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Full-Text Articles in Engineering
Display And Analysis Of Tomographic Reconstructions Of Multiple Synthetic Aperture Ladar (Sal) Images, Bassirou Seck
Display And Analysis Of Tomographic Reconstructions Of Multiple Synthetic Aperture Ladar (Sal) Images, Bassirou Seck
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Synthetic aperture ladar (SAL) is similar to synthetic aperture radar (SAR) in that it can create range/cross-range slant plane images of the illuminated scatters; however, SAL has wavelengths 10,000x smaller than SAR enabling a relatively narrow real aperture, diffraction limited beam widths. The relatively narrow real aperture resolutions allow for multiple slant planes to be created for a single target with reasonable range/aperture combinations. These multiple slant planes can be projected into a single slant plane projections (as in SAR). It can also be displayed as a 3-D image with asymmetric resolutions, diffraction limited in the dimension orthogonal to the …
True-Average Current-Mode Control Of Dc-Dc Power Converters: Analysis, Design, And Characterization, Dalvir K. Saini
True-Average Current-Mode Control Of Dc-Dc Power Converters: Analysis, Design, And Characterization, Dalvir K. Saini
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Energy efficient, wide-bandwidth, and well-regulated dc-dc power converters are in great demand in today's emerging technologies in areas such as medical, communication, aerospace, and automotive industries. In addition to design and selection of the converter components, a robust closed-loop modeling is very essential for reliable power-electronic systems. Two closed-loop control techniques for power converters exist: voltage-mode control and current-mode control. The principles of voltage-mode control have been explored in great depths by researchers over the last two decades. However, the dynamic modeling of current-mode controlled dc-dc power converters has many uncharted areas that needs careful attention. Two main methods exist …
Examination Of Gain Scheduling And Fuzzy Controllers With Hybrid Reachability, Aaron W. Fifarek
Examination Of Gain Scheduling And Fuzzy Controllers With Hybrid Reachability, Aaron W. Fifarek
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Modern aircraft with nonlinear flight envelopes predominately utilize gain scheduled controllers to provide stability of flight. Using gain scheduled control techniques, nonlinear envelopes can be linearized into collections of linear systems that operate under various system dynamics. Linear controllers approximate the nonlinear response over setpoints of operating conditions which allow traditional linear theory to be applied to maintain stability. Techniques to prove linear stability are well understood and realized in control systems, but when controllers are switched, interpolation methods must be used. Interpolation is necessary as gain scheduled systems do not have foundational switching paradigms as part of their realization …
Wideband Doa And Parameter Estimation Of Chirp Sources Using Dcft And Compressive Sensing, Luay A. Al Irkhis
Wideband Doa And Parameter Estimation Of Chirp Sources Using Dcft And Compressive Sensing, Luay A. Al Irkhis
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Direction of Arrival (DoA) estimation of chirp sources has many applications in radar, sonar and medical imaging. This work considers DoA and parameter estimation of wide- band chirp sources by the use of Discrete Chirp Fourier Transform (DCFT), its Compres- sive Sensing formulation (CS-DCFT) and Distributed CS. DCFT is similar to traditional Discrete Fourier Transform (DFT) but with chirp ba- sis and two-dimensional search over chirp rate and chirp frequency. For chirp parame- ters estimation, the proposed Compressive Sensing (CS) formulation uses the parametric DCFT basis to achieve superior estimator performance in polynomial time using Orthog- onal Matching Pursuit (OMP) …
Feed-Forward Compensation Of Non-Minimum Phase Systems, Venkatesh Dudiki
Feed-Forward Compensation Of Non-Minimum Phase Systems, Venkatesh Dudiki
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Due to inherent limitations posed by existence of zeros of a transfer function in the righthalfof the complex plane, known as non-minimum phase zeros, the issue of dealing withsuch zeros is extremely important in control of linear systems. Considerable literatureexists in control theory to try and minimize or eliminate the effect of non-minimum phasezeros. These include pole-zero cancellation, feedforward compensation, among others.These methods are only limited only to stable systems (systems with poles in the left halfof the complex plane); and will fail for systems that are unstable as well as non-minimumphase.This research focuses in designing feedforward compensators for unstable …
Hardware Security And Vlsi Design Optimization, Hao Xue
Hardware Security And Vlsi Design Optimization, Hao Xue
