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Articles 1 - 30 of 32
Full-Text Articles in Engineering
A Multi-Objective No-Regret Decision Making Model With Bayesian Learning For Autonomous Unmanned Systems, Matthew Howard
A Multi-Objective No-Regret Decision Making Model With Bayesian Learning For Autonomous Unmanned Systems, Matthew Howard
Electronic Theses and Dissertations
The development of a multi-objective decision making and learning model for the use in unmanned systems is the focus of this project. Starting with traditional game theory and psychological learning theories developed in the past, a new model for machine learning is developed. This model incorporates a no-regret decision making model with a Bayesian learning process which has the ability to adapt to errors found in preconceived costs associated with each objective. This learning ability is what sets this model apart from many others. By creating a model based on previously developed human learning models, hundreds of years of experience …
Reducing Eddy Currents In High Magnetic Field Environments, Russell Case
Reducing Eddy Currents In High Magnetic Field Environments, Russell Case
Electronic Theses and Dissertations
When an electrical conducting volume is placed into the bore of an MRI undergoing an image scan, time varying magnetic gradients induce eddy currents in this conducting material. These eddy currents in turn produce a mechanical torque on this volume. It is the goal of this thesis to produce a computer simulation of eddy currents produced by placing conducting materials inside an MRI bore. The first part of the thesis establishes the physics and principles behind an MRI system along with several applications. Next, this thesis presents an analysis of eddy current effects produced on a conductor placed into an …
Comparison Of Theoretical Models Of Power Spectral Density To The Experimental Value For Spectrum Of Irradiance Fluctuations, Craig Hershberger
Comparison Of Theoretical Models Of Power Spectral Density To The Experimental Value For Spectrum Of Irradiance Fluctuations, Craig Hershberger
Electronic Theses and Dissertations
A propagation experiment was designed, assembled, and conducted on an extended range to verify theoretical temporal models for weak to strong fluctuation theory. Laser light intensity was propagated over terrain at the Kennedy Space Center (Florida), and detected using optical receivers at a distance of 13.3 Km from the optical source. The intensity data from the experiment was used to generate an experimental Power Spectral Density (PSD) function. The theoretical Mutual Coherence Function (MCF) and Wave Structure Function (WSF) as set forth by Andrews/Phillips , were evaluated to determine the effective relationship between the statistical moments of the random optical …
Bi-Directional Dcm Dc-To-Dc Converter For Hybrid Electric Vehicles, Michael Pepper
Bi-Directional Dcm Dc-To-Dc Converter For Hybrid Electric Vehicles, Michael Pepper
Electronic Theses and Dissertations
With the recent revival of the hybrid vehicle much advancement in power management has been made. The most popular hybrid vehicle, the hybrid electric vehicle, has many topologies developed to realize this hybrid vehicle. From these topologies, as sub set was created to define a particular group of vehicles where the converter discussed in this thesis has the most advantage. This sub set is defined by two electric sources of power coupled together at a common bus. This set up presents many unique operating conditions which can be handled seamlessly by the DC-to-DC converter when designed properly. The DC-to-DC converter …
A Time-Varying Radiometric Bias Correction For The Trmm Microwave Imager, Kaushik Gopalan
A Time-Varying Radiometric Bias Correction For The Trmm Microwave Imager, Kaushik Gopalan
Electronic Theses and Dissertations
This dissertation provides a robust radiometric calibration for the TRMM Microwave Imager to correct systematic brightness temperature errors, which vary dynamically with orbit position (time) and day of the year. The presence of a time-varying bias in TMI is confirmed by inter-calibration with WindSat and SSMI. This time varying bias is manifested as a time of day dependent variation of the relative biases between TMI and both WindSat and SSMI. In this dissertation, we provide convincing evidence that this time-varying Tb bias in TMI is caused by variations in the physical temperature of the emissive TMI reflector antenna. This dissertation …
Design, Characterization And Compact Modeling Of Novel Silicon Controlled Rectifier (Scr)-Based Devices For Electrostatic Discha, Lifang Lou
Electronic Theses and Dissertations
Electrostatic Discharge (ESD), an event of a sudden transfer of electrons between two bodies at different potentials, happens commonly throughout nature. When such even occurs on integrated circuits (ICs), ICs will be damaged and failures result. As the evolution of semiconductor technologies, increasing usage of automated equipments and the emerging of more and more complex circuit applications, ICs are more sensitive to ESD strikes. Main ESD events occurring in semiconductor industry have been standardized as human body model (HBM), machine model (MM), charged device model (CDM) and international electrotechnical commission model (IEC) for control, monitor and test. In additional to …
