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Air Force Institute of Technology

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Articles 271 - 300 of 349

Full-Text Articles in Electrical and Electronics

Phased Array Antenna Analysis Using Hybrid Finite Element Methods, Daniel T. Mcgrath Jun 1993

Phased Array Antenna Analysis Using Hybrid Finite Element Methods, Daniel T. Mcgrath

Theses and Dissertations

This research in computational electromagnetics developed a new method for predicting the near-field mutual coupling effects in phased array antennas, using the finite element method (FEM) in combination with integral equations. Accurate feed modeling is accomplished by enforcing continuity between the FEM solution and an arbitrary number of wave guide models across a ground plane aperture. A periodic integral equation is imposed above the antenna's physical structure in order to enforce the radiation condition and to confine the analysis to an array unit cell. The electric field is expanded in terms of vector finite elements, and Galerkin's method is used …

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Frequency Domain Speech Compression Using The Karhunen-Loeve Transform, Donald W. Dryley Mar 1993

Frequency Domain Speech Compression Using The Karhunen-Loeve Transform, Donald W. Dryley

Theses and Dissertations

The purpose of this study was test the influence of phase on the quality of speech reproduced by a speaker dependent compression system. The tests consisted of compressing frequency domain speech vectors using the Karhunen-Loeve Transform, with and without phase, then making subjective judgements as to the reproduced quality. Error Metrics were then tested for their suitability as predictors of reproduced quality. The compression software transformed each speech vector into a vector of complex Fourier coefficients (only half of the coefficients are needed as transform is hermitian). Phase was preserved by using the real frequency components to form one vector …

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Self-Referenced Speckle Holography (Srsh) Image Reconstruction Performance, John R. Devey Mar 1993

Self-Referenced Speckle Holography (Srsh) Image Reconstruction Performance, John R. Devey

Theses and Dissertations

The Speckle Holography technique uses a series of short exposure images and associated wave front sensor measurements to reconstruct astronomical images. The reconstruction technique effectively boosts the amplitude of high spatial frequencies to allow for finer resolution of astronomical objects. A simulation package that calculates the optical transfer function (OTF) of a telescopic system was previously developed for the Phillips Laboratory. This software was modified slightly to provide the Speckle Holography system transfer function (STF) for a telescopic system under varying seeing conditions.

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Real Image Visual Display System, James R. Brandt Dec 1992

Real Image Visual Display System, James R. Brandt

Theses and Dissertations

This thesis investigates a technique for improving the perception of three-dimensionality in images generated by a Silicon Graphics workstation. The technique involves using a spherical mirror into which the graphics from the CRT are projected. A real image of the graphic is formed by the mirror and it appears to be floating at the image plane. The three-dimensional effect is improved by adding reflections or shadows of the displayed object. Additionally, a method of using real objects with computer generated shadows and computer generated objects with real shadows is investigated. This is done in an effort to quantify how far …

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Theory And Implementation Of Wavelet Analyses In Rational Resolution Decompositions, Bruce P. Anderson Dec 1992

Theory And Implementation Of Wavelet Analyses In Rational Resolution Decompositions, Bruce P. Anderson

Theses and Dissertations

The multiresolution analysis (MRA) developed by Mallat and Meyer and further discussed by Daubechies is a useful tool in the analysis of sampled signals such as images and speech. This thesis develops the theory and implementation of a rational-resolution analysis (RRA) as an extension of the dyadic MRA for arbitrary rational dilation factors. We present a method to calculate families of compactly-supported scaling functions and wavelets based on arbitrary integer dilation factors and provide examples. The perfect- reconstruction properties of the RRA are discussed and it is demonstrated that the compactly-supported scaling functions and wavelets do not yield perfect- reconstruction. …

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Analysis And Simulation Of Modified Tanlock And Delay Lock Loops For Gps Receiver Design, James A. Hird Dec 1992

Analysis And Simulation Of Modified Tanlock And Delay Lock Loops For Gps Receiver Design, James A. Hird

Theses and Dissertations

The purpose of this thesis is to investigate two types of tracking loops used in Global Positioning System (GPS) receiver design. The first loop, the Delay Lock Loop (DLL), is a code tracking loop used to synchronize a locally generated pseudo-noise (PN) sequence with the PN sequence in the GPS satellite broadcast. Synchronization of the PN sequences is essential for de-spreading the direct-sequence spread spectrum (DS/SS) broadcast and demodulating the transmitted data. The second loop, the Modified Tanlock Loop (MTLL), is a carrier tracking loop used to synchronize the phase of a voltage controlled oscillator (VCO) with the carrier of …

