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Air Force Institute of Technology

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Articles 5221 - 5250 of 5698

Full-Text Articles in Engineering

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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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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Formalizing, Validating, And Verifying Real-Time System Requirements With Reacto And Vhdl, Frank C. Young Dec 1992

Formalizing, Validating, And Verifying Real-Time System Requirements With Reacto And Vhdl, Frank C. Young

Theses and Dissertations

We develop a methodology for formalizing, verifying, and validating the requirements specification of real-time systems based on a graphical and formal hierarchical Finite State Machine (FSM) language Reacto. We define a means to quantify time and express real-time constraints in Reacto and a transformation from Reacto to the Very High Speed Integrated Circuit (VHSIC) hardware Description Language (VHDL). Reacto's high level abstractions, graphical nature, and theorem prover produce efficient, accurate, and easily understood specifications. We use VHDL's event driven simulation capability, concurrency, and temporal operators to thoroughly examine temporal dependencies between the state machine transitions, and to increase simulation power …

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An Investigation Of Structural Locality In The Memory Referencing Behavior Of Computer Programs, Michael E. Bletzinger Dec 1992

An Investigation Of Structural Locality In The Memory Referencing Behavior Of Computer Programs, Michael E. Bletzinger

Theses and Dissertations

The nature of structural locality as defined by same stack distance access is investigated in this thesis. The question is whether structural locality can be characterized as an inherent type of behavior. The results revealed that structural locality is strongly influenced by a program's design and phase of execution. Entropy measurements revealed that the predictiveness of structural locality is also influenced by program design. A Markov model was refined to capture the characteristics of structural locality that were measured. Trace synthesis demonstrated some success in reproducing same stack distance run distributions when the model had enough states to encompass the …

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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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Failure Identification Using Multiple Model Adaptive Estimation For The Lambda Flight Vehicle, Peter D. Hanlon Dec 1992

Failure Identification Using Multiple Model Adaptive Estimation For The Lambda Flight Vehicle, Peter D. Hanlon

Theses and Dissertations

This study develops and investigates the performance of a Multiple Model Adaptive Estimator (MMAE) to detect and identify control surface and sensor failures on the LAMBDA flight vehicle (a URV developed by Wright Laboratories). The MMAE uses a bank of Kalman filters that predict the aircraft response to a given input, with each filter model based on a different failure hypothesis, and then forms the residual difference between the prediction and sensor measurements for each filter. The MMAE uses these residuals to determine the probabilities of the failures that are modeled by the Kalman filters. Initially the MMAE identified all …

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Etann Hardware Implementation For Radar Emitter Identification, James B. Calvin Jr. Dec 1992

Etann Hardware Implementation For Radar Emitter Identification, James B. Calvin Jr.

Theses and Dissertations

This study investigated classification of 30 radar emitters with 16 signal features using Intel's 80170NX chip, the Electronically Trainable Analog Neural Network (ETANN). Software tools were developed to characterize the ETANN sigmoidal transfer function for use in a custom simulator, known as Neural Graphics. Neural Graphics operates on a Silicon Graphics workstation. The Intel Neural Network Training System simulators were used in early experiments, but were found to be inefficient in training on data used in this research. Using a modified Neural Graphics simulator, single chip and multi-chip experiments were performed to provide benchmark results prior to performing chip-in-loop training. …

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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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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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Digital Signal Processing Using Lapped Transforms With Variable Parameter Windows And Orthonormal Bases, Brian D. Raduenz Dec 1992

Digital Signal Processing Using Lapped Transforms With Variable Parameter Windows And Orthonormal Bases, Brian D. Raduenz

Theses and Dissertations

This thesis develops and evaluates a number of new concepts and tools for the analysis of signals using variable overlapped windows and orthonormal bases. Windowing, often employed as a spectral estimation technique, can result in irreparable distortions in the transformed signal. By placing conditions on the window and incorporating it into the orthonormal representation, any signal distortion resulting from the transformation can be eliminated or cancelled in reconstruction. This concept is critical to the theory underpinning this thesis. As part of this evaluation, a tensor product based general N-point fast Fourier transform algorithm was implemented in the DOD standard language, …

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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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Acquisition Of Direct Sequence Spread Spectrum Signals Using Digital Signal Processing Techniques, Ronald E. Schmitz Dec 1992

Acquisition Of Direct Sequence Spread Spectrum Signals Using Digital Signal Processing Techniques, Ronald E. Schmitz

