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Articles 1 - 18 of 18
Full-Text Articles in Engineering
An Invariance Transformation Algorithm For Defect Characterization Of Ultrasonic Signals For The Nondestructive Evaluation Of Concrete, Michael Dominic Ciocco
An Invariance Transformation Algorithm For Defect Characterization Of Ultrasonic Signals For The Nondestructive Evaluation Of Concrete, Michael Dominic Ciocco
Theses and Dissertations
Nondestructive evaluation (NDE) techniques offer cost-effective strategies for monitoring the integrity of a variety of civil infrastructure, such as natural gas and sewer pipelines, without the need to take the system off-line. However, interpretation of NDE signals in terms of the location, size, and shape of underlying flaws in the material being inspected is fraught with difficulty. Typically, variations in the testing signal due to operational parameters have created a significant challenge for defect characterization. This thesis proposes, develops, and validates a defect characterization algorithm that compensates for operational variables and maps the test signal to a visual defect profile. …
Automated Segmentation Of Radiodense Tissue In Digitized Mammograms Using A Constrained Neyman-Pearson Classifier, Jeremy Thomas Neyhart
Automated Segmentation Of Radiodense Tissue In Digitized Mammograms Using A Constrained Neyman-Pearson Classifier, Jeremy Thomas Neyhart
Theses and Dissertations
Breast cancer is the second leading cause of cancer related mortality among American women. Mammography screening has emerged as a reliable non-invasive technique for early detection of breast cancer. The radiographic appearance of the female breast consists of radiolucent (dark) regions and radiodense (light) regions due to connective and epithelial tissue. It has been established that the percentage of radiodense tissue in a patient's breast can be used as a marker for predicting breast cancer risk. This thesis presents the design, development and validation of a novel automated algorithm for estimating the percentage of radiodense tissue in a digitized mammogram. …
Electromagnetic Scattering From A Gap In A Magneto-Dielectric Coating On An Infinite Ground Plane, George R. Simpson
Electromagnetic Scattering From A Gap In A Magneto-Dielectric Coating On An Infinite Ground Plane, George R. Simpson
Theses and Dissertations
The electromagnetic scattering from a gap in a magneto-dielectric coating on an infinite ground plane is analyzed. In this context, the gap forms a break only in the magneto-dielectric slab coating while the ground plane is continuous and unbroken. Volume equivalence is used to convert the gap region to one containing unknown volumetric equivalent electric and magnetic currents. The equivalent problem then is one of these currents radiating in the presence of an unbroken grounded magneto-dielectric slab. A Green's function for this geometry is developed consisting of two terms: a direct coupling term and correction term to account for the …
Automatic Target Recognition Classification System Evaluation Methodology, Christopher Brian Bassham
Automatic Target Recognition Classification System Evaluation Methodology, Christopher Brian Bassham
Theses and Dissertations
This dissertation research makes contributions towards the evaluation of developing Automatic Target Recognition (ATR) technologies through the application of decision analysis (DA) techniques. ATR technology development decisions should rely not only on the measures of performance (MOPs) associated with a given ATR classification system (CS), but also on the expected measures of effectiveness (MOEs). The purpose of this research is to improve the decision-makers in the ATR Technology development. A decision analysis framework that allows decision-makers in the ATR community to synthesize the performance measures, costs, and characteristics of each ATR system with the preferences and values of both the …
Airborne Radar Interference Suppression Using Adaptive Three-Dimensional Techniques, Todd B. Hale
Airborne Radar Interference Suppression Using Adaptive Three-Dimensional Techniques, Todd B. Hale
Theses and Dissertations
This research advances adaptive interference suppression techniques for airborne radar, addressing the problem of target detection within severe interference environments characterized by high ground clutter levels, levels, noise jammer infiltration, and strong discrete interferers. Two-dimensional (2D) Space-Time Adaptive Processing (STAP) concepts are extended into three-dimensions (3D) by casting each major 2D STAP research area into a 3D framework. The work first develops an appropriate 3D data model with provisions for range ambiguous clutter returns. Adaptive 3D development begins with two factored approaches, 3D Factored Time-Space (3D-FTS) and Elevation-Joint Domain Localized (Elev-JDL). The 3D adaptive development continues with optimal techniques, i.e., …
Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley
Fabrication Techniques For Iii-V Micro-Opto-Electro-Mechanical Systems, Jeremy A. Raley
Theses and Dissertations
This thesis studies selective etching techniques for the development of AlxGa1-xAs micro-opto-electro-mechanical systems (MOEMS). New MEMS technology based on materials such as AlxGa1-xAs enables the development of micro-systems with embedded active micro-optical devices. Tunable micro-lasers and optical switching based on MOEMS technology will improve future wavelength division multiplexing (WDM) systems. WDM vastly increases the speed of military communications and sensor data processing. From my designs, structures are prepared by molecular beam epitaxy. I design a mask set for studies of crystal plane selectivity. I perform a series of experiments on the selective …
