Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Electrical and Computer Engineering

1997

Institution
Keyword
Publication
Publication Type
File Type

Articles 1 - 30 of 217

Full-Text Articles in Engineering

Markovian Decision Control For Traffic Signal Systems, Xiao-Hua Yu, Allen R. Stubberud Dec 1997

Markovian Decision Control For Traffic Signal Systems, Xiao-Hua Yu, Allen R. Stubberud

Electrical Engineering

Setting signals at intersections to minimize the queue length and vehicle delay time is a key goal in traffic management. In this paper, a new control strategy for a signalized traffic intersection is developed by applying Markovian decision control theory. Statistical analysis of simulation results with different arrival rates indicate the excellent potential of this approach.

Go to article

Optimal Block Encoding And Optimal Entropy For Lossless Image Compression, Larry Ray Dennis Dec 1997

Optimal Block Encoding And Optimal Entropy For Lossless Image Compression, Larry Ray Dennis

Dissertations and Theses

In this thesis, a novel approach is designed using a quad-tree stack structure to encode the image to determine the optimal block size at the optimal and effective entropy in the lossless image compression method. Proof is given through encoding of the predictor and randomly constructed planes. There is a high degree of relationship between the placement of bits in the planes. Clearly results shows that use of the optimal entropy and encoding block sizes will increase the compression ratio using the lossless method. The cost of using the block size methods to encoding and entropy is discussed and proven. …

Go to article

The Development Of Electromechanical Batteries For Power System Support And For Short-Term Standby Power, Michael Peter O'Leary Dec 1997

The Development Of Electromechanical Batteries For Power System Support And For Short-Term Standby Power, Michael Peter O'Leary

Masters

The slow move from a fossil-fuel powered society to a renewable-energy powered society is creating and will continue to create a demand for good energy storage techniques. The electromechanical battery (EMB), comprising a flywheel energy storage system with electrical input and output, is one of the many candidate technologies. Two different EMB types are evaluated in this present project. The first is a ring (or annular) flywheel to be constructed using fibre composite materials and to rotate at high speed in a vacuum. Energy is to be imported and exported electromagnetically based on linear electrical machine principles. Confinement of the …

Go to article

Joint Map Registration And High Resolution Image Estimation Using A Sequence Of Undersampled Images, Russell C. Hardie, Kenneth J. Barnard, Ernest E. Armstrong Dec 1997

Joint Map Registration And High Resolution Image Estimation Using A Sequence Of Undersampled Images, Russell C. Hardie, Kenneth J. Barnard, Ernest E. Armstrong

Electrical and Computer Engineering Faculty Publications

n many imaging systems, the detector array is not sufficiently dense to adequately sample the scene with the desired field of view. This is particularly true for many infrared focal plane arrays. Thus, the resulting images may be severely aliased. This paper examines a technique for estimating a high-resolution image, with reduced aliasing, from a sequence of undersampled frames. Several approaches to this problem have been investigated previously. However, in this paper a maximum a posteriori (MAP) framework for jointly estimating image registration parameters and the high-resolution image is presented. Several previous approaches have relied on knowing the registration parameters …

Go to article

Secondary Data Support And Non-Homogeneities In Space-Time Adaptive Processing, Todd B. Hale Dec 1997

Secondary Data Support And Non-Homogeneities In Space-Time Adaptive Processing, Todd B. Hale

Theses and Dissertations

One of the primary problems with the application of Space-Time Adaptive Processing (STAP) techniques is secondary data support for the interference plus noise covariance matrix estimate. Reed has shown the required secondary data support to achieve performance within 3 dB of optimal SINR is approximately equal to twice the degrees of freedom (DOF) used in the algorithm. Reed proved this rule for Sample Matrix Inversion (SMI) techniques. A concern arises when applying this rule to a newer class of reduced dimension STAP algorithms that do not fall under the SMI umbrella. This thesis focuses on the Cross Spectral Metric (CSM) …

Go to article

Micro-Electromechanical Switches For Micro-Satellite Power Transfer, Glen A. Kading Dec 1997