Theses and Dissertations

This thesis investigates the use of digital signal processing (DSP) techniques to achieve initial synchronization with Global Positioning System (GPS) Pseudo-Noise (PN) signals. Synchronization with the transmitted PN signal is essential to the despreading of the transmitted Direct Sequence Spread Spectrum (DS/SS) signals and decoding of the transmitted satellite data. The use of DSP methods to decrease the time required to achieve initial synchronization is investigated. This thesis proposes an initial acquisition section of the GPS receiver and derives the equations to show the method is mathematically feasible. Computer simulations of the proposed receiver using received signals corrupted by Doppler …

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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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An Object-Oriented Computer Aided Design Program For Modern Control Systems Analysis, Frederick L. Trevino Dec 1992

An Object-Oriented Computer Aided Design Program For Modern Control Systems Analysis, Frederick L. Trevino

Theses and Dissertations

This investigation is a continuation of the ICECAP-PC research project conducted under Prof. Gary B. Lamont at the Air Force Institute of Technology. It is an ongoing development of a public domain Computer Aided Design (CAD) package for Control Engineering students and faculty, with a special emphasis on education. This investigation focuses on three areas. First, an object-oriented environment is specified, designed and implemented. The functional structure of ICECAP-PC is then converted into an object-oriented structure because object-orientation provides an advanced logic and implementation structure and effectively addresses common software engineering issues. Additionally, a new interface featuring pull-down menus, mouse …

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Detection Of Spoofing, Jamming, Or Failure Of A Global Positioning System (Gps), Juan R. Vasquez Dec 1992

Detection Of Spoofing, Jamming, Or Failure Of A Global Positioning System (Gps), Juan R. Vasquez

Theses and Dissertations

The Air Force has equipped its aircraft with avionic systems such as Global Positioning System (GPS) and Inertial Guidance Systems (INS) capable of providing accurate navigation solutions. The aircrews flying these aircraft require a system that can either survive the hostile environments encountered in combat or notify the aircrew that their performance has been significantly degraded. This research focuses on failure detection and isolation techniques using an extended Kalman filter and generalized likelihood ratios using matched filters. Analysis is conducted using a Kalman filter development package known as the Multimode Simulation for Optimal Filter Evaluation (MSOFE). Both a large order …

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Face Recognition With Neural Networks, Dennis L. Krepp Dec 1992

Face Recognition With Neural Networks, Dennis L. Krepp

Theses and Dissertations

This study investigated neural networks for face verification and classification. The research concentrated on developing a neural network based feature extractor and/or classifier to perform authorized user verification in a realistic work environment. Recognition accuracy, system assumptions, training time, and execution time were analyzed to determine the feasibility of a neural network approach. Data was collected using a camcorder and two segmentation schemes: manual segmentation and motion-based, automatic segmentation. Data consisted of over 2000. 32x32 pixel, 8 bit gray scale images of 52 subjects; each subject had two to ten days worth of images collected. Several training and test sets …

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Signal Approximation With A Wavelet Neural Network, Charles M. Westphal Dec 1992

Signal Approximation With A Wavelet Neural Network, Charles M. Westphal

Theses and Dissertations

This study investigated the use of Wavelet Neural Networks (WNN) for signal approximation. The particular wavelet function used in this analysis consisted of a summation of sigmoidal functions (a sigmoidal wavelet). The sigmoidal wavelet has the advantage of being easily implemented in hardware via specialized electronic devices like the Intel Electronically Trainable Analog Neural Network (ETANN) chip. The WNN representation allows the determination of the number of hidden-layer nodes required to achieve a desired level of approximation accuracy. Results show that a bandlimited signal can be accurately approximated with a WNN trained with irregularly sampled data. Signal approximation, Wavelet neural …

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Excitation And De-Excitation Mechanisms Of Er-Doped Gaas And Algaas, David W. Elsaesser Dec 1992

Excitation And De-Excitation Mechanisms Of Er-Doped Gaas And Algaas, David W. Elsaesser

Theses and Dissertations

Electrical and optical characterization have been performed on GaAs and AlxGa1-xAs samples doped with Er either by ion implantation or during Molecular Beam Epitaxial (MBE) growth. Deep Level Transient Spectroscopy (DLTS) and Temperature-Dependent Hall Effect (TDH) measurements indicated the presence of two hole traps in Er-doped GaAs, at 35 and 360 meV above the valence band maximum. The former (shallower) center was thought to be due to Er substituting for a Ga atom (ErGa) and giving rise to an isoelectronic impurity potential. The second center was attributed to an Er atom occupying an interstitial …

