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Full-Text Articles in Engineering

Rule-Based Frequency Domain Speech Coding, Vance M. Mcmillan Dec 1990

Rule-Based Frequency Domain Speech Coding, Vance M. Mcmillan

Theses and Dissertations

A speech processing system is designed to simulate the transmission of speech signals using a speech coding scheme. The transmitter portion of the simulation extracts a minimized set of frequencies in Fourier space which represents the essence of each of the speech timeslices. These parameters are then adaptively quantized and transmitted to a receiver portion of the coding scheme. The receiver then generates an estimate of the original timeslice from the transmitted parameters using a sinusoidal speech model. After initial design, the thesis investigates how each of the design parameters affect the human perceived quality of speech. This is done …

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Characterization Of Radar Signals Using Neural Networks, Daniel R. Zahirniak Dec 1990

Characterization Of Radar Signals Using Neural Networks, Daniel R. Zahirniak

Theses and Dissertations

Recent work concerning artificial neural networks has focused on decreasing network training times. Kernel Classifier networks, using radial basis functions (RBFs) as the kernel function, can be trained quickly with little performance degradation. Short training times are critical for systems which must adapt to changing environments. The function of Kernel Classifier networks is based on the principle that multivariate functions can be approximated via linear combinations of RBFs. RBFs can also perform probability density estimations, making classifications approximating a Baye's optimal descriminant. Methods used to set the RBF centers included matching the training data, Kohonen Training, K-Means Clustering and placement …

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Model-Based Reasoning In Electronic Repair, Kenneth B. Cohen Dec 1990

Model-Based Reasoning In Electronic Repair, Kenneth B. Cohen

Theses and Dissertations

Diagnosis is the process of identifying the cause for an observed behavior of a system. Model-based reasoning uses knowledge of the behavior of the component and the interconnection of the components to diagnose a system. This thesis investigates the application of model-based reasoning to the problem of isolating faulty components of an analog electronic circuit. More specifically, this thesis describes an architecture for a model-based diagnostic system for electronic modules, implements an assumption-based truth maintenance system (one of the component parts of a model-based diagnostic system), and creates the interface between the truth maintenance system and the diagnostic system.

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Implementation Of The Modified Monte Carlo Technique Using Importance Sampling On The Block Oriented System Simulator, John B. Bennett Dec 1990

Implementation Of The Modified Monte Carlo Technique Using Importance Sampling On The Block Oriented System Simulator, John B. Bennett

Theses and Dissertations

The purpose of this thesis was to implement the Modified Monte Carlo technique using Importance Sampling on the Block Oriented System Simulator (BOSS). Computer simulation techniques of communications systems were reviewed. Next, conventional Monte Carlo techniques and Modified Monte Carlo techniques using Importance Sampling were reviewed. Models of Binary Phase Shift Keying (BPSK) systems using both Monte Carlo techniques were implemented and simulated. Reasons for the model using Importance Sampling not working correctly are postulated. The Monte Carlo technique is a method of ensuring the an inherently infinite procedure, such as determining system bit error rate (BER), can be determined …

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Network Reduction Using Error Prediction, Michael V. Gilsdorf Dec 1990

Network Reduction Using Error Prediction, Michael V. Gilsdorf

Theses and Dissertations

This thesis investigates gradient descent learning algorithms for multi-layer feed forward neural networks. A technique is developed which uses error prediction to reduce the number of weights/nodes in a network. The research begins by studying the first and second order back-prop training algorithms along with their convergence properties. A network is reduced by making an estimate of the amount of error which would occur when a weight(s) is removed. This error estimate is then used to determine if a particular weight is essential to the operation of the network. If not, it is removed and the network retrained. The process …

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Silicon Hybrid Wafer Scale Integration (Wsi) Used To Fabricate A Hilbert Transform Integrated Circuit Module, Daniel J. Gaughan Dec 1990

Silicon Hybrid Wafer Scale Integration (Wsi) Used To Fabricate A Hilbert Transform Integrated Circuit Module, Daniel J. Gaughan