Transient Response Improvement For Multi-Phase Voltage Regulators, Shangyang Xiao
Transient Response Improvement For Multi-Phase Voltage Regulators, Shangyang Xiao
Electronic Theses and Dissertations
Next generation microprocessor (Vcore) requirements for high current slew rates and fast transient response together with low output voltage have posed great challenges on voltage regulator (VR) design . Since the debut of Intel 80X86 series, CPUs have greatly improved in performance with a dramatic increase on power consumption. According to the latest Intel VR11 design guidelines , the operational current may ramp up to 140A with typical voltages in the 1.1V to 1.4V range, while the slew rate of the transient current can be as high as 1.9A/ns [1, 2]. Meanwhile, the transient-response requirements are becoming stringer and stringer. …
Design Of Polynomial-Based Filters For Continuously Variable Sample Rate Conversion With Applications In Synthetic Instrumentati, Matthew Hunter
Design Of Polynomial-Based Filters For Continuously Variable Sample Rate Conversion With Applications In Synthetic Instrumentati, Matthew Hunter
Electronic Theses and Dissertations
In this work, the design and application of Polynomial-Based Filters (PBF) for continuously variable Sample Rate Conversion (SRC) is studied. The major contributions of this work are summarized as follows. First, an explicit formula for the Fourier Transform of both a symmetrical and nonsymmetrical PBF impulse response with variable basis function coefficients is derived. In the literature only one explicit formula is given, and that for a symmetrical even length filter with fixed basis function coefficients. The frequency domain optimization of PBFs via linear programming has been proposed in the literature, however, the algorithm was not detailed nor were explicit …
Optical Solitons In Periodic Structures, Konstantinos Makris
Optical Solitons In Periodic Structures, Konstantinos Makris
Electronic Theses and Dissertations
By nature discrete solitons represent self-trapped wavepackets in nonlinear periodic structures and result from the interplay between lattice diffraction (or dispersion) and material nonlinearity. In optics, this class of self-localized states has been successfully observed in both one-and two-dimensional nonlinear waveguide arrays. In recent years such lattice structures have been implemented or induced in a variety of material systems including those with cubic (Kerr), quadratic, photorefractive, and liquid-crystal nonlinearities. In all cases the underlying periodicity or discreteness leads to new families of optical solitons that have no counterpart whatsoever in continuous systems. In the first part of this dissertation, a …
High Power Mode-Locked Semiconductor Lasers And Their Applications, Shinwook Lee
High Power Mode-Locked Semiconductor Lasers And Their Applications, Shinwook Lee
Electronic Theses and Dissertations
In this dissertation, a novel semiconductor mode-locked oscillator which is an extension of eXtreme Chirped Pulse Amplification (XCPA) is investigated. An eXtreme Chirped Pulse Oscillator (XCPO) implemented with a Theta cavity also based on a semiconductor gain is presented for generating more than 30ns frequency-swept pulses with more than 100pJ of pulse energy and 3.6ps compressed pulses directly from the oscillator. The XCPO shows the two distinct characteristics which are the scalability of the output energy and the mode-locked spectrum with respect to repetition rate. The laser cavity design allows for low repetition rate operation < 100MHz. The cavity significantly reduces nonlinear carrier dynamics, integrated self phase modulation (SPM), and fast gain recovery in a Semiconductor optical Amplifier (SOA). Secondly, a functional device, called a Grating Coupled Surface Emitting Laser (GCSEL) is investigated. For the first time, passive and hybrid mode-locking of a GCSEL is achieved by using saturable absorption in the passive section of GCSEL. To verify the present limitation of the GCSEL for passive and hybrid mode-locking, a dispersion matched cavity is explored. In addition, a Grating Coupled surface emitting Semiconductor Optical Amplifier (GCSOA) is also investigated to achieve high energy pulse. An energy extraction experiment for GCSOA using stretched pulses generated from the colliding pulse semiconductor mode-locked laser via a chirped fiber bragg grating, which exploits the XCPA advantages is also demonstrated. Finally, passive optical cavity amplification using an enhancement cavity is presented. In order to achieve the interferometric stability, the Hänsch-Couillaud Method is employed to stabilize the passive optical cavity. The astigmatism-free optical cavity employing an acousto-optic modulator (AOM) is designed and demonstrated. In the passive optical cavity, a 7.2 of amplification factor is achieved with a 50 KHz dumping rate.
