Digital Commons Network^™

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 …

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 …

Speech Coding And Compression Using Wavelets And Lateral Inhibitory Networks, Richard Ricart

Theses and Dissertations

The purpose of this thesis is to introduce the concept of lateral inhibition as a generalized technique for compressing time/frequency representations of electromagnetic and acoustical signals, particularly speech. This requires at least a rudimentary treatment of the theory of frames-which generalizes most commonly known time/frequency distributions--the biology of hearing, and digital signal processing. As such, this material, along with the interrelationships of the disparate subjects, is presented in a tutorial style. This may leave the mathematician longing for more rigor, the neurophysiological psychologist longing for more substantive support of the hypotheses presented, and the engineer longing for a reprieve from …

Characterization Of An Air-To-Air Optical Heterodyne Communication System, Rebecca N. Seeger

Theses and Dissertations

The primary goal of this research was to determine the feasibility of air-to-air optical communications systems using coherent detection in a turbulent environment. Secondary goals were to determine (1) the signal-to-noise ratio (SNR) degradation due to turbulence and (2) the effect of varying the wavelength (1.5, 830, 904 nm), altitude (5000-12500 m), path length (40-160 km) and aperture side length (1-15 cm) on the turbulence affected SNR. The research was conducted under the following assumptions: (1) ideal transmitter and receiver, (2) equally sized, uniformly weighted, square transmitter and receiver apertures, (3) ideal tracking by the receiver, and (4) zero losses …

Radar Image Processing For The Afit Anechoic Chamber, Brian K. Sanders

Theses and Dissertations

The purpose of this study was to begin development of an Inverse Synthetic Aperture Radar imaging capability for the AFIT anechoic chamber. This began with an evaluation of the capabilities and limitations of the existing radar system and the chamber itself for this application. Then, after deciding on the image processing approach, software had to be written to collect the data necessary for image processing. This constituted the majority of this study, and resulted in a versatile, user-friendly program that automates the process of collecting data for high-resolution radar images. The program checks that the data to be collected will …

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 …

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 …

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 …

Optical Image Segmentation Using Wavelet Filtering Techniques, Christopher P. Veronin

Theses and Dissertations

This research effort successfully implemented an automatic, optically based image segmentation scheme for locating potential targets in a cluttered FLIR image. Such a design is critical to achieve real-time segmentation and classification for machine vision applications. The segmentation scheme used in this research was based on texture discrimination and employs orientation specific, bandpass spatial filters as its main component. The orientation specific, bandpass spatial filters designed during this research include symmetrically located circular apertures implemented on heavy, black aluminum foil; cosine and sine Gabor filters implemented with detour-phase computer generated holography photoreduced onto glass slides; and symmetrically located circular apertures …

Energy Transfer In Singlet Oxygen And Bromine Monofluoride, Barrett F. Lowe

Theses and Dissertations

The interhalogen molecule, bromine monofluoride (BrF), is currently under study as a potential candidate for a visible chemical laser medium. Previous studies have shown a strong emission from BrF(B³π(O⁺)) in the presence of singlet oxygen. While singlet oxygen will pump BrF(X) to BrF(B), the exact mechanism is not known. Chemiluminescence observed from BrF(B) excited by oxygen in a gas flowtube was used to study the energy transfer mechanism. The objective of this research was fourfold. First, the pumping process was identified as a 3- Body Mechanism. Second, the observed vibrational distribution clearly showed the population of …

Low Temperature Photoluminescence Study Of Holmium And Thulium Implanted Into Iii-V Semiconductors And Silicon, Eric Silkowski

Theses and Dissertations

Low temperature photoluminescence studies were performed on holmium implanted into InP, GaAs, and Si; and thulium implanted into AlGaAs, GaAs, and Si. Samples were annealed by the conventional furnace and rapid thermal techniques. None of the characteristic 4f emissions of holmium were found in the spectral region of .73 to 1.55 eV. AlGaAs:Tm showed strong thulium emissions in the .93 to 1.03 eV region. These emissions were studied and compared to those in GaAs:Tm. Low and high temperature annealed samples showed evidence of trivalent Tm centers. Temperature dependence studies showed that thulium 4f emissions were present above 200 K but …

A Procedure For Performance Assessment Of Drugs Hypothesized To Be Effective In Controlling Motion Sickness, Zainab N. Ahmed

Theses and Dissertations

The Air Force Institute of Technology (AFIT) is conducting research into the effectiveness of certain drugs for controlling motion sickness. If the drugs are found to be useful, they must still be proven to have no harmful effects on the operator's performance abilities. There are many methods for assessing performance effects of drugs but very little standardization exists. The Unified Tri-Services Cognitive Performance Assessment Battery (UTC-PAB) is a performance assessment method designed to be used by all military branches. This will encourage standardization of drug testing, exchange of data, and comparability of methods. Five tests were chosen from the UTC-PAB …