Theses and Dissertations

This research was performed in order to develop a superior processing schedule for fabricating Wafer-Scale Integration (WSI) circuit modules. This technology allows the design of circuitry that spans the entire surface of a silicon substrate wafer. The circuit element employed in this research was the Hilbert transform, a digital phase-shifting circuit. The transform was incorporated into a three Integrated Circuit (IC) die package that consisted of a mechanically supportive silicon wafer, three IC die, and a planarizing silicon wafer. The die were epoxied into this wafer using a Teflon block as a flat, and the combination was epoxied onto the …

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A Study Of The Effects Of Noise Jamming On Radar Receivers, Paul E. Bishop Dec 1990

A Study Of The Effects Of Noise Jamming On Radar Receivers, Paul E. Bishop

Theses and Dissertations

A comprehensive study of the effects of noise jamming on various pulsed radar receiver types is proposed. First, a literature review on the sources of electrical noise and various jamming waveforms is presented. The power spectra for three noise jamming waveforms are rigorously derived. These cases are shot noise in a parallel-plate diode, a series of pulses with random amplitudes and intervals, and for a series of pulses with random amplitudes, spacing and phases. Next, the probability density functions for the output of linear and quadratic detectors are developed. For each detector type, the probability density functions for the cases …

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Brightness Invariant Port Recognition For Robotic Aircraft Refueling, Richard A. Bennett Dec 1990

Brightness Invariant Port Recognition For Robotic Aircraft Refueling, Richard A. Bennett

Theses and Dissertations

The purpose of this thesis effort was to develop and test a brightness invariant recognition algorithm that would locate and identify the half-scale mock up of a Universal Aerial Refueling Receptacle Slipway Installation (UARRSI) aerial refueling port in different lightening conditions. This was accomplished by developing a brightness invariant port recognition of identifiable attributes of the refueling port to locate and identify the UARRSI port. Based on this approach, a brightness invariant port recognition system (BIPRS) was demonstrated which identified the refueling receptacle in different lightening conditions. The BIPRS was also invariant to orientation and size of the UARRSI port. …

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Interference Cancellation In Rf Signals Using Adaptive Array Techniques, Mark E. Brown Dec 1990

Interference Cancellation In Rf Signals Using Adaptive Array Techniques, Mark E. Brown

Theses and Dissertations

This study investigated the effectiveness of the Least Means Squared (LMS) algorithm against various types of common jammers. The LMS algorithm was implemented using the Block Oriented Systems Simulator (BOSS). The LMS algorithm was inserted at the output of a two element antenna array. The array was configured so as to have one-half wavelength spacing. A quadrature hybrid signal structure was used. The array was then tested against a barrage and sweep jammer. The barrage jammer testing consisted of varying each of the three available jammer parameters; power, frequency and angle of arrival individually. The sweep jammer testing consisted of …

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Evaluation Of An Interdigitated Gate Electrode Field-Effect Transistor For Detecting Organophosphorus Compounds, Charles P. Brothers Jr. Dec 1990

Evaluation Of An Interdigitated Gate Electrode Field-Effect Transistor For Detecting Organophosphorus Compounds, Charles P. Brothers Jr.

Theses and Dissertations

This study used integrated circuit microsensors to detect organophosphorus compounds. Chemically-sensitive thin films, copper phthalocyanine, DFPase, succinyl chloride, succinylcholine chloride, 2- naphthol(B), and L-histidine dihydrochloride,were deposited on interdigitated gate electrode (IGE) structures, with an average thickness of 2000A. Thin film electrical performance characteristics were measured for several parameters, including: DC resistance, AC impedance, time-domain, and spectral responses from 10 Hz to 1 MHz. Each microsensor contained nine IGEs; each IGE possessed an in situ field-effect transistor amplifier. After purging each sensor with filtered air, it was exposed to one or two of the following gases: diisopropyl fluorophosphate (DFP), diisopropyl methylphosphonate, …

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Angle Of Arrival Detection Through Artificial Neural Network Analysis Of Optical Fiber Intensity Patterns, Scott Thomas Dec 1990