Micro-Electromechanical Switches For Micro-Satellite Power Transfer, Glen A. Kading

Theses and Dissertations

In the past few years, microelectromechanical systems (MEMS) have emerged as a promising new technology with tremendous application potential. One of the possible implementations of MEMS technology is in the development of micro-satellites. It should be possible to mass-produce micro-satellites at a fraction of the cost of one conventional satellite. In order for satellites to be robust, a method of transferring power to systems must be addressed. As micro-satellites are made with conventional integrated circuit technologies at a very small scale, a means of transferring power on a similar scale will be investigated. This research addresses the issue of the …

Go to article

Atmospheric Induced Errors In Space-Time Adaptive Processing, Vinod D. Naga Dec 1997

Atmospheric Induced Errors In Space-Time Adaptive Processing, Vinod D. Naga

Theses and Dissertations

This thesis examines the effects of atmospheric turbulence-induced phase perturbations on the performance of ground-based Space-Time Adaptive Processing (STAP) systems. Both Fully Adaptive Joint Domain Optimum and Partially Adaptive Factored-Time Space processing methods are examined. This thesis concentrates on the turbulence effects on STAP applied to ground-based arrays. This thesis further focuses on the capability of STAP to resolve targets at low elevation angles in the presence of turbulence. Only clutter interference and receiver noise are considered. Turbulence effects on the EM phase-front are calculated for turbulence strength Cn(2) values ranging from 5.0 x 10(exp -14) m-2/3 to 5.0 x …

Go to article

Pressure Impulses During Microsecond Laser Ablation, Hanqun Shangguan, Lee W. Casperson, Scott A. Prahl Dec 1997

Pressure Impulses During Microsecond Laser Ablation, Hanqun Shangguan, Lee W. Casperson, Scott A. Prahl

Electrical and Computer Engineering Faculty Publications and Presentations

The collapse of laser-induced cavitation bubbles creates acoustic transients within the surrounding medium and also pressure impulses to the ablation target and light-delivery fiber during microsecond laser ablation. The impulses are investigated here with time-resolved flash photography, and they are found to occur whether or not the light-delivery fiber is in contact with the target. We demonstrate that the impulses depend primarily on the energy stored in the cavitation bubble. They are not directly dependent on the mode of light delivery (contact versus noncontact), and they are also not directly correlated to the other acoustic transients. The pressure impulses do …

Go to article

New Perspectives For Maximum Likelihood Time-Delay Estimation, John A. Stuller Dec 1997

New Perspectives For Maximum Likelihood Time-Delay Estimation, John A. Stuller

Electrical and Computer Engineering Faculty Research & Creative Works

This Paper Introduces a New Realization for Maximum Likelihood Time-Delay Estimation (TDE) that Illuminates the Relationships between Maximum Likelihood TDE and Other Methods. We Obtain the Result by Deriving the Likelihood Function using a Fundamental Method that Appears to Be New to the Field of Array Processing. This Method is a Natural Complement to the Generalized Karhunen-Loève Expansion. © 1997 IEEE.

Go to article

User Location Determination Strategy In A Low Earth Orbit Satellite Network, Jaehee Lee Dec 1997

User Location Determination Strategy In A Low Earth Orbit Satellite Network, Jaehee Lee

Theses and Dissertations

Recently, many Low Earth Orbit (LEO) satellite systems have been proposed for the purpose of global communication and one of those systems is planned to start the commercial service in 1998. These LEO satellite systems are providing most of current communication services (voice, fax, data, paging, and even real time video service) without any limitation on place and time. However, little is published about their detail system methodology on user tracking and managing schemes. This thesis presents two user location tracking algorithms in a LEO environment. One (Gateway Approach) is the most likely approach under present system proposals, while the …

Go to article

Using Cross-Eye Techniques To Counter Radio Frequency Agile Monopulse Processing, Gregory J. Meyer Dec 1997

Using Cross-Eye Techniques To Counter Radio Frequency Agile Monopulse Processing, Gregory J. Meyer

