Engineering Commons^™

Spice-Based Heat Transport Model For Non-Intrusive Thermal Diagnostic Applications, Michael Stelzer

Electrical & Computer Engineering Theses & Dissertations

Nondestructive material testing and diagnostics play an important role in reliability analysis, component wear-out testing, life-cycle estimates, and safety inspections. Of the several techniques available for nondestructive inspections, thermal analysis has been chosen to be the focus of this thesis research. An equivalence between the system of equations for the heat flow problem, and the variables of circuit theory suggests that an electrical model can be constructed to represent the actual thermal system. This electrical model is constructed based upon a finite difference discretization of the heat flow equation. Using these associations a basic one-dimensional electrical model has been constructed …

Coherent Differential Absorption Lidar For Combined Measurement Of Wind And Trace Atmospheric Gases, Grady James Koch

Electrical & Computer Engineering Theses & Dissertations

A lidar system was developed for making combined range-resolved measurements of wind speed and direction, water vapor concentration, and carbon dioxide concentration in the atmosphere. This lidar combines the coherent Doppler technique for wind detection and the differential absorption lidar (DIAL) technique to provide a multifunctional capability. DIAL and coherent lidars have traditionally been thought of and implemented as separate instruments, but the research reported here has shown a demonstration of combining the coherent and DIAL techniques into a single instrument using solid-state lasers. The lasers used are of Ho:Tm:YLF, which operates at a wavelength of 2 μm. This wavelength …

Mitigation Of Water Vapor Interference For Infrared Polarization-Modulated Gas Filter Correlation Radiometry, David K. Lockwood

Electrical & Computer Engineering Theses & Dissertations

Gas filter correlation radiometry (GFCR) is a high-resolution, high-specificity technique for sensing gaseous species. A variation of absorption spectroscopy, GFCR has a long-proven record on orbital platforms for quantitative measurements of atmospheric constituents, as well as common usage in ground-based sensing applications. PMGFCR (Polarization-modulated GFCR) is a recent refinement of the technique with several advantages over the traditional method, including reducing the number of photodetectors required, increased sensitivity, and elimination of moving parts.

To date, no infrared remote sensors have successfully measured nitric oxide (NO) in vehicle exhaust due to spectral overlap by strong water vapor (H₂O_{v …}

Adaptive Threshold Selection Technique For Denoising In Dithered Quantizers, Samuel Peter Kozaitis, Hemen Goswami

Electrical Engineering and Computer Science Faculty Publications

We described an adaptive denoising method to improve image quality in a wavelet-based image compression process that uses dithered quantization. In our method, the second-order moment of the quantization noise is made independent of the signal by random quantization. Then, the quantization noise is reduced by thresholding wavelet coefficients. We first obtained a fixed threshold using any known technique. Then, a neighborhood is searched for the optimal threshold to optimize some cost function.

Hybrid Evolutionary Computing Model For Mobile Agents Of Wireless Internet Multimedia, William S. Hortos

Electrical Engineering and Computer Science Faculty Publications

The ecosystem is used as an evolutionary paradigm of natural laws for the distributed information retrieval via mobile agents to allow the computational load to be added to server nodes of wireless networks, while reducing the traffic on communication links. Based on the Food Web model, a set of computational rules of natural balance form the outer stage to control the evolution of mobile agents providing multimedia services with a wireless Internet protocol (WIP). The evolutionary model shows how mobile agents should behave with the WIP, in particular, how mobile agents can cooperate, compete and learn from each other, based …

Transient Response Of Passive Matrix Polymer Led Displays, David Braun, K. Erickson, G. Yu

Electrical Engineering

Video displays based on polymer and organic displays require high resolution and high data rates. However, the transient response of passive matrix displays based on polymer and organic light-emitting diodes limits display resolution, image uniformity, and image contrast. We use circuit simulation in order to quantify these consequences. This work analyzes how the transient response depends on display resolution, display geometry, pixel position, and row and column electrode design. We conclude that advanced display designs can achieve uniform images at high resolution and contrast.