Angle Of Arrival Detection Through Artificial Neural Network Analysis Of Optical Fiber Intensity Patterns, Scott Thomas

Theses and Dissertations

The optical sensors of United States Air Force reconnaissance vehicles, such as satellites, are subject to temporary or permanent blinding from hostile (or threat) laser radiation. By detecting and determining the angle of arrival (AOA) of the hostile radiation, the reconnaissance vehicle may be able to protect its optical sensors by taking evasive maneuvers or by shutting down the optical sensor (such as closing a shutter) until the threat has passed. In addition, the vehicle can relay information to its ground terminal allowing the intelligence community to determine the source of the hostile laser radiation. This thesis demonstrated that an …

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Predicting The Performance Of Airborne Antennas In The Microwave Regime, David P. Carroll Dec 1990

Predicting The Performance Of Airborne Antennas In The Microwave Regime, David P. Carroll

Theses and Dissertations

This study investigated the application of a high-frequency model (Uniform Geometrical Theory of Diffraction) of electromagnetic sources mounted on a curved surface of a complex structure. In particular, the purpose of the study was to determine if the model could be used to predict the radiation patterns of cavity-backed spiral antennas mounted on aircraft fuselages so that the optimum locations for the antennas could be chosen during the aircraft design phase. A review of literature revealed a good deal of work in modeling communications, navigation, identification antennas (blade monopoles and aperture slots) mounted on a wide variety of aircraft fuselages …

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Classification Of Correlation Signatures Of Spread Spectrum Signals Using Neural Networks, Richard A. Chapman Dec 1990

Classification Of Correlation Signatures Of Spread Spectrum Signals Using Neural Networks, Richard A. Chapman

Theses and Dissertations

The major goals of this thesis were to determine if Artificial Neural Networks (ANNs) could be trained to classify the correlation signatures of two classes of spread spectrum signals and four classes of spread spectrum signals. Also, the possibility of training an ANN to classify features of the signatures other than signal class was investigated. Radial Basis Function Networks and Back-Propagation Networks were used for the classification problems. Correlation signatures of four types or classes were obtained from United States Army Harry Diamond Laboratories. The four types are as follows: direct sequence (DS), linearly-stepped frequency hopped (LSFH), randomly-driven frequency hopped …

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Feasibility Analysis Of Developing A Formal Performance Model Of Ada Tasking, Kathryn J. Edwards Dec 1990

Feasibility Analysis Of Developing A Formal Performance Model Of Ada Tasking, Kathryn J. Edwards

Theses and Dissertations

As software system requirements become more complex, software engineers must carefully design the systems to ensure the systems to ensure the systems adequately meet all requirements, both functional and non-functional. Because real-time systems have timing constraints, in addition to the more traditional behavioral constraints, a comprehensive software design analysis model is required which incorporate performance, timing, and behavioral constraints. Although the Ada language tasking constructs are compiler independent, Ada tasking is dependent on its runtime environment; therefore, a formal model of Ada tasking and its associated runtime environment is important in order for system designers to make realistic decisions when …

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Numerical Approximations Of The Green's Functions For A Theoretical Model Of An Aperture Fed Stacked-Patch Microstrip Antenna, Ronald E. Erwert Dec 1990

Numerical Approximations Of The Green's Functions For A Theoretical Model Of An Aperture Fed Stacked-Patch Microstrip Antenna, Ronald E. Erwert

Theses and Dissertations

The numerical approximations of the Green's functions for a theoretical model of an aperture fed stacked patch microstrip antenna are presented. The Green's functions approximated are those developed by Nazar (AFIT Thesis GE-89D-37), Green's Functions for a Theoretical Model of an Aperture Fed Stacked-Patch Microstrip Antenna. Each complex valued Green's function was written as a function of the source-observer separation. The behavior of each Green's function was analyzed, and it was found that they could all be approximated by three separate functions. The approximating functions were either polynomials or rational functions composed of polynomials. One component could be approximated by …

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A Method Of Moments Solution For The Electric Currents On An Aperture-Fed, Stacked Patch Microstrip Antenna, William L. Irvin Dec 1990

