Electrical and Computer Engineering Commons^™

Analytical Modeling And Simulation For Investigation Of A Digital Gas Filter Correlation Radiometer, Catherine P. Mcgowan

Electrical & Computer Engineering Theses & Dissertations

This thesis investigates a digital gas filter correlation radiometer called the Tropospheric Radiometer for Atmospheric Chemistry and Environmental Research (TRACER), which will be used to remotely measure carbon monoxide at three levels in the troposphere. The nadir-viewing radiometer measures the differential absorption of radiation through the atmosphere at 4.67@m and 2.33pm wavelengths. This thesis develops an analytical model of the TRACER measurement process to evaluate the effect of varying certain system parameters on the measurement. The independent sampling criterion and the response of linear systems to random signals are explained. A parametric simulation model is also developed to evaluate the …

The Breakdown Mechanism Of Hollow Cathode Discharge, Mai Tuyet Ngo

Electrical & Computer Engineering Theses & Dissertations

In a low pressure discharge, if the cathode incorporates a cylindrical or slit shaped hole, the discharge current can be several orders of magnitude higher than in one with plane parallel electrodes under the same pressure and voltage conditions. In this work hollow cathode discharges in Helium under the influence of variable parameters such as gas pressure, applied voltage, electrode gap spacing, external magnetic field, etc., are investigated by means of electrical and optical diagnostic techniques.

The results indicate that a hollow cathode discharge develops in two stages. The initial breakdown occurs along the longest straight path of the system, …

An Erasable Optical Memory Based On Stimulated Electronic Transition Concept, James D. Satira

Electrical & Computer Engineering Theses & Dissertations

Erasable optical memory systems with a high storage density and a large data transfer rate are required for many real time data acquisition systems such as those placed aboard NASA's space born platforms. A new concept for erasable optical memory involving stimulated electronic transitions (SET) will meet these requirements. The SET concept useful in erasable optical storage systems was demonstrated in MgS and SrS doped with Eu and Sm. The optical properties of these materials were studied. The reading and writing wavelengths for these samples were determined to be 950 and 514 nm respectively. The peaks of the emission spectra …

Signal Processing Methodologies For An Acoustic Fetal Heart Rate Monitor, Robert A. Pretlow Iii

Electrical & Computer Engineering Theses & Dissertations

Research and development is presented of real time signal processing methodologies for the detection of fetal heart tones within a noise-contaminated signal from a passive acoustic sensor. A linear predictor algorithm is utilized for detection of the heart tone event and additional processing derives heart rate. The linear predictor is adaptively "trained" in a least mean square error sense on generic fetal heart tones recorded from patients. A real time monitor system is described which outputs to a strip chart recorder for plotting the time history of the fetal heart rate. The system is validated in the context of the …

Monte Carlo Simulation Of Millimeter-Wave Gunn Effect Oscillators, Ramani Vaidyanathan

Electrical & Computer Engineering Theses & Dissertations

Monte Carlo simulations have been carried out to investigate the performance of microwave Gunn oscillators. Three separate aspects of the simulation problem have been comprehensively addressed in this work. First, the presence of an external circuit has been self-consistently incorporated into the calculations. The inclusion of the external circuit facilitates a study of the circuit controlled regime, and correctly models effects arising from the time dependent boundary conditions. Secondly, microscopic details of the electronic relaxation mechanisms which ultimately control the frequency response limits, have been taken into account through an iterative Monte Carlo-Poisson scheme. This procedure overcomes a potential shortcoming …

An Architecture Level Simulation Methodology, Paul D. Stigall, Ram Huggahalli

Electrical and Computer Engineering Faculty Research & Creative Works

Using the Architecture Design and Assessment System (ADAS), the Processor Level Architecture of an Example Computer System is First Represented as a Directed Graph. Then, a Method of Simulating Instruction Execution as a Sequence of Data Transfers between the Nodes of the Graph is Presented. the Simulation Methodology Provides Flexibility in Observing the Architecture Dynamically at the Processor Level. an Example Application for Functional Verification is Discussed. Development of Techniques to Convert Programs into Node Sequences And, to Assign Appropriate Delays to the Nodes is Necessary to Further Enhance the Applicability of the Methodology. Functional Verification and Performance Estimation through …