Evaluation And Analysis Of Array Antennas For Passive Coherent Location (Pcl) Systems, Baris Calikoglu
Evaluation And Analysis Of Array Antennas For Passive Coherent Location (Pcl) Systems, Baris Calikoglu
Theses and Dissertations
Passive Coherent Location (PCL) systems use a special form of a radar receiver that exploits the ambient radiation in the environment to detect and track targets. Typical transmissions of opportunity that might be exploited include television and FM radiobroadcasts. PCL implies the use of a non-radar electromagnetic sources of illumination, such as commercial radio or television broadcasts also referred as transmitters of opportunity. The use of such illumination sources means that the receiver needs to process waveforms that are not designed for radar purposes. As a consequence, the receivers for PCL systems must be much more customized than traditional receivers, …
Statistical Error Analysis Of A Doa Estimator For A Pcl System Using The Cramer-Rao Bound Theorem, Kerim Say
Statistical Error Analysis Of A Doa Estimator For A Pcl System Using The Cramer-Rao Bound Theorem, Kerim Say
Theses and Dissertations
Direction of Arrival (DOA) estimation of signals has been a popular research area in Signal Processing. DOA estimation also has a significant role in the object location process of Passive Coherent Location (PCL) systems. PCL systems have been in open literature since 1986 and their applications are not as clearly understood as the DOA estimation problem. However, they are the focus of many current research efforts and show much promise. The purpose of this research is to analyze the DOA estimation errors in a PCL system. The performance of DOA estimators is studied using the Cramer-Rao Bound (CRB) Theorem. The …
Development And Characterization Of An Emergency Communications System Using Near Vertical Incident Skywave Antennas, Richard A. Allnutt
Development And Characterization Of An Emergency Communications System Using Near Vertical Incident Skywave Antennas, Richard A. Allnutt
Theses and Dissertations
The NVIS system characterized in this work was designed to eliminate skip propagation by optimizing the design for contiguous coverage. The NVIS technique involves use of transmission and receiving antennas that create nearly vertical propagation and continuous coverage from the transmitter to a distance of 200 miles. Man portable, very low power transceivers (5 watts maximum) and horizontal dipole antennas five feet above the ground are used in an NVIS communication system for this work. The system is designed for the purpose of supporting communication with emergency workers in areas where other communication is difficult. Digital and analog effectiveness are …
Design And Fabrication Of Micro-Electro-Mechanical Structures For Tunable Micro-Optical Devices, Michael C. Harvey
Design And Fabrication Of Micro-Electro-Mechanical Structures For Tunable Micro-Optical Devices, Michael C. Harvey
Theses and Dissertations
Tunable micro-optical devices are expected to be vital for future military optical communication systems. In this research I seek to optimize the design of a microelectromechanical (MEM) structure integrated with a III-V semiconductor micro-optical device. The resonant frequency of an integrated optical device, consisting of a Fabry-Perot etalon or vertical cavity surface emitting laser (VCSEL), may be tuned by applying an actuation voltage to the MEM Flexure, thereby altering the device's optical cavity length. From my analysis I demonstrate tunable devices compatible with conventional silicon 5V integrated circuit technology. My design for a Fabry-Perot etalon has a theoretical tuning range …
Determination Of The Possible Locations Of The Receiver On A Passive Coherent Location System, Considering The Effects Of The Terrain And The Atmospheric Conditions, Carlos A. Meier
Theses and Dissertations
It has always been an issue for an armed force, or government, to obtain complete radar coverage over an area of interest. Generally, this objective remains unaccomplished due to geographical, technical, and/or operational reasons (meaning topographic obstacles, transmitted power, extreme isolation, hierarchy of objectives, etc.) The fact of having vast areas of territory beyond radar coverage can be decisive in an armed conflict. With the recent resurgence of bistatic radar theory and applications, now in the form of Passive Coherent Location (PCL) systems, using existing signal sources (TC and Radio Stations) it is possible to decrease the blind zones of …
Ambiguity Function Analysis And Direct-Path Signal Filtering Of The Digital Audio Broadcast (Dab) Waveform For Passive Coherent Location (Pcl), Abdulkadir Guner
Ambiguity Function Analysis And Direct-Path Signal Filtering Of The Digital Audio Broadcast (Dab) Waveform For Passive Coherent Location (Pcl), Abdulkadir Guner
Theses and Dissertations
This research presents an ambiguity function analysis of the digital audio broadcast (DAB) waveform and one signal detection approach based on signal space projection techniques that effectively filters the direct-path signal from the receiver target channel. Currently, most Passive Coherent Location (PCL) research efforts are focused and based on frequency modulated (FM) radio broadcasts and analog television (TV) waveforms. One active area of PCL research includes the search for new waveforms of opportunity that can be exploited for PCL applications. As considered for this research, one possible waveform of opportunity is the European digital radio standard DAB. For this research, …