Debris Production In Hypervelocity Impact Asat Engagements, Stephen K. Remillard

Theses and Dissertations

This study reviews laboratory experiments on hypervelocity impacts and applies the results from those experiments to predict the mass of debris produced, the number of particles, and the size distribution of the debris particles produced in an ASAT engagement using kinetic energy weapons. The three possible types of hypervelocity collisions are discussed and parameters are provided that will help predict what type of collisions will occur between a given projectile and a target satellite. Once the collision type is determined, various equations are supplied which can be used to calculate debris mass, etc. Next, a notional attack between a miniature …

Proposed Design Of A Tactical Reconnaissance Satellite System, John D. T. Severance

Theses and Dissertations

Tactical reconnaissance is a much needed wartime asset, yet with the deactivation of all active-duty RF-4C squadrons world-wide there appears to be a gap in this country's war-fighting capability. This study proposes a system which utilizes a constellation of small tactical satellites and mobile ground receiving stations that can fulfill the tactical reconnaissance mission. A literature review gives background information on resolution variables, the RF-4C, space reconnaissance, and sensing technologies. After defining system requirements and constraints, a basic system concept is determined. Three alternative systems, separated mostly by threat scenario, technology, and cost, are evaluated using Athey's Systematic Systems Approach. …

Measuring The Effectiveness Of Space: Satellite Weather Systems, Steven T. Wilson

Theses and Dissertations

Using concepts from multivariate utility theory, basic orbital mechanics, and information regarding operational and planned meteorological satellites, this thesis develops a meaningful MOE to support high-level decision making regarding the allocation, acquisition, and operational deployment of space meteorological satellite (METSAT) assets. Satellite meteorological systems were chosen because of the ready availability of pertinent unclassified data. However, the methodology presented may be applied to any type of space system.

Freedom Of Information And Open Records Laws: Aid Or Hindrance To Government?, Chase H. Boardman

Theses and Dissertations

No abstract provided.

Artificial Intelligence And Its Influence On The Public Accounting Profession, Mark A. Johnson

Theses and Dissertations

No abstract provided.

Development Of A Piezoelectric Polymer Film Pressure Transducer For Low Frequency And Dynamic Pressure Measurement, Ted H. Halley

Theses and Dissertations

The purpose of this research was to investigate the characteristics of a small and inexpensive pressure transducer made from piezoelectric film. The pressure transducer was designed to be small and surface mountable so that the pressure distribution could be measured on an aerodynamic body. A charge reset technique was used to overcome the traditional limitations, low frequency measurements and charge decay, of a piezoelectric device.

Analysis Of Hypersonic Blunt-Body Flows Using A Total Variation Diminishing Scheme And The Maccormack Scheme, Montgomery C. Hughson

Theses and Dissertations

An explicit second-order accurate, total variation diminishing (TVD) scheme and the MacCormack scheme are applied to the Euler equations in axisymmetric form to study hypersonic blunt body flows. The modified flux approach of Harten, with modification by Yee, for two-dimensional flows is extended to treat axisymmetric flows. Calculated flow properties for the steady state, blunt body problem such as shock standoff distance, bow shock shape, surface pressure distribution and entropy jump conditions are compared to theory, results from the MacCormack scheme, and experimental data for Mach numbers of 3.0, 4.03, 5.06, 6.03 and 8.1. Additionally, the TVD and MacCormack schemes …

H2 And H∞ Optimization With A Restricted Region Of Stability, Michael J. Mares

Theses and Dissertations

Many modern control design methods, such as H₂ and H_∞ optimization, guarantee that the closed-loop system will be stable. To make further use of this guarantee, the portion of the s-plane considered to be stable is restricted to a region left of a vertical line some distance alpha from the imaginary axis. This alpha shift was accomplished in the state space equations, so standard computational tools still work. now the system is not only guaranteed to be stable, but also has some guaranteed speed for the time response. The equations for guaranteeing some arbitrary damping ratio were also …

An Experimental Study Of A Sting-Mounted Single-Slot Circulation Control Wing, Michael E. Pelletier

Theses and Dissertations

This wind tunnel study investigated the feasibility of using a sting and force balance to measure the aerodynamic forces and moments on a circulation control wing. A 20% this, 8.5% camber, single blowing slot, rectangular wing was designed, built, and tested in the AFIT 5-ft wind tunnel. Lift and drag coefficients were referenced to the stability axis. The Reynolds number for all tests was 950,000; angle of attack was varied from -6 to +6 degrees. Trends in the data were similar to two dimensional data, with the exception of high drag coefficients with increased blowing. Results show it is feasible …

Impact Damage In Curved Graphite/Epoxy Panels With Clamped Edges, Ronald B. Perry

Theses and Dissertations

Graphite/epoxy curved cylindrical panels were impacted in the center by an impact machine capable of measuring load during the test. Load, deflection and strain as functions of time were measured for six symmetric layup configurations for impact energies of 0.5 to 4.5 ft-lb. Damage was produced in all panels for certain impact energies. The extent and location of damage was determined from C-scans and optical microscopy of panel cross-sections. The cross-sections indicated that both delamination and transverse cracking contribute to internal damage. An in-house nonlinear finite element code was used to predict the panel deflections and stresses. The analysis produced …