Theses and Dissertations

The purpose of this research was to evaluate how current cross-eye techniques protect an airborne platform versus a pulse-to-pulse Radio Frequency (RF) agile monopulse processing threat and, if necessary, develop a new cross-eye techniques to counter this threat. This research evaluates how both current retrodirective cross-eye techniques and an original technique, namely synchronized cross-eye, hide the true skin return in the time and frequency domain while preserving the necessary phase interferometric effects at the threat radar location. Existing retrodirective cross-eye techniques are inadequate to counter the RF agile threat due to propagation delays. Using modeling and simulation, the research shows …

Go to article

A Wire Antenna Designed For Space Wave Radiation Over The Earth Using A Genetic Algorithm, Brian S. Sandlin Dec 1997

A Wire Antenna Designed For Space Wave Radiation Over The Earth Using A Genetic Algorithm, Brian S. Sandlin

Theses and Dissertations

A wire antenna is designed for optimal performance at low elevation angles in the presence of a lossy half-space. A simple genetic algorithm (GA) and GENOCOP III software are each integrated with Numerical Electromagnetics Code Version 4.1 (NEC4.1) to optimize a wire antenna geometry for multiple objectives: power gain, azimuthal symmetry, and input impedance. The performance of the two versions of the integrated GA are compared. Several of the resulting antennas are analyzed, and an antenna is proposed for use in a Remote Intrusion Monitoring System (RIMS). Simulations suggest that the proposed antenna, which is well-matched, offers a significant increase …

Go to article

Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler Dec 1997

Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler

Theses and Dissertations

An understanding of spontaneous emission processes within microcavities is crucial in addressing the need to make tomorrow's microlasers more efficient. One approach to improving the device efficiency is to reduce the threshold input energy at which lasing begins to occur. It has been suggested that the threshold in a microcavity laser can be decreased by increasing the fraction of spontaneous emission into the lasing mode, this can be accomplished by preferentially coupling the gain medium of the laser to the electromagnetic cavity mode of interest. It therefore becomes necessary to understand the mechanism by which this coupling takes place. This …

Go to article

A Dispersive Scattering Center, Parametric Model For 1-D Atr, Dane F. Fuller Dec 1997

A Dispersive Scattering Center, Parametric Model For 1-D Atr, Dane F. Fuller

Theses and Dissertations

The dispersive scattering center (DSC) model characterizes high-frequency backscatter from radar targets as a finite sum of localized scattering geometries distributed in range, these geometries, along with their relative locations, can be conveniently used as features in a one-dimensional automatic target recognition (ATR) algorithm. The DSC model's type and range parameters correspond to geometry and distance features according to the geometric theory of diffraction (GTD). Since these parameters are estimated in the phase history domain of the radar signal, the range parameter does provide superresolution in the time domain. To demonstrate the viability of feature extraction based on the DSC …

Go to article

A Comparative Analysis Of Networks Of Workstations And Massively Parallel Processors For Signal Processing, David C. Gindhart Dec 1997

A Comparative Analysis Of Networks Of Workstations And Massively Parallel Processors For Signal Processing, David C. Gindhart

Theses and Dissertations

The traditional approach to parallel processing has been to use Massively Parallel Processors (MPPs). An alternative design is commercial-off-the-shelf (COTS) workstations connected to high-speed networks. These networks of workstations (NOWs) typically have faster processors, heterogeneous environments, and most importantly, offer a lower per node cost. This thesis compares the performance of MPPs and NOWs for the two-dimensional fast Fourier transform (2-D FFT). Three original, high-performance, portable 2-D FFTs have been implemented: the vector-radix, row-column and pipeline. The performance of these algorithms was measured on the Intel Paragon, IBM SP2 and the AFIT NOW, which consists of 6 Sun Ultra workstations …

Go to article

Evaluation Of A Maximum A-Posteriori Slope Estimator For A Hartmann Wavefront Sensor, Troy B. Van Caster Dec 1997

