Electrical and Computer Engineering Commons^™

Determination Of Bistatic Radar Clutter Power From Topographic Data, Clyde R. Heddings

Theses and Dissertations

The purpose of this research was to develop a procedure for estimating the average bistatic radar clutter power from a topographic map using rough surface scattering theory. First, the terrain in the radar target area was divided into sub regions having homogeneous characteristics. A joint Gaussian distribution for the surface heights was fitted from the information contained in the topographic map contour lines for each homogeneous area. From these distributions, the normalized radar cross section for each terrain area was determined. The clutter power for each range cell was then determined via a modified radar range equation. The procedure was …

A Robust Digital Flight Control System For An Unmanned Research Vehicle Using Discrete Quantitative Feedback Theory, Donald J. Lacey Jr.

Theses and Dissertations

This thesis describes application of digital multiple-input multiple- output (MIMO) Quantitative Feedback Theory (QFT) technique to the design of a three axis rate controller for the Lambda Unmanned Research Vehicle. The resulting robust controller performs well throughout the flight envelope without gain scheduling. It results from research done at the Air Force Institute of Technology. The Lambda URV was designed by the Control Systems Development Branch of the Wright Laboratory at Wright-Patterson AFB, OH for flight testing aircraft control hardware and software. The flight control system is built using a small perturbation linear model developed from flight test data. The …

An Investigation Of A Design For A Finite-Difference Time Domain (Fdtd) Hardware Accelerator, James R. Marek

Theses and Dissertations

This study investigated increasing the speed of Finite-Difference Time Domain (FDTD) cell calculations through a special purpose architecture using Very Large Scale Integration (VLSI). These FDTD cell equations model inhomogeneous, isotropic, lossy magnetic and dielectric materials. Special attention was given to simplicity and performance, using the fastest components generally available in AFIT VLSI programs, while attempting to minimize component count. A VHSIC Hardware Description Language simulation of the proposed chip established design feasibility and provided performance estimates: 350 ns to generate the first cell value, 200 ns thereafter (30 MFLOPS maximum double-precision). This study also implemented boundary conditions in hardware …

Sensing Refractive Turbulence Profiles Using Wave Front Slope Measurements From Two Reference Sources, Michael D. Rejack

Theses and Dissertations

This thesis examines a remote sensing technique for measuring the atmospheric structure constant as a function of altitude by performing spatial correlation or wavefront sensor measurements. Two point sources are used to irradiate two wavefront sensors in the aperture plane of an optical system. The geometric relationship between the sources and the sensors gives rise to crossed optical paths. At the point where the paths cross, the correlation value of the turbulence contributions will be at a peak. The correlation is shown to be mathematically related to the structure constant in terms of an integral of the structure constant multiplied …

Image Segmentation Using Affine Wavelets, Steven E. Smiley

Theses and Dissertations

This thesis discusses the use of the multiresolution representation and Radial Basis Function (RBF) neural networks to segment both FLIR and SAR imagery. The multiresolution approximation coefficients are used as features into the RBF network which learns to distinguish between different cultural and natural regions or objects. The wavelets used are Mallat's spline wavelet and Daubechies' compactly supported wavelets. Additionally, this thesis provides an explanation of wavelets in a tutorial manner. It introduces wavelet theory and discusses two different approaches to generating the multiresolution or wavelet representation.

Face Recognition With The Karhunen-Loeve Transform, Pedro F. Suarez

Theses and Dissertations

The major goal of this research was to investigate machine recognition of faces. The approach taken to achieve this goal was to investigate the use of Karhunen-Loe've Transform (KLT) by implementing flexible and practical code. The KLT utilizes the eigenvectors of the covariance matrix as a basis set. Faces were projected onto the eigenvectors, called eigenfaces, and the resulting projection coefficients were used as features. Face recognition accuracies for the KLT coefficients were superior to Fourier based techniques. Additionally, this thesis demonstrated the image compression and reconstruction capabilities of the KLT. This theses also developed the use of the KLT …

Electromagnetic Scattering From Dielectric Pyramidal Tips, Albert D. Tyson Iv

Theses and Dissertations

This thesis investigated the electromagnetic scattering from conducting, lossless dielectric, and lossy dielectric (absorber) pyramids. The backscatter from pyramids was measured and a time gate was applied to isolate the scattering from the tips. The measured results were compared to predictions from an approximate Uniform Theory of Diffraction (UTD) solution for scattering by a dielectric corner. The accuracy of the corner diffraction solution was found to be dependent on the polarization of the incident electric field. The accuracy of the UTD solution was also dependent on the aspect angle to the pyramid: the UTD solution gave a nominally correct answer …

An Investigation Of The Application Of Artificial Neural Networks To Adaptive Optics Imaging Systems, Andrew H. Suzuki

Theses and Dissertations

Recurrent and feedforward artificial neural networks are developed as wavefront reconstructors. The recurrent neural network studied is the Hopfield neural network and the feedforward neural network studied is the single layer perceptron artificial neural network. The recurrent artificial neural network input features are the wavefront sensor slope outputs and neighboring actuator feedback commands. The feedforward artificial neural network input features are just the wavefront sensor slope outputs. Both artificial neural networks use their inputs to calculate deformable mirror actuator commands. The effects of training are examined.

