Digital Commons Network^™

Dynamic Behavior Of Co₂ Lasers, Li Zhang

Dissertations and Theses

Spontaneous pulsations have been observed in the output of a CO₂ laser. The temporal waveforms, transverse mode patterns, and laser lines are simultaneously measured under various operation conditions. The experimental data show that these pulsations have a direct connection with the transverse modes. We interpret the oscillations as being caused by mode beating, and the frequency shift of the oscillation as resulting from mode pulling. The theoretical explanations for these effects are in good agreement with the experimental results.

Endless State-Of-Polarization Control For Coherent Optical Communication Systems Using Nematic Liquid Crystal, Scott H. Rumbaugh

Dissertations and Theses

One of the obstacles to coherent fiber-optic communications is the unpredictable polarization drift which necessitates the use of an active polarization controlling system to match the polarizations of the signal and local oscillator. The polarization match must be maintained during the reset of any of the finite range components to prevent loss of data. We present a novel and practical system which uses three liquid crystal devices for the polarization matching process. Also, the required reset control algorithm and its derivation are described in detail.

Propagation Of Millimeter Wave Signals In Forests Using The Equation Of Radiative Transfer With Strong Forward Scattering Phase Functions, Nack Yang Cho

Dissertations

A forest is a highly scattering medium at millimeter wave frequencies. The propagation of cw millimeter wave signals in forests has been studied previously, both theoretically and experimentally. Published experimental data verified that continuous wave transmission is possible over lengths of the order of a few hundred meters and that a forest acts to strongly scatter energy in the forward direction. The cw studies yielded the determination of the range dependence, beam broadening effects and depolarization effects of millimeter wave signals in a forest. However, pulse broadening effects, which are of importance particularly in the case of digital signal transmission, …

An Approach To Pattern Recognition Of Multifont Printed Alphabet Using Conceptual Graph Theory And Neural Networks, Ihab A. Harb

Dissertations and Theses

This thesis describes an approach for accomplishing a pattern recognition task using conceptual graph theory and neural networks (NNs). The set of patterns to be recognized are the capital letters of six different fonts of the English alphabet, plus two shifted and six rotated versions of each. The letters are represented to the neural network on a 16x16 input grid (256 "sensor lines"). A standard classification encoding for such patterns is to use a 26-bit vector (26 lines at the NN's output), one bit corresponding to each letter. Experiments with such an encoding yielded results with poor generalization capability. A …

Fault-Tolerant Interconnection Networks For Multiprocessor Systems, Hamed Mohamed Nassar

Dissertations

Interconnection networks represent the backbone of multiprocessor systems. A failure in the network, therefore, could seriously degrade the system performance. For this reason, fault tolerance has been regarded as a major consideration in interconnection network design. This thesis presents two novel techniques to provide fault tolerance capabilities to three major networks: the Baseline network, the Benes network and the Clos network.

First, the Simple Fault Tolerance Technique (SFT) is presented. The SFT technique is in fact the result of merging two widely known interconnection mechanisms: a normal interconnection network and a shared bus. This technique is most suitable for networks …

Computer Controlled Oxygen Bioreactor, Dinesh Sachdeva

Theses

A computer controlled oxygen bioreactor has been designed to obtain more accurate values for oxygen bioreactor requirements and to optimize oxygen productivity with respect to oxygen concentration. This study solves a specific problem relating to oxygen concentration measurement and bioreactor control. The proposed reactor system is computer controlled to insure a desired oxygen concentration supply to an oxygen consuming reaction or organism. This thesis also explains and illustrates the bioreactor and its computer control system.

The computer controller incorporates oxygen sensing, oxygen measurement and temperature measurement, Electrical circuits have been designed and built for proper signal conditioning, data acquisition, data …

Integrated Voice/Data Services On Multihop Radio Networks, Chialun Lu

Theses

Integrated voice/data is the first step toward Integrated Services Digital Networks (ISDN). Various techniques have been proposed and analyzed for multiplexing voice and data over a large bandwidth channel. Network efficiency is what we are most concerned about. In this paper, we address the problem of determining optimal access policies for a tandem ISDN network by using Dynamic Programming. Computer simulation shows that optimal policy minimizes the data delay.