Wavelet Domain Communication System (Wdcs): Packet-Based Wavelet Spectral Estimation And M-Ary Signaling, Marion Jay F. Lee
Wavelet Domain Communication System (Wdcs): Packet-Based Wavelet Spectral Estimation And M-Ary Signaling, Marion Jay F. Lee
Theses and Dissertations
A recently proposed Wavelet Domain Communication System (WDCS) using transform domain processing demonstrated excellent interference avoidance capability under adverse environmental conditions. This work extends previous results by: 1) incorporating a wavelet packet decomposition technique, 2) demonstrating M-Ary signaling capability, and 3) providing increased adaptivity over a larger class of interference signals. The newly proposed packet-based WDCS is modeled and its performance characterized using MATLAB®. In addition, the WDCS response to two scenarios simulating Doppler effects and physical separation of transceivers are obtained. The fundamental metric for analysis and performance evaluation is bit error rate (Pb). Relative to …
The Analysis Of Sophisticated Direction Of Arrival Estimation Methods In Passive Coherent Locators, Ahmet Ozcetin
The Analysis Of Sophisticated Direction Of Arrival Estimation Methods In Passive Coherent Locators, Ahmet Ozcetin
Theses and Dissertations
In passive coherent locators (PCL) systems, noise and the precision of direction of arrival (DOA) estimation are key issues. This thesis addresses the implementation of sophisticated DOA estimation methods, in particular the multiple signal classification (MUSIC) algorithm, the conventional beam forming (CBF) algorithm, and the algebraic constant modulus algorithm (ACMA). The goal is to compare the ACMA to the MUSIC, and CBF algorithms for application to PCL. The results and analysis presented here support the use of constant modulus information, where available, as an important addition to DOA estimation. The ACMA offers many simple solutions to noise and separation related …
An Analysis Of Mutually Dispersive Brown Symbols For Non-Linear Ambiguity Suppression, Matthew J. Papaphotis
An Analysis Of Mutually Dispersive Brown Symbols For Non-Linear Ambiguity Suppression, Matthew J. Papaphotis
Theses and Dissertations
This thesis significantly advances research towards the implementation of optimal Non-linear Ambiguity Suppression (NLS) waveforms by analyzing the Brown theorem. The Brown theorem is reintroduced with the use of simplified linear algebraic notation. A methodology for Brown symbol design and digitization is provided, and the concept of dispersive gain is introduced. Numerical methods are utilized to design, synthesize, and analyze Brown symbol performance. The theoretical performance in compression and dispersion of Brown symbols is demonstrated and is shown to exhibit significant improvement compared to discrete codes. As a result of this research a process is derived for the design of …
Microdot - A Four-Bit Microcontroller Designed For Distributed Low-End Computing In Satellites, Anthony R. Woodcock
Microdot - A Four-Bit Microcontroller Designed For Distributed Low-End Computing In Satellites, Anthony R. Woodcock
Theses and Dissertations
Many satellites are an integrated collection of sensors and actuators that require dedicated real-time control. For single processor systems, additional sensors require an increase in computing power and speed to provide the multi-tasking capability needed to service each sensor. Faster processors cost more and consume more power, which taxes a satellite's power resources and may lead to shorter satellite lifetimes. An alternative design approach is a distributed network of small and low power microcontrollers designed for space that handle the computing requirements of each individual sensor and actuator. The design of microdot, a four-bit microcontroller for distributed low-end computing, is …
Translation And Rotation Invariant Multiscale Image Registration, Jennifer L. Manfra
Translation And Rotation Invariant Multiscale Image Registration, Jennifer L. Manfra
Theses and Dissertations
The most recent research involved registering images in the presence of translations and rotations using one iteration of the redundant discrete wavelet transform. We extend this work by creating a new multiscale transform to register two images with translation or rotation differences, independent of scale differences between the images. Our two-dimensional multiscale transform uses an innovative combination of lowpass filtering and the continuous wavelet transform to mimic the two-dimensional redundant discrete wavelet transform. This allows us to obtain multiple subbands at various scales while maintaining the desirable properties of the redundant discrete wavelet transform. Whereas the discrete wavelet transform produces …
Space Time Adaptive Processing And Clutter Classification Integration And Evaluation, Nathan A. Jensen
Space Time Adaptive Processing And Clutter Classification Integration And Evaluation, Nathan A. Jensen
Theses and Dissertations
Radar is a fundamental technology in today's military and civilian environment, and continuing development of this technology is of utmost importance to maintaining technological advantages this realm. Current radar technologies suffer from jamming and clutter limitations. STAP is a statistical method to remove this noise, however it is extremely computationally intensive, and presents several real time processing hurdles. Clutter Classification is another method to classify the radar returns that are found according to the best fit statistical distribution that the return follows. This research investigation attempts to use this clutter classification technology to aid in the detection of targets by …