Feature Extraction For Pose Estimation. A Comparison Between Synthetic And Real Ir Imagery, Donald J. Willis

Theses and Dissertations

This research addressed the problem of pose estimation of three- dimensional objects given their two-dimensional IR imagery and corresponding synthetic (computer-generated) IR imagery. Features and techniques were investigated to find those which may be extendable from computer models to real- world IR imagery. GTSIG and SCNGEN were used to create the synthetic imagery. Silhouette and outline shape moments were explored as optimum features for the comparison. Employing back-propagation with momentum as the training paradigm, a two-hidden-layer neural network was able to determine the base-plane orientation of the synthetic imagery to within 7.5 degrees with better than 90% accuracy. (No conclusive …

Back-Contact Vertical-Junction Solar Cell And Method, Michael W. Carver, Edward S. Kolesar Jr.

AFIT Patents

An interdigitated back-contact vertical-junction solar cell which utilizes an anisotropically etched 110-oriented silicon crystal wafer. The cell structure includes rounded corner top edges of the between cell channel walls in order to improve light capturing ability and also has pn-junctions disposed over all of the cavity internal surfaces. Additional pn-junctions are located on the rear surface of the cell array to assist in generated carrier collection into a rear mounted metallic conductor grid. The disclosed cell has desirable transducer efficiency, without the use of anti-reflection coatings, and previous improved physical robustness, and radiation hardening. Fabrication of the cell array includes …

Electrical Characterization Of Metal‐Insulator‐Semiconductor Diodes Fabricated From Laser‐Ablated Yba2Cu3O7−Δ/Yttria‐Stabilized Zirconia Films On Si Substrates, Eric M. Ajimine, Felino E. Pagaduan, M. Mahmudur Rahman, Cary Y. Yang

Electrical and Computer Engineering

The purpose of this investigation is to study the electrical properties of the YBCO/YSZ/Si metal‐insulator‐semiconductor structure and the yttria‐stabilized zirconia (YSZ)/Si interface. The YBCO and YSZ layers were epitaxially grown in situ on Si by pulsed laser deposition. Current‐voltage measurements of devices fabricated on p‐type Si(100) showed a small leakage current density at 292 K, which decreased further at 80 K. Comparison of capacitance‐voltage measurements at 292 K for frequencies between 10 and 400 kHz showed a large variation of capacitance in the accumulation region demonstrating the presence of mobile ions in the YSZ layer. This variation is less pronounced …

Comparison Of Spice And Network C Simulation Models Using The Cam System, Wen-Tsung Yen

Dissertations and Theses

The performance of SPICE and Network C (NC) circuit simulator when simulating MOS transistor circuits has been investigated and compared. SPICE analog model, NC analog model and NC MOS_PWL model are the three MOS transistor models being used. The comparison between SPICE and NC includes five areas. They are MOS transistor model, circuit analysis and computational methods, limitation on the ability to simulate circuits containing the MOS transistor diode configuration, run time and the ability to build new circuit component models using derived equations.

The prototype circuit being used is the Content-Addressable Memory (CAM) circuit. The CAM circuit is a …

Improved Efficiency In Semiconducting Polymer Light-Emitting Diodes, David Braun, A. J. Heeger, H. Kromer

Electrical Engineering

We report visible light emission from metal-polymer diodes made from semiconducting polymers, with indium-tin oxide as the “ohmic” contact, and a variety of metals as the barrier metal. Our results, which confirm the discovery by the Cambridge group [Nature347, 539 (1990)], demonstrate that light-emitting diodes can be fabricated by casting the polymer film on indium-tin oxide from solution with no subsequent polymer processing or heat treatment required. Electrical characterization reveals diode behavior with rectification ratios greater than 105 at sufficiently high voltages. Use of an electrode material with low work function leads to more than an order of magnitude improvement …

Analysis Of Baseband Equivalent Noise In A First-Order Correlation Loop Utilizing Filtered Pseudonoise Signals, Kurt Louis Kosbar, Christopher J. Scholten