Statistical Multiplexing Of Video Sources For Packet Switching Networks, Krishna Kancherla

Theses

Communication networks are fast evolving towards truly integrated networks handling all types of traffic. They employ integrated switching technologies for voice. video and data. Statistical or asynchronous time division multiplexing of full motion video sources is an initial step towards packetized video networks. The main goal is to utilize the common communication channel efficiently, without loosing quality at the receiver. This work discusses the concept of using statistical multiplexing for packet video communications. The topology of a single internal packet network to support ISDN services has been adopted. Simulations have been carried out to demonstrate the statistical smoothing effect of …

Rays And Beams Near The Shadow Boundary, Weixing Gao

Theses

Asymptotic techniques in wave propagation problems exhibit attractive features in computational aspects compared to numerical methods. However, they experience problems in complicated environments due to the transition regions associated with them. The transition region involving a shadow boundary in the downward refractive index profile has been investigated. The ray paths were determined solving the ray equation analytically. The Green's function due to a line source is constructed and evaluated using numerical integration (reference solution) and asymptotic techniques. Then, the field produced by the source, is synthesized, using superposition of beams generated from complex source point representation. The floating parameters such …

Reduced Complexity Receivers For Trellis Coded Modulations Via Punctured Trellis Codes, Bonchul Koo

Theses

We introduce a new concept, called matched punctured trellis encoding, that simplifies the complexity of Maximum Likelihood Sequence Estimation (MLSE) receivers for combined trellis encoding and modulations with memory. Matched punctured trellis encoding is applied to tamed frequency modulation (TFM) which is a bandwidth efficient correlative - FM scheme. TFM finds applications in satellite, microwave radio, and mobile communications.

Our approach is based on puncturing a rate - 1/2 matched convolutional code to obtain a rate - 2/3 mismatched code. A matched code is one that produces trellis coded modulations of minimum complexity. Puncturing these codes to obtain mismatched codes …

Schottky-Barrier Solar Cells, Surface Patterning For Efficient Light Collection, Constantinos Manolis

Theses

Different geometrical surface configurations are considered here for a Au/n-Si semiconductor Schottky-barrier solar cell to improve their light collection efficiency.

Optical and electrical properties are theoretically analyzed for two given optical wavelengths of 0.9 and 0.5 micrometers respectively.

The configurations considered are: V-shaped, Star- shaped, M-shaped, asymmetric-V-shaped, and asymmetric-M-shaped. They all show a significant improvement in the short-circuit current over a flat cell model, while the open-circuit voltage remains practically unchanged.

The Application Of The Ordered List Method And The Dynamic Programming To The Unit Commitment, Hoang Uong

Dissertations and Theses

The thesis presents a method of committing generating units in a hydro-thermal power system within practical computer resources such as computer time and data storage.

Microprocessor Based Protection Of Induction Motors Using Thermal, Mechanical, And Skin Effect Electrical Models To Predict Motor Temperature Rise, Nader S. Moharari

Masters Theses and Doctoral Dissertations

This study investigates induction motor performance during a variety of system and load conditions. A computer simulation is used to characterize the motor behavior during normal operation, lockedrotor case, high inertia loading, and overloading conditions. Motor temperature at critical points is estimated. A microprocessor protection scheme based on motor temperature is proposed. Previous studies assume a linear relationship between motor impedance and frequency when calculating motor temperature. In this study an electrical model, based on Maxwell's equations, is used in conjunction with a mechanical model, to represent the motor during dynamic state conditions. The model accounts for the rotor bar …

Characterization Of The Emission Properties Of Thermographic Phosphors For Use In High Temperature Sensing Applications, Alan Ronald Bugos

Masters Theses

Emission properties of fifteen different powder and crystalline thermographic phosphors have been characterized for potential use in high temperature sensing applications. Excitation and emission spectra of these rare-earth activated thermographic phosphors have been measured as a function of temperature using a special mini oven built inside of a fluorescence spectrophotometer. Several of the thermophosphors underwent decay lifetime analysis and were calibrated for use in high temperature measurements.

The excitation spectra taken from room temperature to approximately 400°C, reveal that the phosphors Y₂O₃:Eu³⁺, YV0₄:Eu³⁺, Ba₃(P0₄)₂:Eu …

Discovery Of Strong Coupling Between Lattice-Band Carriers And Impurity-Band Carriers In Augmented Photoconductivity Measurements On Si:As, Si:Bi, And Si:Al At 7-16 K, James Edward Heath

Electrical and Computer Engineering ETDs

In this work, low-temperature photoconductivity measurements using excitation in the long-wavelength infrared were performed in conjunction with infrared-blocked band-gap excitation in the first studies of the energy transfer between carriers moving in lattice bands and those associated with an impurity band in a semiconductor. Extrinsic (impurity-band) excitations were produced in Si:As, Si:Bi, and Si:Al detectors by infrared photoexcitation at 29-33.5 μm wavelengths (37-43 meV); this could be augmented by simultaneous intrinsic (band-gap) photoexcitation using infrared-blocked white light to inject lattice-band carriers. Carrier transport was induced by applied electric fields of 35-175 V /cm. The experiments were performed at temperatures of …

A Finite State Machine Synthesizer, Jiuling Liu

Dissertations and Theses

This thesis presents a Finite State Machine (FSM) Synthesizer developed at Portland State University. The synthesizer starts from a high level behavioral description, in which no states are specified, and generates the lower level FSM descriptions for simulation and physical layout generation.