A Method Of Moments Solution For The Electric Currents On An Aperture-Fed, Stacked Patch Microstrip Antenna, William L. Irvin

Theses and Dissertations

This study presents a method of moments solution for the surface currents and charge distributions on an aperture-fed, stacked patch antenna. To make the solution independent of the antenna excitation technique, an aperture magnetic current distribution is assumed, and the spatial Green's functions of the antenna are used to calculate the tangential fields on the antenna patches and coefficients for a finite series expression of the surface currents and charge densities. The Green's functions of the antenna are modeled with polynomials that are a function of the radial distance separating observer and source locations. The method of moments solution is …

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Gabor Filters And Neural Networks For Segmentation Of Synthetic Aperture Radar Imagery, Albert P. L'Homme Dec 1990

Gabor Filters And Neural Networks For Segmentation Of Synthetic Aperture Radar Imagery, Albert P. L'Homme

Theses and Dissertations

This research investigates Gabor filters and artificial networks for autonomous segmentation of 1 foot by 1 foot) high resolution polarimetric synthetic aperture radar (SAR). Processing involved frequency correlation between the SAR imagery and biologically motivated Gabor functions. Methods for selecting the Gabor tuning parameters from the endless choices of frequency, rotation, standard deviation and bandwidth are discussed. Using these parameters, resulting Gabor correlation images were reduced in speckle, and more detailed. This research used cosine Gabor functions and operated on single polarization HH magnitude data. Following selection of the appropriate Gabor features, multiple Gabor representations were generated and converted for …

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Analysis And Testing Of A Bistatic Radar Cross Section Measurement Capability For The Afit Anechoic Chamber, Timothy D. Mccool Dec 1990

Analysis And Testing Of A Bistatic Radar Cross Section Measurement Capability For The Afit Anechoic Chamber, Timothy D. Mccool

Theses and Dissertations

This research effort examined the feasibility of performing bistatic radar cross section (RCS) measurements in the AFIT anechoic chamber. The capability was established to measure the bistatic RCS of a target versus frequency and versus target azimuth angle. In either case, one of three bistatic angles (angle between transmit and receive antennas) is available: 45 degrees, 90 degrees, and 135 degrees. Accurate bistatic RCS measurements were obtained using a CW radar and utilizing background subtraction, bistatic calibration, and software range gating. Simple targets were selected for validation purposes since their bistatic RCS could be predicted. These consisted of spheres and …

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Analysis Of Visual Illusions Using Gabor Filters, Richard A. Oberndorf Dec 1990

Analysis Of Visual Illusions Using Gabor Filters, Richard A. Oberndorf

Theses and Dissertations

This thesis has demonstrated the correctness of using spatial filters in the analysis of various visual illusions; the specific form of filter has been derived from a Gabor equation model of simple cell response on the visual cortex. The Gabor Low Pass Filter (GLPF) applied to these anomalies was derived from proposals made that simple cell response on the visual cortex may be modeled by a set of equations originally proposed by Gabor in the 1940's. Based upon the extension of these equations into two dimensions, a GLPF process was applied to computer-generated black and white illusions (the Kanizsa Triangle, …

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Quantization Noise Characteristics Resulting From Gaussian, Negative- Exponential, And Sinusoidal Random Input Signals, Van N. Osborne Dec 1990

Quantization Noise Characteristics Resulting From Gaussian, Negative- Exponential, And Sinusoidal Random Input Signals, Van N. Osborne

Theses and Dissertations

The purpose of this study was to investigate the trade-off between the number of quantization levels and the resulting noise characteristics for three classes of commonly occurring input signals, namely, those signals possessing Gaussian, negative-exponential and random sinusoidal distributions. This study derived expressions for the mean-squared error, output spectrum and error spectrum by expanding the nonlinear quantization function into a summation of orthogonal polynomials matched to the corresponding input signal distribution. Once accomplished, orthogonality properties were applied to provide usable expressions. A set of three Fortran 77 programs were developed- each of which applied to one of the studied input …

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Digital Control Of The Utah/Mit Dexterous Hand: Initial Evaluation And Analysis, Lloyd W. Rainey Iii Dec 1990