Method To Optimize Polymer Film Spin Coating For Polymer Led Displays, M. Cecchi, H. Smith, David Braun

Electrical Engineering

Research and development of displays and image sensors based on semiconducting polymers require design of new polymer materials and evaluation of film properties. Application of statistical methods can expedite process development. Optimizing device performance entails determining the effect of several process parameters, necessitates numerous samples, and may consume more scarce new material than desired. Uniform film thickness, with no voids, pinholes, inhomogeneities, or particulate contamination across the substrate can improve display efficiency and uniformity. After performing and analyzing a two-cubed full-factorial experiment with three replicated center points, this paper concludes that spin velocity and polymer concentration have statistically significant effects …

Adaptive And Reconfigurable Flight Control, Yih Shiun Huang

Theses and Dissertations

An indirect adaptive and reconfigurable flight control system is developed. The three-module controller consists of: (1) a system identification module, (2) a parameter estimate smoother, and (3) a proportional and integral compensator for tracking control. Specifically: (1) The identification of a linear discrete-time control system's open-loop gain is addressed. The classical Kalman filter theory for linear control systems is extended and the control system's state and loop gain are jointly estimated on-line. Explicit formulae for the loop gain's estimate and estimation error covariance are derived. The estimate is unbiased and the predicted covariance is reliable. (2) An adaptive smoother is …

On The Solution Of A Class Of Large Body Problems With Partial Circular Symmetry (Multiple Asymmetries) By Using A Hybrid-Dimensional Finite-Difference Time-Domain (Fdtd) Method, Dean Arakaki, Wenhua Yu, Raj Mittra

Electrical Engineering

This paper presents an efficient method to solve a large body scattering problem, viz. a paraboloid reflector antenna system, with only partial circular symmetry. The asymmetry in the system is introduced by two factors, viz. the microstrip feed and an inhomogeneous radome. The paper presents a novel approach, based on the equivalence and reciprocity principles and the “equivalent” aperture theory, to overcome the asymmetry problem. The technique thereby enables substantial computational efficiencies by analyzing the majority of the three-dimensional (3-D) computational domain in an effective two-dimensional (2-D) simulation, with the remainder being analyzed using a 3-D algorithm.

Study Of Surface Chemical Changes And Erosion Rates For Cv-1144-O Silicone Under Electron Cyclotron Resonance Oxygen Plasma Exposure, Li Yan, Xiang Gao, Corey Bungay, John A. Woollam

Department of Electrical and Computer Engineering: Faculty Publications

CV-1144-O silicone thin films were irradiated in an electron cyclotron resonance oxygen plasma, which is a simulation of the low earth orbital environment. A crude equivalence between this plasma system and the low earth orbital environment was determined by measuring Kapton weight loss in the plasma and comparing to Kapton weight loss in space experiments. Changes in optical properties and erosion rates under ultraviolet light and atomic oxygen radiation were studied using in situ spectroscopic ellipsometry (SE). The erosion rate at the beginning of the plasma exposure was significantly faster than that at later stages. Approximately one third of the …

Optical And Etching Studies Of Native Aluminum Oxide Layers For Use In Microcavity Photonic Devices, William L. Bernhard

Theses and Dissertations

Optical communication and computing systems are required to meet future information transfer and processing needs. Microcavity devices serve as an enabling technology to implement and integrate optoelectronic systems. It is important to understand the optical and mechanical properties of materials utilize within microcavity devices. Only then is it possible to accurately model and analyze structures. Microcavity structures incorporating a high aluminum content AlGaAs layers are designed, grown, processed, and measured. The processing of these devices includes the conversion of high aluminum-content AlGaAs layers to native aluminum oxide (AlO) layers through the process of thermal oxidation. This selective conversion of microcavity …

Image Registration Using Redundant Wavelet Transforms, Richard K. Brown

Theses and Dissertations

Imagery is collected much faster and in significantly greater quantities today compared to a few years ago. Accurate registration of this imagery is vital for comparing the similarities and differences between multiple images. Since human analysis is tedious and error prone for large data sets, we require an automatic, efficient, robust, and accurate method to register images. Wavelet transforms have proven useful for a variety of signal and image processing tasks, including image registration. In our research, we present a fundamentally new wavelet-based registration algorithm utilizing redundant transforms and a masking process to suppress the adverse effects of noise and …