Electrical and Computer Engineering Faculty Research & Creative Works

Conventional direct-sequence and frequency-hopping spread spectrum systems utilize delay-lock loops to track the timing epoch of pseudonoise codes. These devices perform admirably at high signal-to-noise ratios (SNR), however, they are suboptimal at moderate and low SNR. A correlation loop that employs appropriately filtered pseudonoise signals for the local cross-correlation waveform may have superior performance under these conditions. The performance of this modified correlation loop will be determined by the cross correlation function of the transmitted waveform and locally generated reference signals, along with the statistics of the baseband equivalent noise process. In this work, we find the statistics of the …

Comparative Analysis Of Guidance Algorithms For The Hyper Velocity Missile And Afti/F-16, Edward G. Rice

Theses and Dissertations

This project has provided me with endless intrigue. In considering the problem of guiding a hyper-velocity missile from a moving platform to a moving target, a common perception said it was just another Kalman Filtration design challenge. I began with lofty intentions of running a full up extended Kalman filter simulation but I became enthralled with the limited work available on the physical limitations of basic guidance algorithms. This became the emphasis of this project. The best filter scheme cannot overcome a guidance algorithms physical limitation. Only with an understanding of these limitations can one effectively integrate a guidance scheme …

Steady-State Production And Quenching Of Br(2P½), Ralph F. Tate

Theses and Dissertations

The spin orbit relaxation of atoms has been investigated in a steady state infrared fluorescence experiment. A CW argon ion laser operating at 488 nm was used to photodissociate gas-phase Br into equal quantities of Bromine and Bromine atoms. The resulting 2.7 µm emission was observed as a function of added quenching gas. A steady-state analysis was used to determine quenching rates for SF₆, N₂, O₂, He, Ne, Ar, Kr, and Xe, relative to quenching by the parent molecule. Limitations in the apparatus prevented determination of the quenching rate coefficient for Br₂. …

A Note On Repeated-Root Cyclic Codes, Robert H. Morelos-Zaragoza

Faculty Publications

In papers by Castagnoli et al. and Van Lint, cyclic codes with repeated roots are analyzed. Both papers fail to acknowledge a previous work by Chen, dating back to 1969, which includes an analysis of even, length binary cyclic codes. Results from Chen’s study are presented.

Application Of Mixed H2/H∞ Optimization, John J. Kusnierek

Theses and Dissertations

A non-conservative optimization technique is utilized to examine the problem of minimizing the 2 norm of one transfer function subject to an ∞-norm bound on another transfer function. For single exogenous input/ single exogenous output systems this non conservative mixed solution is shown to be up to 5% better in a specific example. For single exogenous input/two exogenous output systems the mixed solution is shown to be up to 27% better than a previous technique for a specific example. Finally, a two exogenous input/two exogenous output practical system is examined to demonstrate the utility of this mixed optimization technique.

Delay Performance Of Cebus And Modified Cebus Schemes, Altaf Hussain

Theses

In this thesis the performance of the CEBUS (Consumer Electronics Bus), a local area network proposed by the Electronics Industries Association for the 'Smart House,' is analyzed under varying network load and traffic patterns that would occur in a typical home environment. Reduced complexity versions of the CEBUS scheme are compared with the standard CEBUS scheme.

It was found from simulation analysis that the delay in the CEBUS network, at a given network bandwidth, is dependent upon the message priority and the traffic pattern in the network. It was also observed that the performance of a modified CEBUS scheme was …

Broadband Isdn Control Using Neural Networks, Stavros Zervoudakis

Theses

Broadband Integrated Services Digital Networks (B-ISDN) are considered to become the standard communications networks in the near future. Major research efford is being applied in determining the appropriate mode of operation for B-ISDN systems. Two proposals, the Synchronous Transfer Mode (STM) and the Asynchronous Transfer Mode (ATM) claim to best fit the B-ISDN transmission requirements individually. A new method for B-ISDN traffic control is proposed in this paper. This method assigns priority levels to incoming traffic while integrating STM with ATM. A neural network is used to decide how the multiplexing of the incoming packets will be performed. Several traffic …

Direct Recovering Of Surface Structure Characterized By An Nth Degree Polynomial Equation Using The Uoff Approach, Mazen A. Salhi

Theses

There are two different approaches for estimation of structure and/or motion of objects in the computer vision community today. One is the feature correspondence method, and the other is the optical flow method [1]. There are many difficulties and limitations encountered with the feature correspondence method, while the optical flow method is more feasible, but requires a substantial amount of extra calculations if the optical flow is to be computed as an intermediate step.