Evaluation Of A Maximum A-Posteriori Slope Estimator For A Hartmann Wavefront Sensor, Troy B. Van Caster

Theses and Dissertations

Current methods for estimating the wavefront slope at the aperture of a telescope using a Hartmann wavefront sensor are based upon a centroid shift estimator. The centroid shift estimator determines the displacement, or shift, of the centroid off the optical axis using a moment calculation of the intensity distributions recorded in each subaperture. This centroid shift is proportional to the average slope of the wavefront in each subaperture. A maximum a-posteriori (MAP) slope estimator takes advantage of a-priori knowledge of the wavefront slope statistics and total irradiance falling on the subaperture detector arrays when determining the shift estimate. In order …

Go to article

The Rational Resolution Analysis: A Generalization Of Multi-Resolution Analyses With Application To To The Specific Emitter Identification Problem, Bruce P. Anderson Dec 1997

The Rational Resolution Analysis: A Generalization Of Multi-Resolution Analyses With Application To To The Specific Emitter Identification Problem, Bruce P. Anderson

Theses and Dissertations

The rational resolution analysis RRA is introduced and developed as a generalization of the integer, dilation multiresolution analyses MRA developed by Mallat and Meyer. Rational dilation factors are achieved by relaxing the condition on MRAs that successive approximation spaces be embedded. Conditions for perfect reconstruction are discussed and it is shown that perfect reconstruction is possible with specific constraints on the scaling function the scaling filter must have its roots on the unit circle. Furthermore, the required arrangement of the roots indicate the scaling function must be derived from a B-spline of some degree. It is proven the only compactly …

Go to article

A Gps Code Tracking Receiver Design For Multipath Mitigation Using Maximum Likelihood Estimation, Fred P. Baier Dec 1997

A Gps Code Tracking Receiver Design For Multipath Mitigation Using Maximum Likelihood Estimation, Fred P. Baier

Theses and Dissertations

The NAVSTAR Global Positioning System (GPS) is currently used in many applications requiring precise positioning data. Improving the precise positioning information requires the removal of errors that perturb the received signals. The errors introduced by multiple propagation channels, termed multipath, are not easily removed. These channels are caused by reflective surfaces near the receiver. As such, multipath is uncorrelated between receivers and, thus, cannot be removed through differencing techniques. This thesis investigates a GPS code tracking loop design which uses maximum likelihood (ML) estimation to determine amplitude and phase information of the multipath signal which are used to adjust code …

Go to article

Microelectromechanical Scanner Using A Vertical Cavity Surface Emitting Laser, Joseph G. Bouchard Jr. Dec 1997

Microelectromechanical Scanner Using A Vertical Cavity Surface Emitting Laser, Joseph G. Bouchard Jr.

Theses and Dissertations

Optical scanners play a prominent role in the commercial and military industries. The scanner's size, cost and reliability are critical characteristics. In this research a microoptical scanning system was fabricated by incorporating a vertical cavity surface emitting laser (VCSEL) onto a surface machined microelectromechanical die. The micro optics for laser beam steering includes a 135 deg mirror, a Fresnel lens, a lateral scanning rotating mirror, and a vertical scanning fan mirror. The VCSEL was attached to the die by solder and electrical connection was provided by wire bonding. Based on far field measurements the scanner had a lateral scan angle …

Go to article

Visualization And Animation Of A Missile/Target Encounter, Jeffrey T. Bush Dec 1997

Visualization And Animation Of A Missile/Target Encounter, Jeffrey T. Bush

Theses and Dissertations

Existing missile/target encounter modeling and simulation systems focus on improving probability of kill models. Little research has been done to visualize these encounters. These systems can be made more useful to the engineers by incorporating current computer graphics technology for visualizing and animating the encounter. Our research has been to develop a graphical simulation package for visualizing both endgame and full fly-out encounters. Endgame visualization includes showing the interaction of a missile, its fuze cone proximity sensors, and its target during the final fraction of a second of the missile/target encounter. Additionally, this system displays dynamic effects such as the …