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An Experimental Determination Of The Effects Of Blending Collocated And Non-Collocated Sensor Measurements To Control A Flexible Structure, Richard G. Cobb Dec 1992

An Experimental Determination Of The Effects Of Blending Collocated And Non-Collocated Sensor Measurements To Control A Flexible Structure, Richard G. Cobb

Theses and Dissertations

An experimental investigation was performed controlling a cantilevered beam in bending using proportional feedback on a blend of collocated and non-collocated sensor measurements using a single actuator. Exact transfer functions between the control input and the measurements were developed and compared to the finite element method. By analyzing the open loop pole-zero locations as a function of the measurement blending, insight into the closed loop behavior is obtained. Minimum phase behavior can be maintained for a range of the blending ratio. Results using blended control were compared to both proportional collocated feedback and compensated collocated feedback using LQG methods. The …

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Canonical Floquet Perturbation Theory, David J. Pohlen Dec 1992

Canonical Floquet Perturbation Theory, David J. Pohlen

Theses and Dissertations

Classical Floquet theory is examined in order to generate a canonical transformation to modal variables for periodic system This transformation is considered canonical if the periodic matrix of eigenvectors is symplectic at the initial time. Approaches for symplectic normalization of the eigenvectors had to be examined for each of the different Poincare eigenvalue cases. Particular attention was required in the degenerate case, which depended on the solution of a generalized eigenvector. Transformation techniques to ensure real modal variables and real periodic eigenvectors were also needed. Periodic trajectories in the restricted three-body case were then evaluated using the canonical Floquet solution. …

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A Study Of Heat Flux Induced Dryout In Capillary Grooves, Timothy J. Murphy Dec 1992

A Study Of Heat Flux Induced Dryout In Capillary Grooves, Timothy J. Murphy

Theses and Dissertations

This is an experimental study of ethanol flowing in the narrow grooves of a copper plate which is subjected to heat fluxes sufficient to evaporate more liquid than can be replaced by capillary pumping. Three groove geometries are used: square, rectangle, and trapezoid. The objective is to simulate aspects of liquid flow in heat pipes with axial grooves. In order to validate analytical models of capillary flow in grooves, the capillary limit, dryout front location, and dryout front movement in response to power draw downs are documented. The results show the rewet performance of the groove is dependent on geometry. …

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The Non-Linear Dynamics Of Composite Cylindrical Shells, James M. Greer Jr. Dec 1992

The Non-Linear Dynamics Of Composite Cylindrical Shells, James M. Greer Jr.

Theses and Dissertations

The non-linear dynamic behavior of suddenly loaded composite shells is the subject of this research. The objective of research is two-fold: (1) to characterize the apparently random physical behavior sometimes observed in the finite element analysis as either numerical instability, chaotic behavior, or both; and (2) to develop criteria for choosing time steps for the finite element model, referred to as DSHELL. This displacement based finite element code is capable of dynamic analysis of plates, arches, and cylindrical shells undergoing large displacements and moderately large rotations during deformation. DSHELL uses a 36-DOF isoparametric shell element to obtain numerical results. A …

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Passive Damping Of A Solar Array, Mark A. Scharpen Dec 1992

Passive Damping Of A Solar Array, Mark A. Scharpen

Theses and Dissertations

This study was an attempt to conceptualize, design, build, and test a constrained layer damping device that uses mechanical advantage for the purpose of increasing the damping of transient vibration of a five-bay planar truss. The aluminum truss was clamped to a fixed support and simulated a solar array. A conventional constrained layer treatment was designed, built, and tested to serve as a benchmark for comparison. For the conventional treatment, Plunkett and Lee's segmented constraining layer technique was used. The improved device, two three-layer sandwich beams spanning the two bays nearest the built-in end, were supported several inches away from …

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Vibration Suppression In Large Flexible Space Structures Using Active Control Techniques, Chad T. Matheson Dec 1992

Vibration Suppression In Large Flexible Space Structures Using Active Control Techniques, Chad T. Matheson

