Engineering Commons^™

Roc Analysis Of Ir Segmentation Techniques, Georgia K. Harrup

Theses and Dissertations

Receiver Operating Characteristic (ROC) curves are used to compare the effectiveness of IR image processing techniques. Two non-parametric error estimation techniques (k-Nearest Neighbor and Parzen Window) are used to create estimates of the probability density functions for the data. These pdfs are used in the creation of the ROC curves for both resubstitution and leave-one-out estimates. These estimates generate the upper and lower bounds, respectively, on the ROC curves. The ROC curve analysis is performed on the outputs of various image processing techniques and the resulting ROC curves are used to compare the techniques. Of the image processing techniques used …

Polarization Sensitivity Of Monopulse Radar Boresight Error Induced By Large, Ogive Radomes, Kelce S. Wilson

Theses and Dissertations

The dependence of Boresight Error (BSE) on incident Electric Field (E-Field) polarization tilt angle is investigated. BSE, defined as the angular difference between a target's actual and radar-indicated position, is influenced by the radome used to protect the antenna. A - reliable computer model for predicting the BSE of electrically large radar-radome systems has been demonstrated and used to investigate the dependence of radome-induced BSE for various combinations of scan angle, element polarization, and incident E-Field polarization. The analysis includes a development of a transmission-depolarization model to justify the results of the computer model. Results compare very well with empirical, …

Experimental Definition For Implantation Of The Afit Cortical Multielectrode Array, Adam G. Spenik

Theses and Dissertations

A two-dimensional multiplexed array of 256 electrodes (16 x 16) has been fabricated using conventional CMOS fabrication techniques. The size and spacing of the electrodes (160 x 160 µm squares with center-to-center spacing of 250 µm) approximate that of the cortical columns. The device is mounted on a small biocompatible package and a protocol to implant this package on the visual cortex of a ferret and a Rhesus monkey was developed and approved. An instrumentation setup to record the data from the device is described as well as the methods used to demultiplex the data. Testing of the device in …

Head Related Transfer Function Approximation Using Neural Networks, John K. Millhouse

Theses and Dissertations

This thesis determines whether an artificial neural network (ANN) can approximate the Armstrong Aerospace Medical Research Laboratories (AAMRL) head related transfer functions (HRTF) data obtained from research at AAMRL during the fall of 1988. The first test determines whether HRTF lends any support in sound localization when compared to no HRTF (Interaural Time Delay only). There is a statistically significant interaction between the location of the sound and whether the HRTF or no HRTF is used. When this interaction is removed using the alternate F.Value, the statistics give the result of equal means for the filters and azimuth. This means …

Adaptive Beamforming In Frequency-Dispersive Multipath Environments, David A. Murray

Theses and Dissertations

It is well known that an antenna array with N degrees of freedom (DOF) can cancel N - 1 interferers if they approach the array from directions other than that of the desired signal. It has been shown that there are cases in which it is possible for an array with N DOF to effectively cancel more than N - 1 interferers. Specifically, we show how this can be done when there is incident upon an N-element array not only the desired signal and a jammer signal, but more than N - 1 Doppler-shifted multipath copies of the jammer signal …

Silicon Based Microactuators For Telerobotic Tactile Stimulation, Britton C. Read Iii

Theses and Dissertations

Silicon based microelectromechanical (MEM) devices using both surface and bulk micromachining have been realized to provide tactile stimulation. The bulk MEM devices utilize the bimorph principle and are fabricated in a complementary metal oxide semiconductor (CMOS) process through MOS implementation system (MOSIS). The surface MEM devices utilize the electrostatic principle and are fabricated in a complementary metal oxide semiconductor (CMOS) process through MOS implementation system (MOSIS). The surface MEM devices utilize the electrostatic principle and are fabricated in the multi-user MEM process (MUMPS) through MCNC. Eleven major designs are presented and tested to determine if they are suitable to provide …

Multiclassifier Fusion Of An Ultrasonic Lip Reader In Automatic Speech Recognition, David L. Jennnings

Theses and Dissertations

This thesis investigates the use of two active ultrasonic devices in collecting lip information for performing and enhancing automatic speech recognition. The two devices explored are called the 'Ultrasonic Mike' and the 'Lip Lock Loop.' The devices are tested in a speaker dependent isolated word recognition task with a vocabulary consisting of the spoken digits from zero to nine. Two automatic lip readers are designed and tested based on the output of the ultrasonic devices. The automatic lip readers use template matching and dynamic time warping to determine the best candidate for a given test utterance. The automatic lip readers …

Electro-Hydrostatic Actuator Controller Design Using Quantitative Feedback Theory, Ki Ho Kang