Go to article

Multiple Model Adaptive Estimation And Control Redistribution Performance On The Vista F-16 During Partial Actuator Impairments, Curtis S. Clark Dec 1997

Multiple Model Adaptive Estimation And Control Redistribution Performance On The Vista F-16 During Partial Actuator Impairments, Curtis S. Clark

Theses and Dissertations

Multiple Model Adaptive Estimation with Control Reconfiguration (MMAE/CR) capability to estimate and compensate for partial actuator failures, or "impairments" is investigated using the high-fidelity, nonlinear, six-degree-of-freedom, VISTA F-16 simulation which currently resides on the Simulation Rapid-Prototyping Facility (SRF). After developing a model for inserting partial actuator impairments into the VISTA F-16 truth model, research begins with a battery of single actuator impairment tests. This stage of research explores the capability of the existing MMAE algorithm to estimate single, partial actuator impairments, and helps to define refinements and expansions needed in the MMAE algorithm for the second phase of research: the …

Go to article

Analytic Transfer Function Of The Forward Propagation Of Diffuse Photon Density Waves In Turbid Media With An Embedded Spherical Inhomogeneity, Deborah L. Lasocki Dec 1997

Analytic Transfer Function Of The Forward Propagation Of Diffuse Photon Density Waves In Turbid Media With An Embedded Spherical Inhomogeneity, Deborah L. Lasocki

Theses and Dissertations

Diffusing photons can be used to detect and localize optical inhomogeneities embedded in turbid media such as clouds, fog, paint and human tissue. This thesis shows that a transfer function derived from an analytic solution of the Helmholtz equation can completely characterize in three dimensions the perturbations in the forward propagation phenomena caused by a spherical defect object in a multiple-scattering medium. Two models of the forward propagation behavior of diffuse photon density waves in homogeneous, infinite, turbid media that contains a spherical inhomogeneity are examined. The first model is an exact analytic solution based on a modal expansion in …

Go to article

Speaker Verification In The Presence Of Channel Mismatch Using Gaussian Mixture Models, Robert B. Reid Dec 1997

Speaker Verification In The Presence Of Channel Mismatch Using Gaussian Mixture Models, Robert B. Reid

Theses and Dissertations

A channel compensation method is sought for use in speaker identification (ID) and verification applications under matched and mismatched training and testing conditions. This work expands on previous work on matched conditions by investigating three techniques on matched and mismatched conditions using the TIMIT and NTIMIT speech databases. First, previous results on 168 speakers are reproduced for matched conditions using Gaussian mixture models (GMM) and mel-frequency cepstral coefficients. Next, cepstral mean subtraction with band limiting (CMSBL) is investigated. The third method, developed in this thesis uses a modified Wiener filtering approach to channel compensation. New GMMs are created for each …

Go to article

Scattering From Dielectric Bodies, Jeffery M. Parks Dec 1997

Scattering From Dielectric Bodies, Jeffery M. Parks

Theses and Dissertations

The purpose of this study was to develop an RCS measured database of non-PEC targets and provide an example of its use to validate a code, 3D-RCIE. RCS prediction codes that handle penetrable materials require measured data to determine their accuracy. The materials used for this research include polyethylene and polyurethane with dielectric constants around 2.3 and 1.03, respectively. The polyethylene targets include a mini-arrow, ogive, conesphere, conesphere with a gap, sphere, and a large and small cube. The cubes were the only targets made from the polyurethane foam. Additionally, r-card was applied to the cubes and mini-arrow. The material …

Go to article

Breast Cancer Mass Detection Using Difference Of Gaussians And Pulse Coupled Neural Networks, Donald A. Cournoyer Dec 1997

Breast Cancer Mass Detection Using Difference Of Gaussians And Pulse Coupled Neural Networks, Donald A. Cournoyer

Theses and Dissertations

CAD, serving as a second reader, has been shown to improve the success of radiologists at detecting breast cancer. This thesis will develop a new algorithm to identify masses in mammograms. The system developed for this thesis will be capable of assisting a radiologist in making decisions.