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Automated Face Recognition System, Kenneth R. Runyon Dec 1992

Automated Face Recognition System, Kenneth R. Runyon

Theses and Dissertations

In this thesis three variations of an end-to-end face recognition prototype system are developed, implemented and tested. Each version includes real-time image collection, automated segmentation, preprocessing, feature extraction, and classification. The first version uses a Karhunen Loeve Transform (KLT) feature extractor and a K-nearest neighbor classifier. Version two uses the same feature set but utilizes a multilayer perception neural network with a back propagation learning rule. Finally the third version uses a Discrete Cosine Transform as the feature extractor and the K-nearest neighbor as the classifier. Only the KLT versions of the system were tested. The tests were based on …

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Kalman Filter Tracking Of A Ballistic Missile Using Forward Looking Infrared Measurements And Doppler Returns, Michael L. Ching Dec 1992

Kalman Filter Tracking Of A Ballistic Missile Using Forward Looking Infrared Measurements And Doppler Returns, Michael L. Ching

Theses and Dissertations

The Air Force Institute of Technology (AFIT) has been involved in developing Kalman Filter trackers for airborne targets for the last 14 years. The goal of this particular thesis was to track a ballistic missile in the boost phase at ranges up to 2000 km, in order to control a high energy laser weapon designed to destroy the target The filter developed combined an existing 'FLIR' filter, which estimated location of the plume intensity centroid based on measurements from a forward looking infrared sensor (FLIR), and an existing center-of-mass filter, which estimated the offset between the plume and missile center-of-mass …

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An Analytical And Experimental Investigation Of Fm-By-Noise Jamming, Charles J. Daly Dec 1992

An Analytical And Experimental Investigation Of Fm-By-Noise Jamming, Charles J. Daly

Theses and Dissertations

Among the jamming waveforms used in Electronic Warfare, FM-by-noise is the least understood, and no exhaustive analytical and experimental investigation of the subject exists. This investigation presents a thorough review, consolidation, and elucidation of the theory of FM-by-noise. To explain and predict the behavior of FM-by-noise at RF and IF, three useful ratios, namely the deviation-to-victim ratio, the noise-to-victim ratio, and the sweep- to-victim ratio, are developed. To complement the theory, results of FM-by-noise jamming experiments conducted using commercial test and measurement equipment are presented. Specifically, the time- and frequency-domain behavior of FM-by- noise at RF and IF is studied …

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Remote Sensing Of Turbulence And Transverse Atmospheric Wind Profiles Using Optical Reference Sources, Steven C. Koeffler Dec 1992

Remote Sensing Of Turbulence And Transverse Atmospheric Wind Profiles Using Optical Reference Sources, Steven C. Koeffler

Theses and Dissertations

This thesis examines a remote sensing technique for measuring the atmospheric structure constant and the transverse atmospheric wind velocity as a function of altitude by performing temporal and spatial correlations of band pass filtered wave front slope sensor measurements. Two point sources are used to illuminate two pairs-of cc>-located wave front slope sensors. The sources and sensors are arranged to give rise to crossed optical paths. For each pair of wave front slope sensors, the output of the larger sensor is subtracted from the output of the smaller sensor. This band pass filters the smaller sensor's output. The filtered …

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Optical Haar Wavelet Transforms Using Computer Generated Holography, Peter G. Block Dec 1992

Optical Haar Wavelet Transforms Using Computer Generated Holography, Peter G. Block

Theses and Dissertations

This research introduces an optical implementation of the continuous wavelet transform to filter images. The wavelet transform is modeled as a correlation process and is implemented with a Vander Lugt correlator. The orthonormal basis set used is composed of two one-dimensional Haar functions and a two-dimensional Haar function. Each wavelet, as well as its first two dyadic scalings, is implemented with computer generated holography. The Interferogram method, which represents a function only in terms of its phase, is used to encode the wavelet functions. The results are imaged onto a CCD array and captured using a framegrabber. The optical results …

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Cepstral And Auditory Model Features For Speaker Recognition, John M. Colombi Dec 1992

Cepstral And Auditory Model Features For Speaker Recognition, John M. Colombi

Theses and Dissertations

The TIMIT and KING databases, as well as a ten day AFIT speaker corpus, are used to compare proven spectral processing techniques to an auditory neural representation for speaker identification. The feature sets compared were Linear Predictive Coding (LPC) cepstral coefficients and auditory nerve firing rates using the Payton model. This auditory model provides for the mechanisms found in the human middle and inner auditory periphery as well as neural transduction. Clustering algorithms were used to generate speaker specific codebooks - one statistically based and the other a neural approach. These algorithms are the Linde-Buzo-Gray (LBG) algorithm and a Kohonen …