Digital Control Of The Utah/Mit Dexterous Hand: Initial Evaluation And Analysis, Lloyd W. Rainey Iii

Theses and Dissertations

An experimental digital platform is developed as an environment on which to evaluate digital control strategies for dexterous manipulation with a pneumatically actuated tendon-driven manipulator. This environment is used to begin the study of advanced control methods that are suitable for providing the tracking accuracy required for grasping and dexterous manipulation with a pneumatically actuated tendon-driven end-effector. The digital platform consists of a PC/AT-386 and a single board MC68020 microcomputer in a VME chassis with shared RAM between the two processors to control the Utah/MIT Dexterous Hand (UMDH). The MC68020 controls the A/D and D/A access for the UMDH, while …

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Moving-Bank Multiple Model Adaptive Estimation And Control Applied To A Large Flexible Space Structure, Robert B. Moyle Dec 1990

Moving-Bank Multiple Model Adaptive Estimation And Control Applied To A Large Flexible Space Structure, Robert B. Moyle

Theses and Dissertations

The performance of moving-bank multiple model adaptive estimation (MMAE) and control (MMAC) algorithms for large space structure control is analyzed in this thesis. The performance of a six-state filter model and associated controller are evaluated on the basis of estimation/control performance against a 24-estate truth model. A model developed using finite element analysis is used to approximate a large flexible space structure. The space structure is configured as a two-bay truss which is attached to a large central hub, where the mass of the hub is considered to be much more larger than the mass of the flexible structure. The …

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The Radar Range Equation For The Detection Of Steady Targets In Weibull Clutter, Leon C. Rountree Dec 1990

The Radar Range Equation For The Detection Of Steady Targets In Weibull Clutter, Leon C. Rountree

Theses and Dissertations

In this thesis, the detection characteristics of a steady target immersed in radar clutter characterized by returns statistically modeled according to a Weibull probability density function are developed. A detector model is developed by modifying an envelope detection scheme used to detect deterministic signals in Gaussian noise. By examining the statistics of the detector output under alternate hypotheses, an expression for the probability of detection (P sub d) is developed in terms of the probability of false alarm (P sub fa), the signal-to-clutter ratio (SCR), and the Weibull skewness parameter (b), which is a function of the type of terrain …

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Establishment Of A Fabrication And Measurement Capability For Aperture-Fed Stacked Patch Microstrip Antennas At The Air Force Institute Of Technology, Christopher I. Terry Dec 1990

Establishment Of A Fabrication And Measurement Capability For Aperture-Fed Stacked Patch Microstrip Antennas At The Air Force Institute Of Technology, Christopher I. Terry

Theses and Dissertations

Much time and effort has been applied to accurately model aperture- fed stacked patch microstrip antennas at the Air Force Institute of Technology (AFIT). The results of this study provide AFIT with the capability to fabricate and measure these antennas for comparison of measured radiation characteristics to the predicted characteristics. Basic microstrip patch antenna theory is reviewed, as well as the motivation leading to the development of aperture-fed stacked patch microstrip antennas. The fabrication process used to produce the two antennas manufactured for this study is described in detail. The construction of a small anechoic chamber for pattern measurements is …

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Pulsed Compression For Aerosol Ranging With Coherent Pulse-Doppler Lidar Systems, Jerry L. Rogers Dec 1990

Pulsed Compression For Aerosol Ranging With Coherent Pulse-Doppler Lidar Systems, Jerry L. Rogers

Theses and Dissertations

This thesis provides a thorough review of conventional matched filter radar theory as it applies to aerosol sensing lidar. Basic matched-filter radar theory and the complex, dense aerosol target model eventually lead to a general derivation of the matched-filter radar receiver response to a dense aerosol target environment. The matched-filter response is obtained in terms of a two dimensional convolution of the target scattering function and the radar ambiguity function. The range and radial velocity resolution of various radar signals were compared using the matched-filter radar receiver and scattering function models. Pulse compression radar signals were compared to the simple …

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Te Scattering From A Dielectric Coated Conducting Strip, William D. Wood Jr. Dec 1990

Te Scattering From A Dielectric Coated Conducting Strip, William D. Wood Jr.

