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Articles 1 - 11 of 11
Full-Text Articles in Engineering
Optimized Design Methodology Of Cavity-Backed Microstrip Antennas With Dielectric Overlays, Douglas J. Hermes
Optimized Design Methodology Of Cavity-Backed Microstrip Antennas With Dielectric Overlays, Douglas J. Hermes
Theses and Dissertations
The optimized design methodology implemented in this research employs a design methodology, namely Response Surface Methodology (RSM), that is relatively new to the electromagnetics field. The design methodology used a full factorial designed experiment, a Hybrid Finite Element Method (HFEM) analysis code, a cubic spline empirical model, an Analysis of Variance (ANOVA) test, and a simplex optimization code to successfully measure, predict, analyze, and optimize average antenna gain and antenna input impedance for a cavity backed microstrip antenna with dielectric overlays. Based on HFEM results from the full factorial designed experiment, a cubic spline empirical model successfully predicted average antenna …
Micro-Electromechanical Switches For Micro-Satellite Power Transfer, Glen A. Kading
Micro-Electromechanical Switches For Micro-Satellite Power Transfer, Glen A. Kading
Theses and Dissertations
In the past few years, microelectromechanical systems (MEMS) have emerged as a promising new technology with tremendous application potential. One of the possible implementations of MEMS technology is in the development of micro-satellites. It should be possible to mass-produce micro-satellites at a fraction of the cost of one conventional satellite. In order for satellites to be robust, a method of transferring power to systems must be addressed. As micro-satellites are made with conventional integrated circuit technologies at a very small scale, a means of transferring power on a similar scale will be investigated. This research addresses the issue of the …
A Wire Antenna Designed For Space Wave Radiation Over The Earth Using A Genetic Algorithm, Brian S. Sandlin
A Wire Antenna Designed For Space Wave Radiation Over The Earth Using A Genetic Algorithm, Brian S. Sandlin
Theses and Dissertations
A wire antenna is designed for optimal performance at low elevation angles in the presence of a lossy half-space. A simple genetic algorithm (GA) and GENOCOP III software are each integrated with Numerical Electromagnetics Code Version 4.1 (NEC4.1) to optimize a wire antenna geometry for multiple objectives: power gain, azimuthal symmetry, and input impedance. The performance of the two versions of the integrated GA are compared. Several of the resulting antennas are analyzed, and an antenna is proposed for use in a Remote Intrusion Monitoring System (RIMS). Simulations suggest that the proposed antenna, which is well-matched, offers a significant increase …
Breast Cancer Mass Detection Using Difference Of Gaussians And Pulse Coupled Neural Networks, Donald A. Cournoyer
Breast Cancer Mass Detection Using Difference Of Gaussians And Pulse Coupled Neural Networks, Donald A. Cournoyer
Theses and Dissertations
CAD, serving as a second reader, has been shown to improve the success of radiologists at detecting breast cancer. This thesis will develop a new algorithm to identify masses in mammograms. The system developed for this thesis will be capable of assisting a radiologist in making decisions.
Effects Of Near-Field Scatterers On Space-Time Adaptive Processing, Jonathan W. Fitton
Effects Of Near-Field Scatterers On Space-Time Adaptive Processing, Jonathan W. Fitton
Theses and Dissertations
Near-field scatterers, such as the wing of an airplane, can affect the ability of the processor to null out clutter and jammer signals. The target, clutter, and jammer signals will reflect off the near-field scatterers into the array and appear to be coming from a direction different from their true sources. This thesis develops a theoretical model for the direct path and scattered path signals from the target, clutter, and jamming signals. The optimum weight vector, normally computed using the steering vector to the target and the covariance matrix of the undesired signals, must now include the effects of the …
Microelectromechanical Scanner Using A Vertical Cavity Surface Emitting Laser, Joseph G. Bouchard Jr.
Microelectromechanical Scanner Using A Vertical Cavity Surface Emitting Laser, Joseph G. Bouchard Jr.