Ultrashort Laser Pulse Interaction With Photo-Thermo-Refractive Glass, Leo Siiman
Ultrashort Laser Pulse Interaction With Photo-Thermo-Refractive Glass, Leo Siiman
Electronic Theses and Dissertations
Photo-thermo-refractive (PTR) glass is an ideal photosensitive material for recording phase volume holograms. It is a homogeneous multi-component silicate glass that demonstrates all the advantages of optical glass: thermal stability, high laser damage threshold, and a wide transparency range. Moreover the ability to record phase patterns (i.e. spatial refractive index variations) into PTR glass has resulted in the fabrication of volume holograms with diffraction efficiency greater than 99%. The conventional method of recording a hologram in PTR glass relies on exposure to continuous-wave ultraviolet laser radiation. In this dissertation the interaction between infrared ultrashort laser pulses and PTR glass is …
Cholesteric Liquid Crystal Photonic Crystal Lasers And Photonic Devices, Ying Zhou
Cholesteric Liquid Crystal Photonic Crystal Lasers And Photonic Devices, Ying Zhou
Electronic Theses and Dissertations
This dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser dye, cholesteric liquid crystals provide distributed feedback so that mirrorless lasing is hence possible. Due to the limited surface anchoring, the thickness of gain medium and feedback length is …
Integrated Optical Spr (Surface Plasmon Resonance) Sensor Based On Optoelectronic Platform, Hyungseok Bang
Integrated Optical Spr (Surface Plasmon Resonance) Sensor Based On Optoelectronic Platform, Hyungseok Bang
Electronic Theses and Dissertations
Current major demands in SPR sensor development are system miniaturization and throughput improvement. Structuring an array of integrated optical SPR sensor heads on a semiconductor based optoelectronic platform could be a promising solution for those issues, since integrated optical waveguides have highly miniaturized dimension and the optoelectronic platform enables on-chip optical-to-electrical signal conversion. Utilizing a semiconductor based platform to achieve optoelectronic functionality poses requirements to the senor head; the sensor head needs to have reasonably small size while it should have reasonable sensitivity and fabrication tolerance. This research proposes a novel type of SPR sensor head and demonstrates a fabricated …
Design And Optimization Of Nanostructured Optical Filters, Jeremiah Brown
Design And Optimization Of Nanostructured Optical Filters, Jeremiah Brown
Electronic Theses and Dissertations
Optical filters encompass a vast array of devices and structures for a wide variety of applications. Generally speaking, an optical filter is some structure that applies a designed amplitude and phase transform to an incident signal. Different classes of filters have vastly divergent characteristics, and one of the challenges in the optical design process is identifying the ideal filter for a given application and optimizing it to obtain a specific response. In particular, it is highly advantageous to obtain a filter that can be seamlessly integrated into an overall device package without requiring exotic fabrication steps, extremely sensitive alignments, or …
Digital Signal Processing Techniques For Coherent Optical Communication, Gilad Goldfarb
Digital Signal Processing Techniques For Coherent Optical Communication, Gilad Goldfarb
Electronic Theses and Dissertations
Coherent detection with subsequent digital signal processing (DSP) is developed, analyzed theoretically and numerically and experimentally demonstrated in various fiber-optic transmission scenarios. The use of DSP in conjunction with coherent detection unleashes the benefits of coherent detection which rely on the preservation of full information of the incoming field. These benefits include high receiver sensitivity, the ability to achieve high spectral-efficiency and the use of advanced modulation formats. With the immense advancements in DSP speeds, many of the problems hindering the use of coherent detection in optical transmission systems have been eliminated. Most notably, DSP alleviates the need for hardware …
Stable Optical Frequency Comb Generation And Applications In Arbitrary Waveform Generation, Signal Processing And Optical Data M, Sarper Ozharar
Stable Optical Frequency Comb Generation And Applications In Arbitrary Waveform Generation, Signal Processing And Optical Data M, Sarper Ozharar
Electronic Theses and Dissertations