Theses and Dissertations

Consider a plane wave incident on a conducting strip of infinite length coated on one side with a thin, uniform coating of lossless dielectric, and let the incident magnetic field vector be parallel to the edges of the strip. From first principles we develop the integral equations relating the total, incident, and scattered fields in the dielectric. We expand the fields in the dielectric slab as the sum of three plane waves (the 'forced' wave and two oppositely-directed surface waves). The phase constants in the x and y directions are known and the wave amplitudes are found using least-squared- error-point-matching. …

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An Evaluation Of An Ada Implementation Of The Rete Algorithm For Embedded Flight Processors, F. Jesse Fanning Dec 1990

An Evaluation Of An Ada Implementation Of The Rete Algorithm For Embedded Flight Processors, F. Jesse Fanning

Theses and Dissertations

The purpose of this thesis was to design and develop an expert system shell in Ada, and to evaluate the shell's execution and size performance to determine its suitability for real-time operation on the MIL-STD-1750A embedded flight processor. The expert system shell uses the CLIPS/Ada inference engine, a forward-chaining Ada implementation of Rete. The expert system shell design is presented along with an overview of the target environment--the MIL-STD-1750A VHSIC Avionic Modular Processor (VAMP) running under the Ada Avionics Real-Time Software (AARTS) Operating System. Theoretical and empirical complexity analyses of the inference engine are presented and discussed in view of …

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Characterization Of Multilayer Perceptrons And Their Application To Multisensor Automatic Target Detection, Dennis W. Ruck Dec 1990

Characterization Of Multilayer Perceptrons And Their Application To Multisensor Automatic Target Detection, Dennis W. Ruck

Theses and Dissertations

The multilayer perceptron was extensively analyzed. A technique for analyzing the multilayer perceptron, the saliency measure, was developed which provides a measure of the importance of inputs. The method was compared to the conventional statistical technique of best features and shown to provide similar rankings of the input. Using the saliency measure, it is shown that the multilayer perceptron effectively ignores useless inputs and that whether it is trained using backpropagation or extended Kalman filtering, the weighting of the inputs is the same. The backpropagation training algorithm is shown to be a degenerate version of the extended Kalman filter. The …

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Estimation Of Evoked Fields Using A Time-Sequenced Adaptive Filter With The Modified P-Vector Algorithm, Jeffery A. Kepley Dec 1990

Estimation Of Evoked Fields Using A Time-Sequenced Adaptive Filter With The Modified P-Vector Algorithm, Jeffery A. Kepley

Theses and Dissertations

This thesis describes a time sequenced adaptive filter developed to estimate visually evoked fields (EF) using visually evoked potentials (EP). These non-stationary signals are buried in strong background noise. The two types of noise are magnetoencephalogram (MEG) and electronencephalogram (EEG). The filter implementation is based on the Ferrara Time Sequenced Adaptive (TSAF) using the Least-Mean-Square (LMS) algorithm and the Williams modified P-vector algorithm (mPa). This essentially results in two filters. A two stage filter structure is used in which the first stage removes the time-varying mean of the input signals. This allows the second stage to process zero-mean signals which …

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Photo-Induced Electrochemical Etching Of Inp Semiconductor In A Thin Film Cell, Bungsu Iskandar Oct 1990

Photo-Induced Electrochemical Etching Of Inp Semiconductor In A Thin Film Cell, Bungsu Iskandar

Theses

The Photo-Induced Electrochemical Etching of n-InP wafer in aqueous solution is investigated for both reservoir and capillary systems. A sinusoidal spatial variation of light intensity pattern is directly illuminated and promoting etching on an InP semiconductor wafer. The etching process is time-efficient, and produces highly isotropical and a promising high resolution pattern. It gives a good reproducibility and has less contaminating features. Its features may be explained by a non-linear relationship between the electrolyte concentration and the photo-generated holes density at the interaction surface. An optimal reaction rate is determined by the ratio of the reactivity to ionic diffusion, either …

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