements of cells such as those with bends and crosses tend to either have incorrect outputs or be unstable …

Remote Monitoring System, Chin Kee Tan

Student Works (2000-2009)

Research is conducted to analysis and evaluate about the Remote Monitoring System. The details process of developing the Remote Monitoring System will be discussed throughout whole section of this project. The primary objective of this project is to explore on how Remote Monitoring CCTV process work as well as the application area used in Remote Monitoring CCTV system. This project involves creating a real time monitoring video camera system as a prototype. The developer will perform the development of the system according to system development life cycle. Stages of the system development life cycle for developing the remote monitoring software …

Study Of Dynamics And Mechanism Of Metal-Induced Silicon Growth, Elena A. Guliants, Wayne A. Anderson

Electrical and Computer Engineering Faculty Publications

The present study addresses the mechanism of metal-induced growth of device-quality silicon thin films. Si deposition was performed by magnetron sputtering on a 25-nm-thick Ni prelayer at 525–625 °C and yielded a continuous, highly crystalline film with a columnar structure. A Ni disilicide intermediate layer formed as a result of the Ni reaction with Si deposit provides a sufficient site for the Si epitaxial growth because lattice mismatch is small between the two materials. The reaction between Ni and Si was observed to progress in several stages. The NixSiy phase evolution in a Ni:Si layer was studied by x-ray photoelectron …

Meta-Genetic Programming: Co-Evolving The Operators Of Variation, Bruce Edmonds

Turkish Journal of Electrical Engineering and Computer Sciences

The standard Genetic Programming approach is augmented by co-evolving the genetic operators. To do this the operators are coded as trees of indefinite length. In order for this technique to work, the language that the operators are defined in must be such that it preserves the variation in the base population. This technique can varied by adding further populations of operators and changing which populations act as operators for others, including itself, thus to provide a framework for a whole set of augmented GP techniques. The technique is tested on the parity problem. The pros and cons of the technique …

All-Optical Networking, Altan Koçyi̇ği̇t, Demeter Gökişik, Semi̇h Bi̇lgen

Turkish Journal of Electrical Engineering and Computer Sciences

A survey of recent literature on all optical networking is presented. Starting from multiplexing techniques and topological features, network design and performance issues are reviewed. Particular attention is devoted to Wavelength Division Multiplexing (WDM) networks. Static and dynamic solutions of the routing and wavelength assignment (RWA) problem are considered. Issues of current research are summarized.

An Integrated Design-Object Modeling Environment -- Pluggable Metamodel Mechanism --, Masaharu Yoshioka, Takayuki Sekiya, Tetsuo Tomiyama

Turkish Journal of Electrical Engineering and Computer Sciences

We propose a new integrated computational environment to support design object modeling, during engineering design process that requires a variety of design object models, such as a geometric model, a control model, and a finite element model. To integrate multiple design object models, we have developed a mechanism called a metamodel mechanism that maintains consistency among various models. The metamodel mechanism represents relationships among concepts used in these models and is useful, for example, to conduct concurrent engineering practices. In this framework, we formalize a design process as operations to the metamodel. This paper expands the concept of the metamodel …

Combining Multiple Representations For Pen-Based Handwritten Digit Recognition, Fevzi̇ Ali̇moğlu, Ethem Alpaydin

Turkish Journal of Electrical Engineering and Computer Sciences

We investigate techniques to combine multiple representations of a handwritten digit to increase classification accuracy without significantly increasing system complexity or recognition time. In pen-based recognition, the input is the dynamic movement of the pentip over the pressure sensitive tablet. There is also the image formed as a result of this movement. On a real-world database of handwritten digits containing more than 11,000 handwritten digits, we notice that the two multi-layer perceptron (MLP) based classifiers using these representations make errors on different patterns implying that a suitable combination of the two would lead to higher accuracy. We implement and compare …

Fingerprint Recognition Using Neural Networks, Eng Hoe Kennie Yeoh

Student Works (2000-2009)

Traditional methods of fingerprint verification uses either complicated feature detection algorithms that are not specific to each fingerprint, or compare two fingerprint images directly using image processing toots. The former involves very complicated calculations and tedious algorithms, and the latter tend to work poorly. In this paper it is described a new method which takes the middle ground. This paper studies the implementation of the Fast Fourier Transform and Artificial Neural Networks into the recognition of fingerprints. With tests conducted on the implementation of the Fourier Transform as a method of fingerprint feature extraction, the use of the Fourier Transform …

Atm Lane Simulator, Kim Joo Ching

Student Works (2000-2009)

This project describes the development of ATM Local Area Network Emulation (LANE) simulator components. In LANE, an A TM network is configured to simulate an Ethernet or token ring network and coexist with the legacy network without making any modification to Them.The development of this simulator incorporates several important features. The most important feature of the simulator is that it is build based on object-oriented approach, which is able to provide the benefits of re usability, flexibility and extensibility. The second important feature is that it supports multi threaded operations. This means that every object able to act simultaneously. Besides …

Rekabentuk Perkakasan Khas Ecc (Reed-Solomon), Muhamad Mursid Noorizan

Student Works (2000-2009)

Dokumen ini disiapknn bagi menyediakan laporan tentang perjalanan projek perkakasan khas ECC yang dijalankan. Bahagian pertama dokumen ini terdapat pengenalan tentang projek. Bahagian kedua pula menyatakan tentang kajian yang telah dilakukan bagi memilih kod-kod pembetulan yang ingin dibangunkan. Seterusnya pada bahagian tiga, dinyatakan serba sedikit tentang bahasa yang digunakan dalam pembangunan projek iaitu VHDL. Sahagian keempat pula menceritakan tentang senibina-senibina dan rekabentuk-rekabentuk perkakasan khas. Dalam bahagian lima, dokumen menceritakan tentang fasa pembangunan yang telah dijalankan. Bahagian enam dan tujuh pula menceritakan tentang perbincangan dan kesimpulan daripada projek yang telah dijalankan.