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Satcom General Purpose Modem Dscs Iii Sct Beacon Telemetry Display, James D. Coppola Dec 1992

Satcom General Purpose Modem Dscs Iii Sct Beacon Telemetry Display, James D. Coppola

Theses and Dissertations

This thesis documents the design and implementation of a DSCS III single Channel Transponder (SCT) beacon telemetry display. The system is a personal computer based design which interfaces to three SCT beacon receiver/demodulators. The software was designed to decode and display both the DSCS III A and DSCS HI B satellite beacons. Recordings of the SCT beacon display can be made on paper and/or magnetic media when triggered by the user, a watchdog timer, or the SCT command accept telemetry bit. In addition, the system can be configured with an IRIG B Universal Time Coordinates (UTC) card which enables the …

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Computer Simulation Of A General Purpose Satellite Modem, William L. Montgomery Jr. Dec 1992

Computer Simulation Of A General Purpose Satellite Modem, William L. Montgomery Jr.

Theses and Dissertations

The purpose of this research was to model and simulate the performance of a digital phase shift keyed satellite modem. The probability of bit error (P sub b) at different levels of energy per bit to noise power ratio (E sub b/N sub o) was the performance measure. The channel was assumed to contribute only additive white Gaussian noise. A second order Costas loop performs demodulation in the modem and was the key part of the simulation. The Costas loop with second order Butterworth arm filters was tested by finding the response to a phase or frequency step. The Costas …

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The Effect Of An Adaptive Optical System's Spatio-Temporal Response On Imaging Performance, Patrick M. Harrington Dec 1992

The Effect Of An Adaptive Optical System's Spatio-Temporal Response On Imaging Performance, Patrick M. Harrington

Theses and Dissertations

Ideally, an adaptive optical control system would have instantaneous temporal response and infinite spatial bandwidth. In real systems, the response time of the adaptive optical control system is limited by the integration time of the wave front sensor, the computational time of the control algorithm, and the actuator response time. Additionally, finite inter actuator spacing limits the deformable mirror's ability to reproduce spatial frequencies having a period less than twice this spacing. Although analyses general enough to account for both the temporal and spatial characteristics of the adaptive optical system exist, they are complex and require detailed information regarding the …

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Object Tracking Through Adaptive Correlation, Dennis A. Montera Dec 1992

Object Tracking Through Adaptive Correlation, Dennis A. Montera

Theses and Dissertations

This paper discusses the use of a correlation based system to track, an object through a series of images based on templates derived from previous image frames. The ability to track is extended to sequences which include multiple objects of interest within the field of view. This is accomplishes by comparing the height and shape of the template autocorrelation to the peaks in the correlation of the template with the next scene. The result is to identify the region in the next scene which best matches the designated target. In addition to correlation plane postprocessing, an adaptive window is used …

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High Range Resolution Radar Target Identification Using The Prony Model And Hidden Markov Models, Mark R. Dewitt Dec 1992

High Range Resolution Radar Target Identification Using The Prony Model And Hidden Markov Models, Mark R. Dewitt

Theses and Dissertations

Fully polarized Xpatch signatures are transformed to two left circularly polarized signals. These two signals are then filtered by a linear FM pulse compression ('chirp') transfer function, corrupted by AWGN, and filtered by a filter matched to the 'chirp' transfer function. The bandwidth of the 'chirp' radar is about 750 MHz. Range profile feature extraction is performed using the TLS Prony Model parameter estimation technique developed at Ohio State University. Using the Prony Model, each scattering center is described by a polarization ellipse, relative energy, frequency response, and range. This representation of the target is vector quantized using a K-means …

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Enhancement Of Audio Localization Cue Synthesis By Adding Environmental And Visual Cues, Eric L. Scarborough Dec 1992

Enhancement Of Audio Localization Cue Synthesis By Adding Environmental And Visual Cues, Eric L. Scarborough

Theses and Dissertations

An audio localization cue synthesizer, the DIRectional Audio Display (DIRAD) was used to simulate auditory distance, room reflections, and to provide spatial audio for computer graphics images. The DIRAD processes input audio signals to generate spatially located sounds for headphone listening. The DIRAD can position audio sources around the head and these sounds are stable with respect to the listener's head position. An interactive, real-time simulation of auditory distance and room reflections was accomplished using the DIRAD in combination with a Silicon Graphics audio processor board installed in a Personal Iris 4D/35. Several demonstrations of auditory distance and the effects …

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Design Of An Artificial Neural Network Based Tactile Sensor For The Utah/Mit Dexterous Hand, Jeffery D. Nering Sep 1992