Go to article

Applications Of Unsupervised Clustering Algorithms To Aircraft Identification Using High Range Resolution Radar, Dzung Tri Pham Dec 1997

Applications Of Unsupervised Clustering Algorithms To Aircraft Identification Using High Range Resolution Radar, Dzung Tri Pham

Theses and Dissertations

Identification of aircraft from high range resolution (HRR) radar range profiles requires a database of information capturing the variability of the individual range profiles as a function of viewing aspect. This database can be a collection of individual signatures or a collection of average signatures distributed over the region of viewing aspect of interest. An efficient database is one which captures the intrinsic variability of the HRR signatures without either excessive redundancy typical of single-signature databases, or without the loss of information common when averaging arbitrary groups of signatures. The identification of 'natural' clustering of similar HRR signatures provides a …

Go to article

Effects Of Near-Field Scatterers On Space-Time Adaptive Processing, Jonathan W. Fitton Dec 1997

Effects Of Near-Field Scatterers On Space-Time Adaptive Processing, Jonathan W. Fitton

Theses and Dissertations

Near-field scatterers, such as the wing of an airplane, can affect the ability of the processor to null out clutter and jammer signals. The target, clutter, and jammer signals will reflect off the near-field scatterers into the array and appear to be coming from a direction different from their true sources. This thesis develops a theoretical model for the direct path and scattered path signals from the target, clutter, and jamming signals. The optimum weight vector, normally computed using the steering vector to the target and the covariance matrix of the undesired signals, must now include the effects of the …

Go to article

Optimized Design Methodology Of Cavity-Backed Microstrip Antennas With Dielectric Overlays, Douglas J. Hermes Dec 1997

Optimized Design Methodology Of Cavity-Backed Microstrip Antennas With Dielectric Overlays, Douglas J. Hermes

Theses and Dissertations

The optimized design methodology implemented in this research employs a design methodology, namely Response Surface Methodology (RSM), that is relatively new to the electromagnetics field. The design methodology used a full factorial designed experiment, a Hybrid Finite Element Method (HFEM) analysis code, a cubic spline empirical model, an Analysis of Variance (ANOVA) test, and a simplex optimization code to successfully measure, predict, analyze, and optimize average antenna gain and antenna input impedance for a cavity backed microstrip antenna with dielectric overlays. Based on HFEM results from the full factorial designed experiment, a cubic spline empirical model successfully predicted average antenna …

Go to article

A Single Chip Low Power Implementation Of An Asynchronous Fft Algorithm For Space Applications, Bruce W. Hunt Dec 1997

A Single Chip Low Power Implementation Of An Asynchronous Fft Algorithm For Space Applications, Bruce W. Hunt

Theses and Dissertations

A fully asynchronous fixed point FFT processor is introduced for low power space applications. The architecture is based on an algorithm developed by Suter and Stevens specifically for a low power implementation. The novelty of this architecture lies in its high localization of components and pipelining with no need to share a global memory. High throughput is attained using large numbers of small, local components working in parallel. A derivation of the algorithm from the discrete Fourier transform is presented followed by a discussion of circuit design parameters specifically, those relevant to space applications. The generic architecture is explained with …

Go to article

Atmospheric Turbulence Scintillation Effects On Wavefront Tilt Estimation, James A. Louthain Dec 1997

Atmospheric Turbulence Scintillation Effects On Wavefront Tilt Estimation, James A. Louthain

Theses and Dissertations

A new atmospheric turbulence screen generator is developed for use in performance calculations of adaptive optics systems valid over a wide range of atmospheric turbulence parameters. The screen generator accounts for diffraction effects caused by weak turbulence and incorporates the phase, amplitude, and cross statistics of the perturbed optical field. The wavefront's phase and amplitude perturbations are taken from the correlation functions developed by Lee and Harp and the cross correlation of the phase and amplitude derived in this thesis. The screen generator uses a modal representation to perform a Fourier series expansion of the wavefront phase and amplitude over …

Go to article

Next Last