This thesis focuses on the generation and applications of stable optical frequency combs. Optical frequency combs are defined as equally spaced optical frequencies with a fixed phase relation among themselves. The conventional source of optical frequency combs is the optical spectrum of the modelocked lasers. In this work, we investigated alternative methods for optical comb generation, such as dual sine wave phase modulation, which is more practical and cost effective compared to modelocked lasers stabilized to a reference. Incorporating these comblines, we have generated tunable RF tones using the serrodyne technique. The tuning range was ±1 MHz, limited by the …
Extended Focus Range High Resolution Endoscopic Optical Coherence Tomography, Kye-Sung Lee
Extended Focus Range High Resolution Endoscopic Optical Coherence Tomography, Kye-Sung Lee
Electronic Theses and Dissertations
Today, medical imaging is playing an important role in medicine as it provides the techniques and processes used to create images of the human body or parts thereof for clinical purposes (medical procedures seeking to reveal, diagnose or examine disease) or medical science (including the study of normal anatomy and function). Modalities are developing over time to achieve the highest possible resolution, speed of image acquisition, sensitivity, and specificity. In the past decade, advances in optics, fiber, as well as laser technology have enabled the development of noninvasive optical biomedical imaging technology that can also be applied to endoscopy to …
Meshfree Approximation Methods For Free-Form Optical Surfaces With Applications To Head-Worn Displays, Ozan Cakmakci
Meshfree Approximation Methods For Free-Form Optical Surfaces With Applications To Head-Worn Displays, Ozan Cakmakci
Electronic Theses and Dissertations
Compact and lightweight optical designs achieving acceptable image quality, field of view, eye clearance, eyebox size, operating across the visible spectrum, are the key to the success of next generation head-worn displays. The first part of this thesis reports on the design, fabrication, and analysis of off-axis magnifier designs. The first design is catadioptric and consists of two elements. The lens utilizes a diffractive optical element and the mirror has a free-form surface described with an x-y polynomial. A comparison of color correction between doublets and single layer diffractive optical elements in an eyepiece as a function of eye clearance …
High Temperature Packaging For Wide Bandgap Semiconductor Devices, Brian Grummel
High Temperature Packaging For Wide Bandgap Semiconductor Devices, Brian Grummel
Electronic Theses and Dissertations
Currently, wide bandgap semiconductor devices feature increased efficiency, higher current handling capabilities, and higher reverse blocking voltages than silicon devices while recent fabrication advances have them drawing near to the marketplace. However these new semiconductors are in need of new packaging that will allow for their application in several important uses including hybrid electrical vehicles, new and existing energy sources, and increased efficiency in multiple new and existing technologies. Also, current power module designs for silicon devices are rife with problems that must be enhanced to improve reliability. This thesis introduces new packaging that is thermally resilient and has reduced …
A Low Phase Noise K-Band Oscillator Utilizing An Embedded Dielectric Resonator On Multilayer High Frequency Laminates, Ajay Subramanian
A Low Phase Noise K-Band Oscillator Utilizing An Embedded Dielectric Resonator On Multilayer High Frequency Laminates, Ajay Subramanian
Electronic Theses and Dissertations
K-Band (18 to 26 GHz) dielectric resonator oscillators are typically used as a local oscillator in most K-Band digital transmitter/receiver topologies. Traditionally, the oscillator itself is made up of an active device, a dielectric resonator termination network, and a passive load matching network. The termination network embodies a cylindrical high permittivity dielectric resonator that is coupled on the same plane as a current carrying transmission line. This configuration provides an adequate resonance needed for oscillation but has some limitations. In order to provide a high Q resonance the entire oscillator is placed in a metal box to prevent radiation losses. …
Effects Of Source Water Blending Following Treatment With Sodium Silicate As A Corrosion Inhibitor On Metal Release Within A Wat, Phillip Lintereur
Effects Of Source Water Blending Following Treatment With Sodium Silicate As A Corrosion Inhibitor On Metal Release Within A Wat, Phillip Lintereur