Development And Testing Of A Multiple Filter Approach For Precise Dgps Positioning And Carrier-Phase Ambiguity Resolution, Paul E. Henderson

Theses and Dissertations

The most precise relative positioning obtained using differential GPS depends on accurately determining carrier-phase integer ambiguities. To achieve high precision, many current static and kinematic algorithms use a floating-point solution until enough information becomes available to fix the carrier-phase ambiguities accurately. A mew method is presented that uses a multiple model Kalman filter to resolve the carrier-phase integer ambiguities. This method starts with the floating-point results, yet smoothly and rapidly attains the precision of the correct fixed-integer solution, eliminating the need to decide when to switch from the floating to the fixed-integer solution. This method is based on a theoretically …

Redundant Wavelet-Based Image Restoration Using A Prior Information, Mary K. Marcum

Theses and Dissertations

Reconnaissance missions and satellites collect hundreds of images loaded with valuable information to be utilized by the Air Force. Intelligence operations must analyze these images to extract the information needed to help commanders make important decisions. No matter how obtained, images of this type are often degraded by noise due to disruptions such as atmospheric disturbances, optical system variations, motion, and large distance from the sensor to the source. This noise must be removed effectively to improve the quality of these images and ensure that the information contained in them can be correctly extracted. The Air Force relies on the …

Wavelet-Based Audio Embedding & Audio/Video Compression, Michael J. Mendenhall

Theses and Dissertations

With the decline in military spending, the United States relies heavily on state side support. Communications has never been more important. High-quality audio and video capabilities are a must. Watermarking, traditionally used for copyright protection, is used in a new and exciting way. An efficient wavelet-based watermarking technique embeds audio information into a video signal. Several highly effective compression techniques are applied to compress the resulting audio/video signal in an embedded fashion. This wavelet-based compression algorithm incorporates bit plane coding, first difference coding, and Huffman coding. To demonstrate the potential of this audio embedding audio/video compression system, an audio signal …

Characterization And Validation Of The Gp-3 Experimental Radar System, Benjamin L. Crossley

Theses and Dissertations

The experimental GP-3 radar system was originally designed and built under contract for the Air Force Research Laboratory (AFRL). AFRL sought AFIT's support in characterizing the as delivered' performance of the GP-3. This research effort focused exclusively on software modifications and hardware validations related to the GP-3 post-processing mode. As modified, tested, and validated, the GP-3's post-processing mode is now fully operational. The GP-3 is capable of transmitting and receiving bandlimited (3.5 MHz) waveforms at X-Band frequencies. System characterization tests included, noise performance and frequency response. System noise performance characterization permitted establishment of the receiver 'noise floor' and enabled determination …

Locating Target At High Speed Using Image Decimation Decomposition Processing, Zikuan Chen, Mohammad Rezaul Karim, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

We develop a decimation-decomposition processing technique that consists of judiciously selecting certain decimation-decomposed components of an image and then performing inter-component processing. For a (k_x,k_y)-decimation decomposition, there may be up to k_xk_y decimation-decomposed components. The minimal surviving and maximal non-surviving lengths associated with inter-component processing algorithm allows for clutter suppression. By removing detection redundancies, one can locate the target at high speed. A “where-then-what” model is proposed for target tracking and recognition. It locates the target by-image decimation-decomposition processing first and then recognizes the target in question using a suitable image recognition technique.

A Model To Predict Diffraction Attenuation Resulting From Signal Propagation Over Terrain In Low Earth Orbit Satellite Systems, Peter R. Pollock

Theses and Dissertations

This study focused on multipath communication propagation impairments to the LEOSAT communications channel. Two terrain diffraction models, based on the geometric theory of diffraction (GTD), were developed and applied to the space-to-ground communications channel. These models were used to predict the impact of terrain on the performance of three LEOSAT communication systems with designs based on the Iridium, Globalstar and Orbcomm implementations. The study verified the feasibility of applying models based on the GTD rather than empirical or statistical models, to approximate the effect of propagating signals over terrain. Both models confirm that signal blockage and multipath propagation, due to …