Theses and Dissertations

This report investigates the use of active vibration control techniques applied to the PACOSS Dynamic Test Article as an experimental structure. In the course of the research, a mathematical model of the lightly damped experimental structure was created based on experimental data. This model was used in the design of two classes of controllers. The first class is pure rate feedback of the structure's measured states such that global stability is insured. The second type of controller investigated was an optimal controller (LQG) that was created using the truncated mathematical model. The rate feedback controller showed significant improvements in the …

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Baseline Experiments On Coulomb Damping Due To Rotational Slip, John P. Santacroce Dec 1992

Baseline Experiments On Coulomb Damping Due To Rotational Slip, John P. Santacroce

Theses and Dissertations

Two experimental pin-type joint models are developed to study the effects of Coulomb Damping due to rotational slip. Model One is an inverted beam allowed to pivot at one end as a pendulum. Model Two is a horizontally mounted beam allowed to pivot about its center. The equations of motion for the joint geometries, considering only macro-slip friction, are developed and solved. Theoretical and experimental results for the response of the models in vibration are presented showing energy dissipation versus clamping force for the joint(s).

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Behavior Of A Quasi-Isotropic Ply Metal Matrix Composite Under Thermo-Mechanical And Isothermal Fatigue Loading, Karl A. Hart Dec 1992

Behavior Of A Quasi-Isotropic Ply Metal Matrix Composite Under Thermo-Mechanical And Isothermal Fatigue Loading, Karl A. Hart

Theses and Dissertations

This study investigated the behavior of the SCS6/Ti-15-3 metal matrix composite with a quasi-isotropic layup when tested under static and fatigue conditions. Specimens were subjected to in-phase and out-of-phase thermo- mechanical and isothermal fatigue loading. In-phase and isothermal loading produced a fiber dominated failure while the out-of-phase loading produced a matrix dominated failure. Also, fiber domination in all three profiles was present at higher maximum applied loads and al three profiles demonstrated matrix domination at lower maximum applied loads. Thus, failure is both profile dependent and load equipment. Additional analyses, using laminated plate theory, Halpin-Tsai equations, METCAN, and the Linear …

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An Experimental Investigation Of A Finite Circulation Control Wing, John M. Tallarovic Dec 1992

An Experimental Investigation Of A Finite Circulation Control Wing, John M. Tallarovic

Theses and Dissertations

This wind tunnel investigation examined the lift, drag, and pitching moment of a 20% thick, 8.5% camber, partial elliptical cross-section, single blowing slot, rectangular, circulation control wing. The aspect ratios tested were 3.71 and 3.99. Variables included three differently shaped trailing edge Coanda surfaces and steady blowing and pulsed blowing. The test Reynolds number, based on the chord was 500,000. The-angle of attack was varied from minus 6 degrees to the inception of stall. The maximum lift coefficient measured was 3. 17 with an equivalent drag coefficient of 1.85. Results also show a limit to increasing lift by increasing the …

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Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Under Tension-Tension And Tension-Compression Loading, Frank A. Opalski Dec 1992

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Under Tension-Tension And Tension-Compression Loading, Frank A. Opalski

Theses and Dissertations

A study was conducted which investigated the behavior of a cross-ply [0/90]2S Nicalon/Calcium-Aluminosilicate (Nicalon/CAS) ceramic matrix composite at room temperature under tension-compression fatigue loading. Material behavior and damage was recorded by stress-strain curves, elastic modulus, hysteretic energy density, and acetate replication techniques. Tension-tension fatigue tests at a load ratio R of 0.1 (R = σmin/σmax) were completed which determined that 140 MPa was the maximum stress allowable in which cycle runout (1,000,000 cycles) would occur. Above this value, transverse crack density increased with respect to cycles and failure ultimately occurred. Tension-compression tests were then performed …

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A Wind Tunnel Study Of Magnus Effects On A Differentially Rotating Missile, Karen A. Naselius Dec 1992

A Wind Tunnel Study Of Magnus Effects On A Differentially Rotating Missile, Karen A. Naselius

Theses and Dissertations

This study investigates magnus effects on a non-firmed missile model which had three axially rotating sections that span at different rates. Five spin cases are examined; the mid section spinning only; the front and rear sections spinning only; all section spinning at the same speed; all sections spinning in the same direction with the mid section spinning at an additional ten revolutions per second; and all sections spinning with the mid sections spinning the opposite direction at an additional ten revolutions per second. These five cases are tested at three different spin rates for two different wind tunnel velocities. Since …

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