Electronic Theses and Dissertations
A study was conducted to investigate and quantify the effects of corrosion inhibitors on metal release within a pilot distribution system while varying the source water. The pilot distribution system consisted of pre-existing facilities from Taylor et al (2005). Iron, copper, and lead release data were collected during four separate phases of operation. Each phase was characterized by the particular blend ratios used during the study. A blended source water represented a water that had been derived from a consistent proportion of three different source waters. These source waters included (1) surface water treated through enhanced coagulation/sedimentation/filtration, (2) conventionally treated …
Ultra-Wide Band In Communications: Performance Analysis And Enhancements, Burak Berksoy
Ultra-Wide Band In Communications: Performance Analysis And Enhancements, Burak Berksoy
Electronic Theses and Dissertations
Over the last ten years, Ultra-Wide Band (UWB) technology has attracted tremendous research attention. Frequency allocation of 3.1-10.6 GHz for UWB application by FCC made it apparent that UWB will be the technology for future wireless high speed communication applications. With the promise of high data rates (high channel capacity), UWB also offers advantages such as communication security, high multi-path resolution, good penetration capability, ability to coexist with other communication schemes in the same band, and finally, circuit simplicity. The theoretical advantages of UWB has made it a great candidate for short distance communications, however, UWB communications have many challenges, …
Inter-Satellite Microwave Radiometer Calibration, Liang Hong
Inter-Satellite Microwave Radiometer Calibration, Liang Hong
Electronic Theses and Dissertations
The removal of systematic brightness temperature (Tb) biases is necessary when producing decadal passive microwave data sets for weather and climate research. It is crucial to achieve Tb measurement consistency among all satellites in a constellation as well as to maintain sustained calibration accuracy over the lifetime of each satellite sensor. In-orbit inter-satellite radiometric calibration techniques provide a long term, group-wise solution; however, since radiometers operate at different frequencies and viewing angles, Tb normalizations are made before making intermediate comparisons of their near-simultaneous measurements. In this dissertation, a new approach is investigated to perform these normalizations from one satellite's measurements …
Phase And Amplitude Modulated Ofdm For Dispersion Managed Wdm Systems, Andreas Eisele
Phase And Amplitude Modulated Ofdm For Dispersion Managed Wdm Systems, Andreas Eisele
Electronic Theses and Dissertations
Amplitude and phase modulated optical OFDM (Orthogonal Frequency Division Multiplexing) are analyzed in a 50GBit/s single channel and 40GBit/s 5 channel 512 subcarrier non-ideal dispersion-compensated fiber optic communication systems. PM-OFDM is investigated as an alternative to AM-OFDM to alleviate the problem associated with amplitude-modulated signals in a nonlinear medium. The inherent dispersion compensation capability in OFDM (using a cyclic prefix) allows transmission over a link whose dispersion map is not exactly known. OFDM also mitigates the effects of dispersion slope in wavelength-division multiplexed (WDM) systems. Moreover, the overall dispersion throughout the transmission link may vary due to environmental effects and …
Low Noise, High Repetition Rate Semiconductor-Based Mode-Locked Lasers For Signal Processing And Coherent Communications, Franklyn Quinlan
Low Noise, High Repetition Rate Semiconductor-Based Mode-Locked Lasers For Signal Processing And Coherent Communications, Franklyn Quinlan
Electronic Theses and Dissertations
This dissertation details work on high repetition rate semiconductor mode-locked lasers. The qualities of stable pulse trains and stable optical frequency content are the focus of the work performed. First, applications of such lasers are reviewed with particular attention to applications only realizable with laser performance such as presented in this dissertation. Sources of timing jitter are also reviewed, as are techniques by which the timing jitter of a 10 GHz optical pulse train may be measured. Experimental results begin with an exploration of the consequences on the timing and amplitude jitter of the phase noise of an RF source …