Theses and Dissertations

The Electro-Hydrostatic Actuator (EllA) technology offers a higher degree of combat survivability and easier maintainability of the aircraft flight control system, because all the components necessary to operate the actuator are collocated with the actuator. Quantitative Feedback Theory (QFT) is used to design a control system for the EHA. The impact of parameter variations, sensor noise, and flight conditions are explicitly considered in the design process. The solution utilizes a two loop QFT feedback structure. The inner loop structure stabilizes the motor's angular velocity and decreases the outer loop's uncertainty. The outer loop structure controls the RAM piston's position to …

Advanced Formation Flight Control, Michael J. Veth

Theses and Dissertations

In this thesis, the formation flight control problem is continued from four previous theses. Automatic formation flight involves controlling multiple aircraft equipped with standard Mach-hold, altitude hold, and heading-hold autopilots to maintain a desired distance from a lead aircraft or "rabbit". Changes in the rabbit's states are treated as disturbances to the system and rejected. Previous research is advanced in the following areas: Higher-order aircraft-autopilot models are included into the design and a new feedback control law is employed, resulting in more accurate simulations. An energy tracking scheme is developed and is shown to reduce wing aircraft energy excursions. Finally, …

Reduction Of Off-Boresight Fields For A Tem Horn Antenna, Dennis J. Wolstenholme

Theses and Dissertations

This research involves the design, modeling, and testing of both tapered periodic surfaces (TPS) and transverse electromagnetic (TEM) horns. The goal is to reduce the off-boresight fields for a TEM horn and increase the peak-to-peak field levels on boresight. This is accomplished by applying a TPS to the free space end. Two tapers are designed - one that approximates an exponential impedance function and one that approximates a triangular impedance function. Both reduce the off-boresight fields of the TEM horn. In most cases the exponential taper reduces the field levels further than the triangular taper. This research shows that a …

Improving The Performance Of Spiral Antennas By Using Passive Scatterers, Joseph S. Zaren

Theses and Dissertations

The purpose of this study was to explore the viability of improving the performance of cavity-backed antennas. Traditionally antenna cavities are filled with electromagnetic absorber to mitigate interference effects that would otherwise cause the antenna radiation pattern to vary widely at different frequencies. The approach used in this research was to replace the absorber with dielectric slabs, some of which contained arrays of dipoles. These dipole arrays were modeled as frequency selective surfaces using two periodic moment method based - computer programs and one transmission line program. A systematic study was performed that identified the effect of changing the dipole …

Flow Visualization Of A Turbulent Shear Flow Using An Optical Wavefront Sensor, Daniel W. Jewell

Theses and Dissertations

The research reported here investigated the use of a shearing interferometer (SI) wavefront sensor to determine the effects of shear-layer turbulence on an optical wavefront. A collimated helium-neon laser beam was propagated through a plane shear-layer produced by mixing helium and nitrogen at different velocities. Since the gases have different indices of refraction, the optical wavefront was distorted by different amounts by each gas. The SI measured the wavefront slope across the sampled area of the wavefront. The shear-layer was viewed from two orthogonal directions. This document contains shadow graphs, interference patterns imaged by each of the SI's six cameras, …

Image Perception Wavelet Simulation And Enhancement For The Visually Impaired, Lemuel Ray Myers Jr.

Theses and Dissertations

This research delves into the area of image enhancement for the visually impaired. Binocular macular degeneration a visual impairment, affects many Americans; since this condition could not be corrected with conventional glasses the literature suggested using an enhancement system which used a pre-emphasis algorithm to enhance the input image for output to the observer. The work of Dr. Eli Peli, a pioneer in the field of image enhancement, is examine and reproduced. Since his work concentrated mainly on frequency analysis of images, the bulk of this research involves using discrete wavelet analysis to augment that work. A biorthogonal wavelet set …

The Enhanced Performance Of An Integrated Navigation System In A Highly Dynamic Environment, Brian J. Bohenek

Theses and Dissertations

For the U.S. Air Force to maintain an accurate and reliable Navigation Reference System (NRS) with Carrier-Phase Global Positioning System (CPGPS) measurements, it must develop an accurate and robust NRS in the face of cycle slips caused by highly dynamic maneuvers. This research investigates the implementation of a double differencing between receivers-satellites scheme to improve the accuracy of current NRS models. The removal of the 'perfect Doppler velocity aiding measurements' (a very poor assumption of past research) was completed with stable and accurate results. The double differencing implemented showed improvement in the accuracy of the NRS. An investigation of two …

Characterization And Redesign Of The Afit Multielectrode Array, Richard G. Darenberg Jr.