Magneto-Optical Kerr Effect And Perpendicular Magnetic Anisotropy Of Evaporated And Sputtered Co/Pt Multilayer Structures, Ping He, William A. Mcgahan, John A. Woollam, F. Sequeda, T. Mcdaniel, H. Do

Department of Electrical and Computer Engineering: Faculty Publications

Thin and ultrathin Co/Pt multilayered structures have been prepared on glass substrates by electron-beam evaporation at room temperature and by sputtering at various substrate temperatures and sputtering pressures. Perpendicular magnetic anisotropy was found in samples with Co/Pt bilayer thicknesses near 3 Å/l0 Å and total thicknesses of the layer stack of no greater than 300 Å. X-ray diffraction was performed on the samples to determine layer spacing and integrity, and possible crystallinity of films. Crystalline structures in the interface between the Co and Pt layers were found and identified. The effects of sputtering parameters, such as pressure and substrate temperature, …

Magnetic-Field Distributions In Zinc-Nickel Ferrite, T. A. Dooling, Desmond C. Cook

Physics Faculty Publications

The Mössbauer effect has been used to study the microscopic magnetic properties of the cubic microwave ferrite (Zn_0.41Ni_0.59)Fe₂O₄ at 300 K. The magnetically split spectrum is broad and unresolved due to the overlap of the hyperfine magnetic fields at the tetrahedral and octahedral sites. This is caused by a distribution of magnetic fields at each site. The distribution is especially large and asymmetric at the octahedral site and is due to the fact that the iron atoms at this site are influenced by the presence of both iron and zinc at the tetrahedral …

Phase Changes In Plasma‐Sprayed Zinc‐Nickel Ferrite, T. A. Dooling, Desmond C. Cook

Physics Faculty Publications

The magnetic and crystalline properties of a plasma‐sprayed coating of the microwave absorbing zinc‐nickel ferrite, (Zn_0.41Ni_0.59 )Fe₂O₄ have been studied at 300 K using the Mössbauer effect and x‐ray diffraction (XRD). Both techniques indicate that the plasma‐sprayed material separated into two phases. The first is a nickel‐rich phase with magnetic fields of 47.5 and 44.5 T at the tetrahedral and octahedral sites, respectively. The second is a zinc‐rich phase, zinc meta‐ferrite, having a small magnetic field of 4.2 T. The quadrupole splitting of this second phase is ΔE=0.34 mm s⁻¹, …

Afit/Afosr Symposium On Applications Of Wavelets To Signal Processing, Volume Ii, Tutorial Notes, Gregory T. Warhola, Mark E. Oxley, Steven K. Rogers, Matthew Kabrisky, Bruce W. Suter

AFIT Documents

The Air Force Institute of Technology (AFIT) hosted the Symposium on Applications of Wavelets to Signal processing during 20-22 March 1991 at the AFIT Science and Research Center, Wright-Patterson AFB, OH. This was the first major academic meeting of its kind held at AFIT. The symposium was sponsored by the Air Force Office of Scientific Research (AFOSR), Bolling AFB, DC. It focused on applications of wavelets to problems in image and speech processing, communications, and graphics and opened with a one-day short course, 'A Tutorial on Wavelets.' The symposium was attended by more than 220 researchers worldwide. They represented 15 …

Modifications To Mcnp, Version 3b: Incorporating A Variable Density Atmosphere. Addendum, David L. Monti, Kirk A. Mathews