Phugoid Damping Control, Nicolas J. Schindeler

Theses and Dissertations

A novel phugoid damping control design methodology is developed, based on the use of wind axes and a point-mass aircraft model. The state variables are air speed, flight path angle, and heading angle, the control variables are thrust setting, angle of attack, bank angle, and sideslip angle, and the command signals are airspeed, flight path angle, and heading angle or heading rate. All the variables and parameters are nondimensionalized. A multivariable set point controller is developed which consists of: (1) a trim calculation-based nonlinear feed-forward control computer; thus, given a commanded new trim state (air speed, flight path angle, and …

Microdot-A 4-Bit Synchronous Microcontroller For Space Applications, Kirby M. Watson

Theses and Dissertations

Satellites have limited power budgets due to the amount of power collected by the satellite's solar panels. The goal is to have a wide range of functionality, while running off a limited power source. Large microprocessors use large amounts of power to report back temperature and chemical sensor data to ground stations. By using small micro controllers to perform the data collection and minimizing the usage of the larger microprocessors, the satellites will save power. A prototype design of the Microdot 4-bit micro controller for space applications is presented. Requirements for the Microdot, such as microwatt power consumption and 23 …

The Calibration Of Bistatic Radar Cross Section Measurements, Christopher J. Bradley

Theses and Dissertations

Recent advances in signal processing and remote sensing have highlighted the importance of bistatic radar systems for the purposes of environmental monitoring, surveillance, and tracking radar. The calibration of such systems has been problematic-much more so than similar monostatic systems, primarily as a result of the lack of reference objects suitable for calibrating at any given bistatic angle. This research deals with the problems of calibrating full-polarimetric laboratory-environment bistatic radar systems, including the lack of suitable calibration targets and procedures, and operational considerations such as alignment and mounting. Several popular bistatic calibration techniques are classified, evaluated, and comparisons are made …

Using Gps As A Reference System To Hit A Moving Target, Daryl J. Burnette

Theses and Dissertations

The Affordable Moving Surface Target Engagement (AMSTE) project attempts to develop affordable solutions to the precise moving target surface target engagement problem. Up to this point, most of the error analysis performed for the AMSTE project has been at the error variance level, generating root-sum-square (RSS) total errors from error budgets consisting of constant error variances. In reality, the level of error for both Global Positioning System (GPS) positioning and radar targeting systems is highly dependent upon the given situation (such as the distance between sensor and target, the altitude differences, etc.) This research generates a more comprehensive model of …

Broadband Application Of High Impedance Ground Planes, Keven J. Golla

Theses and Dissertations

Electrical conductors have long been the only materials available to antenna designers for reflecting structures. However, recently reported high impedance ground plane (HIGP) structures offer an alternative by creating image currents and reflections, within a limited frequency stop-band, that are in-phase with a source rather than out-of-phase as for a perfect electric conducting (PEC) surface. Also, the high impedance structures suppress surface waves while surface waves propagate on PEC surfaces. This research explores broadband antenna applications for HIGP structures. A broadband surface mount antenna is applied to both a homogeneous narrowband HIGP and a spatially varying broadband HIGP design. Measurements …

An Objective Evaluation Of Four Sar Image Segmentation Algorithms, Jason B. Gregga

Theses and Dissertations

Because of the large number of SAR images the Air Force generates and the dwindling number of available human analysts, automated methods must be developed. A key step towards automated SAR image analysis is image segmentation. There are many segmentation algorithms, but they have not been tested on a common set of images, and there are no standard test methods. This thesis evaluates four SAR image segmentation algorithms by running them on a common set of data and objectively comparing them to each other and to human segmentors. This objective comparison uses a multi-metric a approach with a set of …

A Low Power Application-Specific Integrated Circuit (Asic) Implementation Of Wavelet Transform/Inverse Transform, Daniel N. Harvala

Theses and Dissertations

A unique ASIC was designed implementing the Haar Wavelet transform for image compression/decompression. ASIC operations include performing the Haar wavelet transform on a 512 by 512 square pixel image, preparing the image for transmission by quantizing and thresholding the transformed data, and performing the inverse Haar wavelet transform, returning the original image with only minor degradation. The ASIC is based on an existing four-chip FPGA implementation. Implementing the design using a dedicated ASIC enhances the speed, decreases chip count to a single die, and uses significantly less power compared to the FPGA implementation. A reduction of RAM accesses was realized …