Audio And Video Tempo Analysis For Dance Detection, Ryan Faircloth
Audio And Video Tempo Analysis For Dance Detection, Ryan Faircloth
Electronic Theses and Dissertations
The amount of multimedia in existence has become so extensive that the organization of this data cannot be performed manually. Systems designed to maintain such quantity need superior methods of understanding the information contained in the data. Aspects of Computer Vision deal with such problems for the understanding of image and video content. Additionally large ontologies such as LSCOM are collections of feasible high-level concepts that are of interest to identify within multimedia content. While ontologies often include the activity of dance it has had virtually no coverage in Computer Vision literature in terms of actual detection. We will demonstrate …
Data Communication With A Nano-Satellite Using Satellite Personal Communication Networks (S-Pcns), Khudeja Khan
Data Communication With A Nano-Satellite Using Satellite Personal Communication Networks (S-Pcns), Khudeja Khan
Electronic Theses and Dissertations
Satellites typically communicate with locations on the ground to receive commands and send data back. Establishing reliable communications generally requires dedicated ground stations, which in turn require hardware and expertise. Developers of nano-satellites, however, may not have the expertise or resources necessary for establishing a dedicated ground station. Therefore, the use of an existing communication system, such as the Satellite Personal Communication Networks (S-PCNs), is attractive. Another shortcoming of the fixed ground stations, already available, is that they are normally only able to communicate with Low Earth Orbit (LEO) nano-satellites four times per day (two10-minute windows separated by 90 minutes, …
Numerical Modeling Of Wave Propagation In Nonlinear Photonic Crystal Fiber, Md. Kaisar Khan
Numerical Modeling Of Wave Propagation In Nonlinear Photonic Crystal Fiber, Md. Kaisar Khan
Electronic Theses and Dissertations
In this dissertation, we propose numerical techniques to explain physical phenomenon of nonlinear photonic crystal fiber (PCF). We explain novel physical effects occurred in PCF subjected to very short duration pulses including soliton. To overcome the limitations in the analytical formulation for PCF, an accurate and efficient numerical analysis is required to explain both linear and nonlinear physical characteristics. A vector finite element based model was developed to precisely synthesize the guided modes in order to evaluate coupling coefficients, nonlinear coefficient and higher order dispersions of PCFs. This finite element model (FEM) is capable of evaluating coupling length of directional …
Modeling And Analysis Of Power Mosfets For High Frequency Dc-Dc Converters, Yali Xiong
Modeling And Analysis Of Power Mosfets For High Frequency Dc-Dc Converters, Yali Xiong
Electronic Theses and Dissertations
Evolutions in integrated circuit technology require the use of a high-frequency synchronous buck converter in order to achieve low cost, low profile, fast transient response and high power density. However, high frequency operation leads to increased power MOSFET switching losses. Optimization of the MOSFETs plays an important role in improving converter performance. This dissertation focuses on revealing the power loss mechanism of power MOSFETs and the relationship between power MOSFET structure and its power loss. The analytical device model, combined with circuit modeling, cannot reveal the relationship between device structure and its power loss due to the highly non-linear characteristics …
Real-Time Trajectory Planning For Groundand Aerial Vehicles In A Dynamic Environment, Jian Yang
Real-Time Trajectory Planning For Groundand Aerial Vehicles In A Dynamic Environment, Jian Yang
Electronic Theses and Dissertations
In this dissertation, a novel and generic solution of trajectory generation is developed and evaluated for ground and aerial vehicles in a dynamic environment. By explicitly considering a kinematic model of the ground vehicles, the family of feasible trajectories and their corresponding steering controls are derived in a closed form and are expressed in terms of one adjustable parameter for the purpose of collision avoidance. A collision-avoidance condition is developed for the dynamically changing environment, which consists of a time criterion and a geometrical criterion. By imposing this condition, one can determine a family of collision-free paths in a closed …