Theses and Dissertations
Optical scanners play a prominent role in the commercial and military industries. The scanner's size, cost and reliability are critical characteristics. In this research a microoptical scanning system was fabricated by incorporating a vertical cavity surface emitting laser (VCSEL) onto a surface machined microelectromechanical die. The micro optics for laser beam steering includes a 135 deg mirror, a Fresnel lens, a lateral scanning rotating mirror, and a vertical scanning fan mirror. The VCSEL was attached to the die by solder and electrical connection was provided by wire bonding. Based on far field measurements the scanner had a lateral scan angle …
Multiple Model Adaptive Estimation And Control Redistribution Performance On The Vista F-16 During Partial Actuator Impairments, Curtis S. Clark
Multiple Model Adaptive Estimation And Control Redistribution Performance On The Vista F-16 During Partial Actuator Impairments, Curtis S. Clark
Theses and Dissertations
Multiple Model Adaptive Estimation with Control Reconfiguration (MMAE/CR) capability to estimate and compensate for partial actuator failures, or "impairments" is investigated using the high-fidelity, nonlinear, six-degree-of-freedom, VISTA F-16 simulation which currently resides on the Simulation Rapid-Prototyping Facility (SRF). After developing a model for inserting partial actuator impairments into the VISTA F-16 truth model, research begins with a battery of single actuator impairment tests. This stage of research explores the capability of the existing MMAE algorithm to estimate single, partial actuator impairments, and helps to define refinements and expansions needed in the MMAE algorithm for the second phase of research: the …
A Single Chip Low Power Implementation Of An Asynchronous Fft Algorithm For Space Applications, Bruce W. Hunt
A Single Chip Low Power Implementation Of An Asynchronous Fft Algorithm For Space Applications, Bruce W. Hunt
Theses and Dissertations
A fully asynchronous fixed point FFT processor is introduced for low power space applications. The architecture is based on an algorithm developed by Suter and Stevens specifically for a low power implementation. The novelty of this architecture lies in its high localization of components and pipelining with no need to share a global memory. High throughput is attained using large numbers of small, local components working in parallel. A derivation of the algorithm from the discrete Fourier transform is presented followed by a discussion of circuit design parameters specifically, those relevant to space applications. The generic architecture is explained with …
Atmospheric Turbulence Scintillation Effects On Wavefront Tilt Estimation, James A. Louthain
Atmospheric Turbulence Scintillation Effects On Wavefront Tilt Estimation, James A. Louthain
Theses and Dissertations
A new atmospheric turbulence screen generator is developed for use in performance calculations of adaptive optics systems valid over a wide range of atmospheric turbulence parameters. The screen generator accounts for diffraction effects caused by weak turbulence and incorporates the phase, amplitude, and cross statistics of the perturbed optical field. The wavefront's phase and amplitude perturbations are taken from the correlation functions developed by Lee and Harp and the cross correlation of the phase and amplitude derived in this thesis. The screen generator uses a modal representation to perform a Fourier series expansion of the wavefront phase and amplitude over …
Evaluation Of A Maximum A-Posteriori Slope Estimator For A Hartmann Wavefront Sensor, Troy B. Van Caster
Evaluation Of A Maximum A-Posteriori Slope Estimator For A Hartmann Wavefront Sensor, Troy B. Van Caster
Theses and Dissertations
Current methods for estimating the wavefront slope at the aperture of a telescope using a Hartmann wavefront sensor are based upon a centroid shift estimator. The centroid shift estimator determines the displacement, or shift, of the centroid off the optical axis using a moment calculation of the intensity distributions recorded in each subaperture. This centroid shift is proportional to the average slope of the wavefront in each subaperture. A maximum a-posteriori (MAP) slope estimator takes advantage of a-priori knowledge of the wavefront slope statistics and total irradiance falling on the subaperture detector arrays when determining the shift estimate. In order …
Secondary Data Support And Non-Homogeneities In Space-Time Adaptive Processing, Todd B. Hale
Secondary Data Support And Non-Homogeneities In Space-Time Adaptive Processing, Todd B. Hale
Theses and Dissertations
One of the primary problems with the application of Space-Time Adaptive Processing (STAP) techniques is secondary data support for the interference plus noise covariance matrix estimate. Reed has shown the required secondary data support to achieve performance within 3 dB of optimal SINR is approximately equal to twice the degrees of freedom (DOF) used in the algorithm. Reed proved this rule for Sample Matrix Inversion (SMI) techniques. A concern arises when applying this rule to a newer class of reduced dimension STAP algorithms that do not fall under the SMI umbrella. This thesis focuses on the Cross Spectral Metric (CSM) …