A Linear Quadratic Regulator Weight Selection Algorithm For Robust Pole Assignment, Jeffrey D. Robinson

Theses and Dissertations

An advantage of linear quadratic regulator (LQR) design is that it gives a robust system by guaranteeing stability margins. This property is used to develop an algorithm for placing robust poles. The algorithm chooses the positive semidefinite weighting matrix Q and positive definite weighting matrix R by attempting to place closed loop poles at a set of desired poles. If the desired poles lie outside the allowable LQR region, the algorithm finds the achievable poles inside the region that are closest to the desired poles. The solution requires using a gradient search technique to minimize a weighted eigenvalue difference cost …

Modelling And Analysis Of Kernel Function And Development Of Equivalent Theodorsen Function For Three-Dimensional Aeroelastic Analysis, John K. Ryder

Theses and Dissertations

A fractional calculus model is developed for the kernal function under incompressible subsonic flow conditions for rectangular planform airfoils with small aspect ratio. A model valid for restricted regions of the kernel function for compressible subsonic flow conditions is also developed. Additionally, a method for numerically solving the pressure-downwash integral equation for rectangular planform wings of aspect ratio two through ten in incompressible flow is developed. An equivalent Theodorsen function for three- dimensional unsteady flow is developed, enabling the use of simpler two- dimensional aeroelastic equations of motion to fully capture the more complicated three-dimensional effects.

Investigation Of Damage Mechanisms In A Cross-Ply Metal Matrix Composite Under Thermo-Mechanical Loading, Joel J. Schubbe

Theses and Dissertations

Metal matrix composites (MMCs) are rapidly becoming strong candidates for high temperature and high stiffness structural applications such as the Advanced Tactical Fighter (ATF). This study systematically investigated the failure modes and associated damage in a cross-ply, [0/90]_2s SCS6/Ti-15-3 metal matrix composite under in-phase and out-of-phase thermomechanic fatigue. Initiation and progression of fatigue damage were recorded and correlated to changes in Young's Modulus of the composite material. Experimental results show an internal stabilization of reaction zone size but degradation and separation from constituent materials under extended cyclic thermal loading. Critical to damage were transverse cracks initiating in the 90° …

Realistic Orbits About The Martian Moons, Samuel R. Bryant

Theses and Dissertations

Orbits about the Martian moons, Phobos and Deimos, previously found to be stable by the Poincare surface of section technique in a restricted three- body system, were investigated with non-zero eccentricity of the moons added to the dynamics of the planar four-body system (Mars, moon sun, artificial satellite). Although not strictly applicable to this case, the surface of section technique was used to verify whether or not the previously found stable orbits were realistic when a real world perturbation was added to the system dynamics. The surface of section technique involves the numerical integration of several orbits with the same …

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. …

Using Error Detection And Correction Coding For A Turbulent Atmospheric Optical Communications Link, Mark A. Cloutier

Theses and Dissertations

Probability of bit error (Pb) performance for a turbulent, atmospheric, optical, communications link with convolutional error detection and correction coding was investigated. The codes investigated were all rate 1/2 codes with constraint lengths ranging from 3 to 7. It was assumed that the coded data stream was sufficiently interleaved so that the turbulent channel could be considered memoryless. A theoretical bound on P_b, given by Viterbi for a memoryless channel, was used to plot curves of P_b versus the signal intensity of last transmitter. These curves were plotted for three different levels of atmospheric turbulence and three …

A Quantitative Analysis Of The Effects Of Adenosine And Hypoxia On The Proliferative Capacity Of Bovine Retinal Microvascular Pericytes In Vitro., Jon A. Jackson

Theses and Dissertations

The purpose of this study was to determine the effects of adenosine and hypoxia on the proliferation of microvascular pericytes from bovine retina. This was accomplished through: (1) development of in vitro methods which allowed consistent isolation and propagation of homogeneous retinal pericyte cultures; (2) manipulation of oxygen partial pressure in the culture chamber; (3) culture of retinal pericytes in physiologically relevant concentrations of various vasoactive substances.Retinal pericytes were obtained, by homogenization and enzyme digestion, from aseptically isolated bovine retinal vessels. Efficacy of the culture methods in generating a homogeneous population of pericytes was determined using immunocytochemical markers of microvascular …

Perceptions Of School Administrators Of The Nurses' Roles In A School Health Program, Vida A. Gorsegner

Theses and Dissertations

Nursing roles in school health programs differ within various school settings. These roles range from traditional nursing activities to nurse practitioner and mental health nurse roles. Literature specific to the roles of nurses in a school health program is limited; however, studies indicate that the school nurse role is multidimensional. Role theory was the framework used for this study. The purpose of this study was to determine school administrators' perceptions of the role of the nurse in a school health program.

The sample profile included 48 school administrators from a two county area in an upper midwest area. The two …