AFIT Documents

MCNP version 3B was modified to incorporate a continuously variable density atmosphere. This was accomplished by representing the variation of air density as a function of altitude with a series of continuous piecewise exponential curves up to a maximum altitude of 1000 km. User-written subroutines and functions were written which incorporated these piecewise functions. These subroutines and functions were subsequently incorporated into a production version of MCNP. Several MCNP subroutines and files were modified in support of these modifications. This report discusses detailed information regarding the theoretical development of the variable density model, the user written subroutines and functions, the …

Identifiability In Wind Estimation From Scatterometer Measurements, David G. Long, Jerry M. Mendel

Faculty Publications

The problem of identifiability of a wind vector that is estimated from wind scatterometer measurements of the radar backscatter of the ocean's surface is addressed. The traditional wind estimation approach produces multiple estimates of the wind direction. A second processing step, known as dealiasing or ambiguity removal, is used to select a single wind estimate from these multiple solutions. Dealiasing is typically based on various ad hoc considerations. The traditional wind estimation approach results in multiple solutions associated with local minima in an objective function formed from the noisy backscatter measurements. The authors discuss the question of the uniqueness of …

A Fully Coupled, Automated Formation Control System For Dissimilar Aircraft In Maneuvering Formation Flight, Paul R. Rohs

Theses and Dissertations

This study developed a fully automated formulation control system, capable of controlling a number of like or dissimilar aircraft in maneuvering formation flight. C-130 fixed wing aircraft and H-53 helicopters were modelled in various formulations and simulated through a mix of maneuvers. External formation guidance was assumed as a single data burst of nominal function guidance commands and separation distances for each wing aircraft in the formation. No communication was assumed between formation aircraft. Wing aircraft track lead aircraft maneuvering with an ideal on-board sensor, maneuvering to maintain relative position. It was determined that lead aircraft inputs must be attenuated …

A Navigation Reference System (Nrs) Using Global Positioning System (Gps) Aiding, Richard D. Stacey

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 the output from three major subsystems: inertial navigation system (INS) information, barometric altitude information, and range and range-rate data 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 …

The Synthesis Of Patterns Using A Series-Fed Array Of Annular Sector Radiating Line (Anserlin) Elements: Low-Profile, Circularly Polarized Radiators, James L. Drewniak, P. E. Mayes

Electrical and Computer Engineering Faculty Research & Creative Works

A series-fed, circularly polarized array of annular sector radiating-line elements that operates over a ground plane and has a low profile is presented. Pattern shaping can be achieved through control of the fraction of the incident power that is radiated by each element. This can be accomplished over a wide range by a simple adjustment in the geometry of each element. A synthesis technique is given, and experimental results are presented. The array is demonstrated to have a high return loss (good impedance match) and a low axial ratio

Set-Valued Filtering And Smoothing, Wynn C. Stirling, Darryl Morrell

Faculty Publications

A theory of discrete-time optimal filtering and smoothing based on convex sets of probability distributions is presented. Rather than propagating a single conditional distribution as does conventional Bayesian estimation, a convex set of conditional distributions is evolved. For linear Gaussian systems, the convex set can be generated by a set of Gaussian distributions with equal covariance with means in a convex region of state space. The conventional point-valued Kalman filter is generated to a set-valued Kalman filter consisting of equations of evolution of a convex set of conditional means and a conditional covariance. The resulting estimator is an exact solution …

Convex Bayes Decision Theory, Wynn C. Stirling, Darryl Morrell

Faculty Publications

The basic concepts of Levi's epistemic utility theory and credal convexity are presented. Epistemic utility, in addition to penalizing error as is done with traditional Bayesian decision methodology, permits a unit of informational value to be distributed among the hypotheses of a decision problem. Convex Bayes decision theory retains the conditioning structure of probability-based inference, but addresses many of the objections to Bayesian inference through relaxation of the requirement for numerically definite probabilities. The result is a decision methodology that stresses avoiding errors and seeks decisions that are likely to be highly informative as well as true. By relaxing the …

Quantum Network Theory Of Transport With Application To The Generalized Aharonov-Bohm Effect In Metals And Semiconductors, Cheng-Hsiao Wu, Gunter Mahler