Design Of An Artificial Neural Network Based Tactile Sensor For The Utah/Mit Dexterous Hand, Jeffery D. Nering

Theses and Dissertations

The Neural Tactile Sensor (NTS) is a high resolution, easily manufactured tactile sensor consisting of electrodes, a thin resistive 'skin', and pattern recognition circuitry that is capable of resolving dynamic and static contact location, force, and slip throughout the continuum of the sensor's active region. The sensor operates by means of a resistive 'skin' harboring the electric field generated when a current is injected into it, and a plurality of electrodes for taking measurements of said electric field. When current flows through the resistive medium from the location of tactile contact, an electric field within the resistive medium is established, …

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Output Frequency Changes In A Commercial Rubidium Clock Resulting From Magnetic Field And Microwave Power Variations, Edward B. Sarosy Sep 1992

Output Frequency Changes In A Commercial Rubidium Clock Resulting From Magnetic Field And Microwave Power Variations, Edward B. Sarosy

Theses and Dissertations

This report shows the relationship between output frequency shifts and the absorption cell magnetic field during microwave power fluctuations on a commercial rubidium frequency clock. Changes in the clock output frequency relative to the 10 MHz reference were monitored as changes in the absorption cell magnetic field (0.01 to 1.0 Gauss) and changes in the cell's interrogation microwave power were varied from the nominal specification (PO) at four discrete values (+1.3. -1.1, -2.2, -4.OdB). The maximum normalized output frequency shift of 1.4x10-10 occurred at--4dB. The maximum normalized frequency change for the +1.3 and -1.1 dB data is about 3 …

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Autonomous Face Segmentation, Kevin P. Gay Sep 1992

Autonomous Face Segmentation, Kevin P. Gay

Theses and Dissertations

The purpose of this study was to implement an autonomous face segmentor as the front end to a face recognition system on a Sun SPARCStation2. Face recognition performance criteria, specifically, the capabilities to isolate and resize faces in an image to a consistent scale, were analyzed to determine current practical limitations. Face images were acquired using a S-VHS camcorder. Segmentation was accomplished using motion detection and predefined rules. Tests were run to determine the suitable of the autonomous segmentor as the front-end to a face recognition system. The segmentation system developed consistently located faces and rescaled those faces to a …

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Co-Channel Speaker Separation, Thomas S. Andrews Sep 1992

Co-Channel Speaker Separation, Thomas S. Andrews

Theses and Dissertations

In the co-channel speaker separation problem, the goal is to recover two separate speech signals from a monaural channel which contains the sum of the two speech signals. A new methodology is developed that if given that a segment of co-channel speech is separated into a stronger and weaker segment, the correct assignment of these separated segments to the appropriate talker can be made using a Linear Predictive Coding (LPC) based minimum-prediction residual computation. The uniqueness of the developed technique is that no a priori information is required of the co-channel speech signal. The information needed to appropriately assign these …

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Development Of An Analog Mimo Quantitative Feedback Theory (Qft) Cad Package, Richard R. Sating Jun 1992

Development Of An Analog Mimo Quantitative Feedback Theory (Qft) Cad Package, Richard R. Sating

Theses and Dissertations

This thesis describes the development of an analog MIMO Quantitative Feedback Theory (QFT) CAD package for the automation of the multivariable control design process. The CAD package is capable of carrying a design from problem setup through the design process to a frequency domain analysis of the compensated MIMO system. The package automates the selection of the weighting matrix, formation of the square effective plants, the polynomial matrix inverse required to form the equivalent plants, generation of stability, tracking, disturbance, gamma, and composite bounds, loop shaping, design of the prefilter elements, and the frequency domain analysis of the completed design. …

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Comparison Of Synchronization Techniques For The Afit Direct Sequence Spread Spectrum System, Edward A. Bednar Apr 1992

Comparison Of Synchronization Techniques For The Afit Direct Sequence Spread Spectrum System, Edward A. Bednar

Theses and Dissertations

The purpose of this study is to analyze and evaluate the performance of several code synchronization methods that could be used in the Air Force Institute of Technology's (AFIT) Direct-Sequence Spread Spectrum (DSSS) communication system. These methods include the sliding correlator, transmitted reference, sequential estimation, and three types of matched filters. The matched filters are the baseband matched filter, delay line matched filter, and the convolver. The criteria used for the evaluation of these synchronization methods are theoretical synchronization times and probability of bit-error. Advantages and disadvantages of each synchronization method are described and a method is recommended to be …

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Method For Gaseous Component Indentification With #3 Polymeric Film, Edward S. Kolesar Jr. Dec 1991

Method For Gaseous Component Indentification With #3 Polymeric Film, Edward S. Kolesar Jr.