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Microelectronic circuit is ubiquitous component of modern electrical devices. The increasing complexity and professionality of phases in microelectronic supply chain bring more global cooperation to integrated circuit (IC) production. Therefore, providing a secure environment for microelectronic circuit design does not ensure the integrity of the hardware since any participator of IC fabrication has the opportunity to implant a malicious alteration in original IC design. Especially overseas chip-fabrication is a vital potential threat for national defense products. In theory, anyone who has access to fabrication process can tamper with the original design, with the potential to change function, modify parametric properties …
Resonant Gate-Drive Circuits For High-Frequency Power Converters, Hur Jedi
Resonant Gate-Drive Circuits For High-Frequency Power Converters, Hur Jedi
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The development trend of power converters motivates the pursuit with high density, high efficiency, and low cost. Increasing the frequency can improve the power density and lead to small passive elements and a fast dynamic response. Each one of these power converters must be driven by a gate-drive circuit to operate efficiently. Conventional gate-drivers are used up to frequencies of about 5 MHz and suffer from switching losses. Therefore, the development of switch-mode power supplies (SMPS) operating at high frequencies requires high-speed gate drivers. The presented research in this dissertation focuses on analysis, design, and development of new types of …
Thz Sources Based On Er-Doped Gaas Driven At Telecom-Fiber Wavelengths, Andrea Mingardi
Thz Sources Based On Er-Doped Gaas Driven At Telecom-Fiber Wavelengths, Andrea Mingardi
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This dissertation entails the investigation of ultrafast photoconductive (PC) THz sources driven by fiber and semiconductor lasers around λ= 1550-nm to utilize commercial fiber-optic telecom technology. The preferred approach is to use GaAs with a high concentration of erbium, which has performed well when driven with laser sources at both 800 nm wavelength, through intrinsic photoconductivity, and 1550 nm, through extrinsic photoconductivity. Studies in the early 1990s showed that the Er doping level has a solubility limit of ~ 7 × 1017 cm−3 at 580 °C, above which erbium is incorporated into GaAs as ErAs nanoparticles which promote resonant absorption …
Switching Neural Network Systems For Nonlinear Tracking, Manoj Ghimire
Switching Neural Network Systems For Nonlinear Tracking, Manoj Ghimire
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In this thesis, we consider the problem of tracking in complex nonlinear dynamical systems. While the Kalman filter is known to be the mean-squared error optimal tracker under linear dynamics and linear measurements, more sophisticated models and algorithms are required for complex dynamics. Here, we consider switching systems where the dynamical properties vary (''switch modes") over time. For example, the dynamics of a vehicle may switch as it transitions from interstate to urban conditions, human speech dynamics switch as speakers change, and stock market dynamics switch with discrete news events. In this work, we use mode-dependent neural networks to capture …
Chaotic Based Self-Synchronization For Rf Steganography Radar/Communication Waveform, Michael A. Gonnella
Chaotic Based Self-Synchronization For Rf Steganography Radar/Communication Waveform, Michael A. Gonnella
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In this project, we continue previous CSR project entitled RF Steganography based Joint Radar/Communication Waveform Design to develop a bio-inspired secure low probability detection (LPD) radio frequency (RF) waveform that can serve multiple purposes simultaneously. Previously, we have developed an RF steganography based RF waveform to conceal a secure digital communication within a linear frequency modulated (LFM) chirp radar signal. By exploiting novel reduced phase shift keying modulation and variable symbol duration, the new waveform is resistant to time domain analysis, frequency domain analysis and cyclostationary analysis. However, to demodulate the hidden communication message, the intended receiver has to know …
Temperature Robust Longwave Infrared Hyperspectral Change Detection, Nicholas A. Durkee
Temperature Robust Longwave Infrared Hyperspectral Change Detection, Nicholas A. Durkee
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In this thesis, we develop and evaluate change detection algorithms for longwave infrared (LWIR) hyperspectral imagery. Because measured radiance in the LWIR domain depends on unknown surface temperature, care must be taken to prevent false alarms resulting from in-scene temperature differences that appear as material changes. We consider fewer variables. Examples using synthetic and measured data quantify the computational complexity of the proposed methods and demonstrate orders of magnitude reduction in false alarm rates relative to existing methods. Four strategies to mitigate this effect. In the first, pre-processing via traditional temperatureemissivity separation yields approximately temperature-invariant emissivity vectors for use in …