Electrical and Computer Engineering Faculty Research & Creative Works

Quantum transport for resistor networks is developed with a general form factor, where each node point of the network is associated with a potential. The phase factor of the wave function in between two adjacent nodes is related to the reflection coefficient along that path. The exact transmission probability for a generalized Aharonov-Bohm ring is derived for a clean and cold crystal ring of arbitrary two-lead connections. The even- and odd-numbered rings have distinctly different transmission behaviors. The periodicity of the odd-numbered ring with respect to the threaded magnetic flux is shown to be double to that of an even-numbered …

Decomposing Non-Product Form Queueing Lattices Through Autorouting With A* Algorithm, Chun-Chang Yu

Theses

Direct solution techniques are expensive for the state transition lattice of a class of non-product form queuing modes. In this thesis, Autorouting with A* algorithm is adapted to decompose it as solvable subsets which can be solved sequentially and independently. Autorouting with A* algorithm is heuristics in problem solving. It also is one of a class of global optimization problems that are difficult to solve. Some queuing modes of type A will be decomposed in this thesis through Autorouting with A* algorithm.

Direct Schottky Injection Image Sensors, Subramanyam V. Ayyagari

Theses

This thesis describes the analysis and simulations of Direct Schottky Injection (DSI) imagers which have 100% fill factor. Frame transfer (FT) and interline transfer (IT) DSI imager structures have been investigated. Theoretical Poisson solution for the PT and P-NP FT-DSI structures is presented, which closely agrees with simulation results. Simulation for frame transfer FT-DSI imagers has been done in SUPREM III since 1-D effects are more dominant. Single carrier transit time for both the structures were estimated from the electric fields.

Simulations of IT-DSI structures was done using PISCES llb, to get the local electric fields, which define the directionality …

Multiresolution Techniques : Laplacian Pyramid Coding And Its Comparison With Subband Coding, Danmei Chang

Theses

The multiresolution pyramid and related structures have been developed as intermediate representations between the purely frequency domain and purely spatial domain. In this thesis. we discuss two important pyramid structures which are often used in multiresolution representation: Laplacian pyramid and subband coding.

Laplacian pyramid. a typical pyramid structure, is studied in detail. By means of software implementation. we obtain a comprehensive understanding of its features and applications in image representation and data compression. Several modifications of pyramid structure are used to compress the data dynamic range, reduce the computational complexity and improve performance. Performance of the conventional Laplacian pyramid and …

A Machine Vision System With Remote Host, Chieyeon Jason Chen

Theses

The modem plays an important role in data communication using the Public Swiched Telephone Network. In this thesis, the modem function is merged into a low cost machine vision system based on the Motorola 68HC11. Evalation Board The system comprises the intelligent machine vision con- troller and a remotely located host computer, such as an IBM-PC. It, supports extra long distance communication capability so that the controller and the host can be anywhere in the world where then is a telephone line. Because of the limit of a 2100 bps modem, soft ware data compression is implemented here to save …

Artificial Dielectric Polymeric Optical Waveguides, Peng Chen

Theses

Wave propagation in artificial dielectric polymeric optical thin film waveguides is studied. These artificial dielectric films are made of multiple layers either metallic or semiconductor clusters in polymeric matrix. The waveguides are fabricated using the plasma polymerization and vacuumm evaporation deposition method. By analyzing results of these kinds of structures, some important conclusions can be obtained. The artificial dielectric layer in the waveguide center effectively changes the modal distribution in the waveguides. In the case of semiconductor layer, an all optical switch may be realized.

A Multimode Index Detecting Sensor For Use In Plastic Concrete, Qiyu Chen

Theses

This thesis describes a microcomputer-based measuring system using a laser diode source, a fiber optic sensor and a microcomputer DMA interface to test and analyze the entrained percentage of air in concrete.