Performance Modeling And Enhancement For The Atamm Data Flow Architecture, Sukhamoy Som

Electrical & Computer Engineering Theses & Dissertations

Algorithm To Architecture Mapping Model (ATAMM) is a new marked graph model from which the rules for data and control flow in a homogeneous, multicomputer, data flow architecture may be defined. This research is concerned with performance modeling and performance enhancement for periodic execution of large-grain, decision-free algorithms in such an ATAMM defined architecture. Performance measures and bounds are established. Algorithm transformation techniques are identified for performance enhancement and reduction of computing element requirements. Operating strategies are developed for optimum time performance and for sub-optimum time performance under limited availability of computing elements. An ATAMM simulator is used to test …

Study Of Direct Semiconductor Materials For An Optically Controlled Switch, Sung Taek Ko

Electrical & Computer Engineering Theses & Dissertations

A model for a bulk GaAs photoconductive switch has been developed and solved to determine the performance of the device in closing and opening switch applications. The GaAs material has been characterized by deep level transient spectroscopy (DLTS). Two electron traps (EL2 and EL5) and one hole trap (Cu_B} have been detected and were included in the model. Simulation studies are performed on several GaAs switch systems composed of different combinations and density of deep levels to investigate the influence of deep traps in a photoconductive switch system. The electron occupancy of each deep trap is traced in …

Application Of Hough Transformation To Detect Ovulatory Patterns In Cervical Mucus Images, Shiliang Wang

Dissertations and Theses

A microcomputer system called ovulocomputer is proposed. The system is used to predict and detect ovulation of women. It will use image processing and analysis, pattern recognition theory, spectrophotometry, ionometry and conductometry to measure various physical and chemical properties of cervical mucus that are related to blood hormone levels.

The functions and characteristics of cervical mucus are introduced in this thesis. Among them, the identification of cervical mucus images, named the ferning test, and related features, are well described.

A new idea, called ferning test automation, which has been neither proposed nor developed before, is presented and explained in detail …

The Effects Of Bandwidth Limiting Tuning Elements On A Synchronously Pumped Mode-Locked Dye Laser, Bahram Zandi

Dissertations and Theses

In this study an improved description of the bandwidth limiting tuning filters has been introduced into a semiclassical model for a synchronously pumped mode-locked dye laser system. This model is an improvement over the traditional rate equation approach since it has detailed representations of the energy levels, rotational distribution, and coherence effects. The new set of equations has been solved numerically using the best available values for the various parameters, and autocorrelations have been computed for a range of different length detuning and bandwidth limiting elements. In the experiments, an acousto-optically mode-locked argon ion laser is used to synchronously pump …

Parallel Architectures For Solving Combinatorial Problems Of Logic Design, Phuong Minh Ho

Dissertations and Theses

This thesis presents a new, practical approach to solve various NP-hard combinatorial problems of logic synthesis, logic programming, graph theory and related areas. A problem to be solved is polynomially time reduced to one of several generic combinatorial problems which can be expressed in the form of the Generalized Propositional Formula (GPF) : a Boolean product of clauses, where each clause is a sum of products of negated or non-negated literals.

Invariant Pattern Recognition Algorithm Using The Hough Transform, Duwang Li

Dissertations and Theses

A new algorithm is proposed which uses the Hough Transform to recognize two dimensional objects independent of their orientations, sizes and locations. The binary image of an object is represented by a set of straight lines. Features of the straight lines, namely the lengths and the angles of their normals, their lengths and the end point positions are extracted using the Hough Transform. A data structure for the extracted lines is constructed so that it is efficient to match the features of the lines of one object to those of another object, and determine if one object is a rotated …

A Charge Simulation Based Computer-Aided Design Implementation Of High Voltage Systems Modelling, Hanafy Mahmoud Ismail