Theses and Dissertations

Since 1978, faculty and graduate students from the Air Force Institute of Technology (AFIT) have been working on an implantable circuit array that can record visual signals from the brain or stimulate the brain. In the current design the circuit is a 16 x 16 array of pads, each pad being 160 x 160 micrometers with 250 micrometers spacing with an 'L' shaped reference pad used as a ground reference. The array is multiplexed so that only one I-O line is required to access all 256 pads. This research was twofold: first to analyze the existing circuit and identify sources …

Survey And Implementation Of Commercial Manual Controllers For A Generic Telerobotics Architecture, Thomas E. Deeter

Theses and Dissertations

The purpose of this study is to determine an input device for the Air Force's generic telerobotics architecture for large aircraft maintenance and repair. One area of concern is the human to machine interface, more specifically, which manual controller should be used for the specified tasks in this architecture. We mailed a survey to 68 companies in order to compile a list of possible input devices that the telerobotics architecture could use. 32 companies responded which gave me enough data to generate a list that described the physical traits of the input devices. We then divided the required tasks into …

A 3-D Finite Difference Time Domain Investigation Of Microwave Propagation Through Inhomogeneous Biological Materials, David B. Dunn Jr.

Theses and Dissertations

This paper extends past analysis of an optimal source distribution around a homogeneous sphere of muscle tissue by using a 3-D finite difference time domain (FDTD) scenario in which an anatomically correct human head model is irradiated. It first duplicates the analytical solution within an FDTD space using an FDTD computer code developed at Penn State University. This duplication uses a 9.45 cm radius sphere represented in an FDTD space of 2.35 mm cubic cells. FDTD simulations are then performed on four, three, and two layer laminated spheres, designed to provide simple models of a head. Finally, four simulations were …

Classification Of Ultra High Range Resolution Radar Using Decision Boundary Analysis, Christopher L. Eisenbies

Theses and Dissertations

This thesis examines the discrimination of targets with Ultra High Range Resolution (UHRR) radar data. Using these measured signals from frontal aspect angles of four aircraft classes, the baseline performance of the Adaptive Gaussian Classifier (AGC) is tested with respect to aligning exemplars to templates. Alignment plays a crucial role in the AGC's classification performance which can degrade by 11% for a target class. The AGC is compared to non-parametric classifiers, but no statistically significant degradation of performance is found. Data separability is analyzed by hounding the Bayes error. The data is well separated in a statistical sense. A feature …

The Design And Analysis Of Integrated Navigation Systems Using Real Ins And Gps Data, Curtis D. Evans

Theses and Dissertations

An extended Kalman filter (EKF) is used to combine the information obtained from a Global Positioning System (GPS) receiver and an Inertial Navigation System (INS) to provide a navigation solution. This research compares the results of an actual tightly-coupled GPS-INS integrated system with those obtained in computer simulation. Differences between the simulation and actual hardware results, such as navigation solutions and tuning values, are shown in the research. An analysis of various GPS models was studied to determine the best representation for a system truth model. Measurement updates and their effects upon position accuracies was considered and preliminary research was …

Analysis And Simulation Of Narrowband Gps Jamming Using Digital Excision Temporal Filtering, Gerald L. Falen

Theses and Dissertations

The purpose of this thesis is to investigate the performance of the Digital Excision Temporal Filter (DETF) to reject narrowband jammers used against the Global Positioning System (GPS). The DETF takes the Fast Fourier Transform (FFT) of the GPS signal and excises any FFT bins that are above a preselected threshold level. Then the excised signal is Inverse Fourier Transformed and fed to the GPS receiver. Several jammer types are simulated including Continuous Wave (CW), Pulse CW, Swept CW, Narrowband Spot Noise, and Wideband Barrage Noise jammers. Cases are also simulated using all but the Wideband Barrage Noise jammer at …

Embedology And Neural Estimation For Time Series Prediction, Robert E. Garza

Theses and Dissertations

Time series prediction has widespread application, ranging from predicting the stock market to trying to predict future locations of scud missiles. Recent work by Sauer and Casdagli has developed into the embedology theorem, which sets forth the procedures for state space manipulation and reconstruction for time series prediction. This includes embedding the time series into a higher dimensional space in order to form an attractor, a structure defined by the embedded vectors. Embedology is combined with neural technologies in an effort to create a more accurate prediction algorithm. These algorithms consist of embedology, neural networks, Euclidean space nearest neighbors, and …

Distributed Interactive Simulation Virtual Cassette Recorder (Dis Vcr): A Datalogger With Variable Speed Replay, Jonathan L. Fortner

Theses and Dissertations

The overall objective of the Distributed Interactive Simulation Virtual Cassette Recorder (DIS VCR) is to add a flexible replay capability to any DIS environment and specifically to the Remote Debriefing Tool (RDT). The DIS VCR's abilities include selective filtering of incoming DIS Protocol Data Units (PDUs), variable-speed replays, ability to pause, fast-forward, rewind, efficient data storage and retrieval, and an interface that simplifies the execution of those functions. The thesis includes a DIS VCR-compatible design for concurrent replay of audio extracted from signal PDUs and an extension to the replay design that supports unmodifiable rendering or receiving applications. For variable-speed …