The principle of refraction and reflection of light in optical fibers is applied to detection of air bubbles. Reflected light intensity signals are detected and transferred through a DMA interface to a laptop computer. Analysis of reflected light intensity produces a measurement of the air content of fresh concrete. Accuracy of the system is evaluated through extensive laboratory and field trials.

Ct Fan Beam Reconstruction With A Non-Stationary Axis-Of-Rotation, Joseph A. Concepcion

Theses

One important aspect for reconstructing an image using Computed Tomography (CT) is that the axis-of-rotation must pivot at the same point on the reconstruction plane as the x-ray source and CT scanner assembly rotates around the imaged object. This pivot point is used as a reference point for backprojecting pixel values to their proper coordinates. Therefore, reconstructing an image with a non-stationary axis-of-rotation would backproject pixel values to wrong coordinate points, since the reference point is non-stationary for every projection angle.

A convolution filtered backprojection algorithm has been derived for correcting images that were acquired with a non-stationary axis-of-rotation using …

Tri-Color Led Display System Using Microcontroller, Costakis A. Constantinou

Theses

A seven-by-forty-eight tricolor LED display panel is designed and built around the 68HC11 MCU.

Four bilateral switching transistors (4066) are used in a Wien bridge configuration to drive each tri-color LED. With this circuitry one is able to drive the tricolor LED symmetrically. An alternative design that uses only two switching transistors is also offered.

A software program was developed to output on the display scrolling and fixed messages. Each message could be displayed in a different color (Red, Green and Yellow) and at a different speed (Slow, Fast, and Medium). The program also includes an editor with insertion and …

Novel Way Of Sub-Carrier Coherent Detection And Clock Recovery In Fiber-Optic Communications, Narayan Gehlot

Theses

We experimentally demonstrate a novel concept for recovery of a Sub-Carrier and Timing Clock in fiber-optic communication systems using a Wavelength Division Multiplexing technique. The idea is to send a low radio frequency (RF) as a reference pilot from the transmitter to the receiver on a separate laser using the principle of Wavelength Division Multiplexing (WDM). This low frequency signal is taken to be a subharmonic of the subcarrier used to carry information and intensity modulate another laser. Such approach will be expected to generate at the receiver a local oscillator in high coherence with the subcarrier.

We show that …

On The Estimation Of New Life Model Of Transformer Insulation Material Under Combined Electrical And Thermal Stress, Chiming Lin

Theses

Results of combined electrical and thermal aging and only thermal aging studies conducted on a 'fish' paper insulation material are presented in this thesis.

The model for aging has been proposed which is essentially the Arrhenius equation with a weighted factor {exp -cg/kT1 to describe the enhanced reaction rate process under combined thermal and electrical stress. A procedure has been described for evaluation of parameters of this new model.

It is seen that life estimates obtained with this model are close enough to the experimental results.

In addition, reliability data were also generated on the same material using electrical noise. …

Hot : A Timing Optimizer For Hierarchical Vlsi Circuits Using The Charge Conservation Delay Model, Yumei Quan

Theses

The primary benefits of VLSI chips are their high speed, small area, and lower power. These performance attributes are dependent on the quality of chip design. As a result, performance can be optimized by proper design decisions. One of the decisions in chip design is the selection of gate delays and/or transistor sizes (channel width of an MOS transistor).

To optimize the performance of VLSI chips, transistor delay models and optimization algorithms are very important since accurate analytical models for signal delay are essential to replace expensive device level simulation and the high efficient algorithms assist designers in developing high …

Comparative Study Of Prediction Gain Based On Neural Network Architecture, Prashant M. Shah

Theses

This thesis describes the Neural Network approach to design predictor using Delta and Generalized Delta Rule. The predictor is designed by supervised training based on the typical sequence of pixel values. Neural Network is used to find the coefficients of the predictor. Both 1-D and 2-D scheme of the pixels as well as linear and non-linear correlations are used to find the coefficients by training. Different combinations of pixels are used to find the "best" combination among the order of the predictor.