Direct methods have been developed [2-4], that use the optical flow approach, but avoid computing the full optical flow field as an intermediate step for recovering …

Canmol : Expert System In Medicine, Kulin Hemani

Theses

The intriguing words for the nineteen nineties are "Expert Systems", and "Artificial Intelligence". To a layman these terms conjure up thoughts of spaceships and futuristic beings. In reality they exemplify man's capability to harness technology.

Expert systems are computer software programs that make use of previously accumulated knowledge to assist in solving complex problems.

In recent years the practice of medicine has changed dramatically from a fundamentally individually deductive approach to an Artificial Intelligence based science. The modern physician no longer draws conclusions simply by examining the patient. Today the physician employs sophisticated computer based diagnostic tools to generate a …

Instrumentation And Control For A Microprocessor-Based Coronary Perfusion System, Daniel L. Priester

Master's Theses (1922-2009) Access restricted to Marquette Campus

No abstract provided.

Study Of Cathodoluminescence In Semiconductors, Mandakini V. Kale

Electrical & Computer Engineering Theses & Dissertations

Cathodoluminescence in Zn doped GaAs and ZnSe, the materials of interest for electron-beam controlled semiconductor switches, has been investigated. A new diagnostic technique, using telescopic setup of lenses, was developed to study the spatially resolved cathodoluminescence. The setup eliminated the light, other than rays from the sample, parallel to the optical axis, resulting in an enhanced spatial resolution. At high e-beam energies, light was detected, from the Zn layer region in the GaAs. It is proposed to be due to the radiative recombination of electron-hole pairs, created by the e-beam. For the polycrystalline ZnSe no light emission was detected. This …

Radiation From The Cylindrical Dielectric Taper, Tor-Odd Hoydal

Theses

The radiation problem of the cylindrical dielectric taper, excited by the HE₁₁ dominant mode, is studied. A theoretical model and a numerical investigation into the radiation characteristics of such a tapered structure are presented. The model is based upon the combination of the exact modal field solutions for a step profile cylindrical dielectric waveguide, Local Mode Theory, and the Equivalence Principle for the determination of equivalent current densities.

The far-zone radiation field is considered to be the summation of the fields produced by two radiative components in the dielectric rod/conical structure: The "aperture" of the uniform dielectric rod at …

Knowledge Based Designing Of Broadband Coaxial Cable Networks, Tauqir Hameed

Theses

The objective of this research was to build a broadband coaxial cable network. One of the basic requirement of a network is the physical link transmission medium. For the purposes of this research, broadband coaxial cable was chosen as a physical medium of data communication. The approach taken in this research was to divide network design into three main steps. In the first step, the decision on topology of the network was determined. Both Star and Minimum Spanning Tree topologies were used and then the Esau-Williams Algorithm was employed to minimize the cable length. In the second step, various signal …

Composite Stock Cutting Through Simulated Annealing, Pipatpong Poshyanonda, Cihan H. Dagli

Computer Science Technical Reports

This paper explores the use of Simulated Annealing as an optimization technique for the problem Composite Material Stock Cutting. The shapes are not constrained to be convex polygons or even regular shapes. However, due to the composite nature of the material, the orientation of the shapes on the stock is restricted. For placements of various shapes, we show how to determine a cost function, annealing parameters, and performance.

Composite Stock Cutting Through Simulated Annealing, Pipatpong Poshyanonda, Cihan H. Dagli

Computer Science Technical Reports

This paper explores the use of Simulated Annealing as an optimization technique for the problem Composite Material Stock Cutting. The shapes are not constrained to be convex polygons or even regular shapes. However, due to the composite nature of the material, the orientation of the shapes on the stock is restricted. For placements of various shapes, we show how to determine a cost function, annealing parameters, and performance.

Temperature Dependence Of Optical Properties Of Gaas, Huade Yao, Paul G. Snyder, John A. Woollam

Department of Electrical and Computer Engineering: Faculty Publications

Pseudodielectric functions (ε) = (ε₁) + i (ε₂) of GaAs were measured by spectroscopic ellipsometry (SE), in the range of 1.W.45 eV, at temperatures from room temperature (RT) to ~610 ° C. A very clean, smooth surface was obtained by first growing an epitaxial layer of GaAs on a GaAs substrate and immediately capping it with a protective layer of arsenic. The cap prevented surface oxidation during transport to the measurement chamber, where it was evaporated under ultrahigh vacuum at ~350 °C. Room-temperature SE results from this surface are in good agreement with those in the …

Gaseous Component Identification With Polymeric Film Sensor, 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.