A Study On The Performance Of Matrix Prepared By Tape Cast And Its Molten Carbonate Fuel Cells (Mcfcs), Hua-Xin Lin, Bao-Lian Yi, Li Zhou, Chang-Qing He, Lian-Ying Kong, En-Jun Zhang

Journal of Electrochemistry

The matrix prepared with γ-LiAlO₂ powder and by tape cast displayed higher ability of preventing from gas cross over and lower ohmic polarization. The voltages of the stack (three cells, 122 cm²) stacked with the matrix were 2.02 and 1.78 V at 200 and 246 mA/cm², respectively, and the output power reached 53.4 W. The cell (28 cm ²) voltages were 0.85 and 0.75 V at 200 and 300 mA/cm², respectively, and the output power was about 6.6 W. Compensating the shrinkage of matrix in stacking cells promoted the enhancement of the …

How Can Direct Mthanol Fuel Cell Benefit From Carbonate Media, Lin Zhuang, Yang Wang, Jun-Tao Lu

Journal of Electrochemistry

The kinetics of methanol oxidation and oxygen reduction in 0.5 mol/L K₂CO₃ were compared with those in 0.5 mol/L H₂SO ₄. Experiments revealed that carbonate media could be more beneficial to direct methanol fuel cell(DMFC). Firstly, both electrode reactions show better performance in the carbonate than in the acid; secondly, materials other than noble metals become possible to be used as the anodic and cathodic catalysts; thirdly, the potential dectease caused by methanol crossover could be depressed by using metal oxide catalysts not stable in acid, such as MnO₂.

Synthesis Of Limn2O4-ΔClΔ Cathode Material By Like-Sol-Gel Methode, Zhao-Yong Chen, Yi He, Xing-Quan Liu, Zhi-Jie Li, Zuo-Long Yu

Journal of Electrochemistry

LiMn₂O_4-δCl_δ was synthesized by like sol gel methode, with calculated LiOH·H₂O, Mn(No₃)₂⋅6H₂O and LiCl·H₂O, and made electrochemical test with these compounds as positive materials. Result demostrated that LiMn₂O_4-δCl_δ cathode material has exellent stability and nearly no capacity loss after reaching stability.

Adsorption And Oxidation Of Ethanol On Nm-Pt/Gc Electrode Ii. Eqcm And In-Situ Ftir Spectroscopic Studies In Acid Media, Guo-Liang Chen, Sheng-Pei Chen, Zhi-You Zhou, Chun-Hua Zhen, Shi-Gang Sun

Journal of Electrochemistry

The adsorption and oxidation of ethanol on nm Pt/GC electrode in acid solutions containing 0.1 mol·L ^-1 H₂SO₄ +0.1 mol·L ^-1 CH₃CH₂OH was investigated by using cyclic voltammetry, EQCM and in situ FTIR spectroscopy. The experimental results demonstrated that the oxidation of CH₃CH₂OH is closely relaed to solution acidity and oxygen species on electrode surface; CH₃CH₂OH was oxidized on nm Pt/GC electrode in acidic media via a dual path reaction mechanism, i.e . CH₃CH₂OH may be oxidized into CO₂ through …

The Photoelectrochemistry Of Tio2-Polyaniline Composite Film, Huai-Guo Huang, Zhi-Xin Zheng, Jin Luo, Hong-Ping Zhang, Ling-Ling Wu, Zhong-Hua Lin

Journal of Electrochemistry

A TiO₂ and polyaniline (PANI) composite film was obtained by electrochemical methods. The SEM image of the composite film showed that the PANI film is almost completely covered with TiO₂ efficiency. The spectra of photocurrent for the TiO₂-PANI composite film were different from these of TiO₂ film photosensitized by PANI. The bandgap energy of TiO₂ film on partially oxidized PANI film was determined as 3.0 eV by the threshold energy of photocurrent band for TiO₂. The spectra of photocurrent for partially oxidized PANI film electrode suggested that it has the characteristics of …