AFIT Patents

A sensor having an interdigitated gate electrode field effect transistor (IGEFET) coupled to an electron beam evaporated copper phthalocyanine thin film is used to selectively detect parts-per-billion concentration levels of atmosphere contaminants such as nitrogen dioxide (NO2) and diisopropyl methylphosphonate (DIMP). The sensor is excited with a voltage pulse, and its time- and frequency-domain response are examined. The envelopes of the magnitude of the normalized difference frequency spectrums reveal features which unambiguously distinguish the NO2 and DIMP exposures.

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Binaural Sound Localization Using Neural Networks, Rushby C. Craig Dec 1991

Binaural Sound Localization Using Neural Networks, Rushby C. Craig

Theses and Dissertations

The purpose of this study was to investigate the use of Artificial Neural Networks to localize sound sources from simulated, human binaural signals. Only sound sources originating from a circle on the horizontal plane were considered. Experiments were performed to examine the ability of the networks to localize using three-different feature sets. The feature sets used were: time-samples of the signals, mena Fast Fourier Transform magnitude and cross correlation data, and auto-correlation and cross correlation data. The two different types of sound source signals considered were tones and gaussian noise. The feature set which yielded the best results in terms …

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Comparison Of Afitpac Versus Nos And A Packet Radio Network Design, Thomas A. Iannelli Dec 1991

Comparison Of Afitpac Versus Nos And A Packet Radio Network Design, Thomas A. Iannelli

Theses and Dissertations

This thesis encompasses two themes: (1) A comparison of the Network Operating System (NOS) software package, developed by Phil Karn and others, and AFITPAC, written by Marsh and Geier at the Air Force Institute of Technology. The comparison is based on the Air Force Logistics Command's requirements for the development of a Packet Radio Network program. The results of the comparison are a recommendation that use of the NOS package be pursued because it can meet all twelve of the requirements and compiles with five of the Military Standard Protocols. (2) The design of a personal computer Packet Radio Network …

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Incorporation Of Differential Global Positioning System Measurements Using An Extended Kalman Filter For Improved Reference System Performance, William J. Negast Dec 1991

Incorporation Of Differential Global Positioning System Measurements Using An Extended Kalman Filter For Improved Reference System Performance, William J. Negast

Theses and Dissertations

To quantify the performance abilities of existing or proposed navigation systems, the U.S. Air Force has, for the last several years, compared the performance of the system under test to the performance of a baseline navigation system known as the Completely Integrated Reference Instrumentation System (CIRIS). CIRIS obtains a highly accurate navigation solution by combining information from three major subsystems: inertial navigation system (INS) information, barometric altitude information, and range and range-rate information from ground transponders which have been precisely surveyed. Although the navigation solution produced by CIRIS is highly accurate, it will soon be inadequate as the standard against …

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Principal Base Parameter Analysis: Implementation And Analysis In An Adaptive Model-Based Robotic Controller, Gregory L. Showman Dec 1991

Principal Base Parameter Analysis: Implementation And Analysis In An Adaptive Model-Based Robotic Controller, Gregory L. Showman

Theses and Dissertations

Principal Base Parameter Analysis (PBPA) is a general and systematic procedure for determining the dynamic parameters that directly contribute to the joint torques of a manipulator, ranked in order of sensitivity. The feasibility of employing PBPA as an aid in the design and tuning of adaptive model-based controllers for industrial manipulators is rigorously investigated. This is accomplished by employing PBPA to determine the minimal size of the adaptive parameter vector and more importantly, to develop a less heuristic procedure for controller tuning. A simple, step-by-step procedure is developed wherein the manipulator torque equations are used in conjunction with PBPA to …

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Evaluation Of An Interdigitated Gate Electrode Field-Effect Transistor (Igefet) For In Situ Resin Cure Monitoring, Thomas E. Graham Dec 1991

Evaluation Of An Interdigitated Gate Electrode Field-Effect Transistor (Igefet) For In Situ Resin Cure Monitoring, Thomas E. Graham

Theses and Dissertations

The purpose of this study was to design an Interdigitated Gate Electrode Field-Effect Transistor (IGEFET) and evaluate its performance as an in situ resin cure monitor. A commercially available resin was selected for the research, and rheological studies were performed to identify the resin's gelation point during isothermal cures at two selected temperatures. Additional rheological studies were performed to identify the resin's glass transition temperature. The interdigitated gate electrode of the IGEFET was coated with samples of the resin, and electrical measurements were performed while the resin cured. The chemical changes which occur in the resin as a result of …

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