Isolated Digit Recognition Without Time Alignment, Jeffrey M. Gay

Theses and Dissertations

This thesis examines methods for isolated digit recognition without using time alignment. Resource requirements for isolated word recognizers that use time alignment can become prohibitively large as the vocabulary to be classified grows. Thus, methods capable of achieving recognition rates comparable to those obtained with current methods using these techniques are needed. The goals of this research are to find feature sets for speech recognition that perform well without using time alignment, and to identify classifiers that provide good performance with these features. Using the digits from the TI46 database, baseline speaker-independent recognition rates of 95.2% for the complete speaker …

An Integrated Gps-Ins-Baro And Radar Altimeter System For Aircraft Precision Approach Landings, Robert A. Gray

Theses and Dissertations

Currently, the Department of Defense (DoD) and the commercial airline industry are utilizing the Instrument Landing System (ILS) during aircraft landings for precision approaches. The replacement system for the aging ILS was thought to he the Microwave Landing System (MLS). Instead, use of the Global Positioning System (GPS) is now thought to be a viable replacement for ILS precision approaches. The majority of current precision landing research has exploited 'stand-alone' GPS receiver techniques. This thesis instead explores the possibilities of using an extended Kalman filter (EKF) that integrates an Inertial Navigation System (INS), GPS, Barometric Altimeter, Pseudolite and Radar Altimeter …

Implementation And Demonstration Of A Multiple Model Adaptive Estimation Failure Detection System For The F-16, Peter K. Eide

Theses and Dissertations

A Multiple Model Adaptive Estimation (MMAE) algorithm is implemented with the fully nonlinear six-degree-of-motion, Simulation Rapid-Prototyping Facility (SRF) VISTA F-16 software simulation tool. The algorithm is demonstrated to be capable of identifying flight critical aircraft actuator and sensor failures at a low dynamic pressure (20,000 ft, .4 Mach). Research included single and dual complete failures. Tuning methods for accommodating model mismatch, including addition of discrete dynamics pseudonoise and continuous measurement pseudonoise, are discussed and demonstrated. Scalar residuals within each filter are also examined and characterized for possible use as an additional failure declaration voter. Robustness to sensor failures provided by …

Erp Analysis Using Matched Filtering And Wavelet Transform, Xueming Lin

Dissertations and Theses

Event related potentials (ERP's) carry very important information that relates to the performance of the brain functions of the human being. Further studies have identified that one component, in particular, P₃₀₀, is affected by the memory process. Matched filter is used to improved the SNR of signal ERP's. We use the output of the matched filter to distinguish the difference of the waveforms between normal subjects and memory-impaired subjects. In our study, we found that the peak values of the matched filtering output were different between normal subjects and memoryimpaired subjects. Also, as an application, wavelet transform is …

Algorithms In Fault-Tolerant Clos Networks, Hyunyeop Lee

Dissertations

No abstract provided.

Cebus Demonstration System, Liang-Chuang Chen

Theses

A CEBus demonstration system is constructed and applied to aspects of home automation security. Two M68HC16Z1 evaluation boards are used as CEBus nodes. Two CEBus spread spectrum power line modems (SSC PLCEMS) interconnect the nodes. An SSC PLCEMS handles all spread spectrum signal generation and reception.

The application programs in the two boards are written in assembly language based upon CAL (Common Application Language), a CEBus standard.

The standard CEBus frame format and FCS (Frame Check Sequence) are implemented by software in the Data Link Layer. Encoding and decoding binary information into UST format are implemented in the Physical Layer. …

A Distributed Network Architecture For Video-On-Demand, Ge Dai

Theses

The objective of this thesis is to design a distributed network architecture that provides video - on - demand services to public subscribers. This architecture is proposed as an alternative to a centralized video service system. The latter system is currently being developed by Oracle Corporation and NCube Corporation.

A simulator is developed to compare the performance of both the distributed and centralized video server architectures. Moreover, an estimate of the cost of both systems is derived using current price data.

It is shown that the distributed video server architecture offers a better cost / performance trade-off than the centralized …

Artificial Dielectrics : Characteristics At Low And Microwave Frequencies, Nitish Agrawal

Theses

Artificial Dielectrics have been characterized using transmission line and s- parameter measurements. The complex dielectric constant and loss of graphite filled and non-poled piezoelectric-aggregate (Polyvinylidene Fluoride, PVDF) filled plastic (PMMA) has been characterized at low (1kHz-10kHz range, i.e., the VLF, very low frequency, range) and microwave frequencies. The average diameter diameter of graphite particles used was thirty microns. Measurements were performed on very fine graphite (one micron diameter grains) and 30 micron sized grains for comparison purposes. Fine grain graphite particles exhibited a, larger real dielectric constant, probably owing to a larger dipole effect. The dielectric constant characterization has also …