Electronic Theses and Dissertations

A Charge Simulation based Computer-Aided Design (CAD) Package which facilitates the development of a charge simulation model for high voltage (HV) systems consisting of a number of electrodes and one or two dielectric regions has been developed. The package calculates the potential and electric field distributions for practical systems. It avoids the necessity for creating individual programs for each system studied by allowing the geometry to be specified using a minimum of entered data. The application of the CAD package to several electrode systems which have analytical solutions is presented. Good agreement, generally within 0.5% was found between the fields …

A Pulsed Field-Gradient System For Nuclear Magnetic Resonance Diffusion Experiments, Saumil Shirish Mehta

Masters Theses

"The construction and performance of a system to generate pulsed magnetic field gradients for use with a commercial superconducting NMR spectrometer for the purpose of molecular self-diffusion measurements is described. Types of coils that provide linear field gradients are discussed. The design and construction of a conventional Helmholtz pair is outlined. A procedure to estimate the magnitude of the field gradients generated by the Helmholtz coils is explained. The design of a circuit to generate fast current pulses using a power MOSFET has been detailed and compared with a functionally similar circuit using bipolar power transistors. The performance of the …

Expansion Of An Existing Power System - A Study, Suresh Arunachalam

Masters Theses

"An existing paper mill is being expanded to increase its installed capacity. Concurrent expansions will be increasing the electrical demand by 40 - 50 MVA. The expansion also includes the addition of DC drives. The existing system has to be used effectively while additional equipment may be added to cater the load increase. Load flow study with various single line diagram configurations has been carried out to find the required solution. A harmonic analysis was also carried out on the suggested new system to install the required filters and capacitor blanks"--Abstract, page ii.

A 68000-Based Produce Sorting Microcomputer : Graduate Clinical Research Master's Report, Ramzi Albert Haidamus

University of the Pacific Theses and Dissertations

This report discusses in great detail the various research, design, and development stages of the Produce Sorting Microcomputer developed for HAGAN ENGINEERING Inc. The two-semester Clinical Research project has been approved by the graduate committee at the School of Engineering at the University of the Pacific and fulfills the requirements towards a Master Degree in Electrical Engineering.

The project was selected based on its complexity, feasibility, the time span it required to complete, and its relevance to the area of real time microcomputer design. In addition, the design constraints and specifications were to be dictated solely by HAGAN ENGINEERING Inc. …

Design Of The Electronics And Optics Needed To Support Charge-Coupled Devices : A Project Report ..., Kah Yep Zee

University of the Pacific Theses and Dissertations

Over the last five years, charge-coupled devices (CCD) have been improved dramatically in terms of sensitivity, manufacturability and particularly, cost. This has enabled them to be used economically in many more industrial and commercial electronic imaging processes. They are found in products ranging from video cameras to satellite-based camera systems. This has sparked my interests in these devices, and with a great deal of encouragement from Dr. Turpin, I decided to base my Master's thesis/project on a CCD. The project was mainly based on the design of the electronics and optics needed to support a CCD. The particular circuit design …

Dsign Of I-D Recursive Digital Filters With Linear Phase Using Two All-Pass Filters With/Without Integer Coefficients, Yoon Ho Kim

Electronic Theses and Dissertations

Digital signal processing is becoming increasingly important, and is finding applications in speech processing and telecommunications in the area of 1-D signal processing. One of the important branches 1n digital signal processing 1s digital filtering.

Among the numbers of structure of digital filters, the recursive(IIR) filter is known for its computational efficiency compared to the FIR counterparts.

In this thesis, an alternative approach to the direct design of 1-D recursive digital filters satisfying prescribed magnitude specifications with or without constant group delay characteristic using two all-pass filters is presented. It is known that, by this approach, the most computationally efficient …

A New Approach To State Minimization Of Finite State Machines, William Yue Zhao

Dissertations and Theses

A complete program to ease the task of large scale Finite State Machine (FSM) minimization presented in this thesis: TDFM (Two Dimensional FSM Minimizer), is a part of the DIADES system. DIADES is an Automatic Design Synthesis System whose development in the Department of Electrical Engineering at Portland State University is supported in part by a research grant from SHARP Microelectronics Technology.

Speech Synthesis Using A Digital Modulation Scheme On The Ibm Personal Computer, John Glenn Wallace

Masters Theses

"Previously the primary output interface that users of personal computers have had available to them were limited to the crt or the printer. This paper presents a method for implementing a voice synthesizer on an IBM personal computer using only the hardware already contained in the personal computer. Presented is a modulation method which can be used with the IBM to obtain good quality voice output. The method consists of 3 parts, 1) sampling and recording the voice, 2) processing and filtering these samples and 3) using these processed samples to drive the speaker. A description of the hardware used …