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MODELING SATELLITE FORMATIONS IN THE PRESENCE OF PERTURBATIONS
Title
MODELING SATELLITE FORMATIONS IN THE PRESENCE OF PERTURBATIONS.
Creator
Cannaday, Robert, Johnson, Roger, University of Central Florida
Abstract / Description
The potential benefits of autonomous satellite formation flying in such areas as high- resolution remote sensing, and sparse aperture radar, has stimulated interest in modeling the satellite environment for feasibility and simulation studies to help explore and define the technical challenges that must be solved in order to achieve successful autonomous satellite formations. The purpose of this paper is to develop and describe a numerical simulation of the orbital environment including...
Show moreThe potential benefits of autonomous satellite formation flying in such areas as high- resolution remote sensing, and sparse aperture radar, has stimulated interest in modeling the satellite environment for feasibility and simulation studies to help explore and define the technical challenges that must be solved in order to achieve successful autonomous satellite formations. The purpose of this paper is to develop and describe a numerical simulation of the orbital environment including central force field perturbations and atmospheric drag effects which will be a useful analytical tool for investigating issues relating to maintaining satellite formations in low-earth-orbit. Many of the studies done in this area confine their research to circular orbits, with and without perturbation effects. This study will investigate apply orbital dynamic equations to the problem of maintaining satellite formations in both circular and elliptical orbits, with and without the presence of J2 gravity perturbation effects and atmospheric drag. This effort is primarily focused on modeling the orbital mechanics of one and two satellites in the presence of J2 and drag perturbations This effort is being performed as part of a multi-disciplined University of Central Florida KnightSat project, sponsored by the Air Force, to develop a two-satellite formation in the nanosatellite class, for investigating issues related to using formation satellites for remote earth sensing, to develop three-dimensional mapping.
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Date Issued
2005
Identifier
CFE0000898, ucf:46639
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000898
ANALYTIC & NUMERICAL STUDY OF A VORTEX MOTION EQUATION
Title
ANALYTIC & NUMERICAL STUDY OF A VORTEX MOTION EQUATION.
Creator
Bueller, Daniel, Rollins, David, University of Central Florida
Abstract / Description
A nonlinear second order differential equation related to vortex motion is derived. This equation is analyzed using various numerical and analytical techniques including finding approximate solutions using a perturbative approach.
Date Issued
2011
Identifier
CFE0003720, ucf:48802
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003720
Response of Electrified Micro-Jets to Electrohydrodynamic Perturbations
Title
Response of Electrified Micro-Jets to Electrohydrodynamic Perturbations.
Creator
Yang, Weiwei, Deng, Weiwei, Chen, Ruey-Hung, Ilie, Marcel, University of Central Florida
Abstract / Description
The breakup of liquid jets is ubiquitous with rich underpinning physics and widespread applications. The natural breakup of liquid jets originates from small ambient perturbations, which can grow exponentially until the amplitude as large as the jet radius is reached. For unelectrified inviscid jets, surface energy analysis shows that only the axisymmetric perturbation is possibly unstable, and this mode is referred as varicose instability. For electrified jets, the presence of surface charge...
Show moreThe breakup of liquid jets is ubiquitous with rich underpinning physics and widespread applications. The natural breakup of liquid jets originates from small ambient perturbations, which can grow exponentially until the amplitude as large as the jet radius is reached. For unelectrified inviscid jets, surface energy analysis shows that only the axisymmetric perturbation is possibly unstable, and this mode is referred as varicose instability. For electrified jets, the presence of surface charge enables additional unstable modes, among which the most common one is the whipping (or kink) instability that bends and stretches the charged jet that is responsible for the phenomena of electrospinning. A closer examination of the two instabilities suggests that due to mass conservation, the uneven jet stretching from whipping may translate into radial perturbations and trigger varicose instabilities. Although the varicose and whipping instabilities of electrified micro-jets have both been extensively studied separately, there is little attention paid to the combined effect of these two, which may lead to new jet breakup phenomena. This dissertation investigates the dynamic response of electrified jets under transverse electrohydrodynamic (EHD) perturbations which were introduced by exciters driven by alternating voltage of sweeping frequency. Three different jetting mechanisms are used to generate jets with various ranges of jet diameters: ~150 micrometer inertial jets from liquid pressurized through a small orifice, ~50 micrometer flow focused jets, and ~20 micrometer electrified Taylor-cone jets. The transverse perturbations enable systematic triggering of varicose and whipping instabilities, and consequently a wide range of remarkable phenomena emerge. For inertial jets with zero or low charge levels, only varicose instability is observable due to suppressed whipping instability. At modest charge levels, inertia jets can respond to the fundamental perturbation frequency as well as the second harmonic of the perturbation frequency. Highly charged jets such as fine jets generated from Taylor cones exhibit distinct behavior for different perturbation wavenumber x. Typical behavior include: whipping jets with superimposed varicose instability at small x, jet bifurcation from crossover of whipping and varicose instabilities at x~0.5, Coulombic fission owing to the surge of surface charge density as the slender liquid segments recover spherical shapes at x~0.7, and simple varicose mode near wave numbers of unity. The phenomena observed in this work may be explained by a linear model and rationalized by the phase diagram in the space of wave number and dimensionless charge levels. The experimental apparatus used in this dissertation is simple, non-intrusive, and scalable to a linear array of jets. The rich phenomena combined with the versatile apparatus may spawn new research directions such as regulated electrospinning, generating strictly monodisperse micro/nano droplets, and manufacturing of non-spherical particles from drying droplets that undergo controlled Coulombic fissions.
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Date Issued
2014
Identifier
CFE0005744, ucf:50086
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005744
EFFECTS OF SIMULTANEOUS EXERCISE AND SPEECH TASKS ON THE PERCEPTION OF EFFORT AND VOCAL MEASURES IN AEROBIC INSTRUCTURS
Title
EFFECTS OF SIMULTANEOUS EXERCISE AND SPEECH TASKS ON THE PERCEPTION OF EFFORT AND VOCAL MEASURES IN AEROBIC INSTRUCTURS.
Creator
Koblick, Heather, Hoffman-Ruddy, Bari, University of Central Florida
Abstract / Description
The purpose of this study was to investigate the effects of voice production and perception of dyspnea in aerobic instructors during simultaneous tasks of exercise and speech production. The study aimed to document changes that occur during four conditions: 1) voice production without exercise and no use of amplification; 2) voice production without exercise and the use of amplification; 3) voice production during exercise without the use of amplification; 4) voice production during exercise...
Show moreThe purpose of this study was to investigate the effects of voice production and perception of dyspnea in aerobic instructors during simultaneous tasks of exercise and speech production. The study aimed to document changes that occur during four conditions: 1) voice production without exercise and no use of amplification; 2) voice production without exercise and the use of amplification; 3) voice production during exercise without the use of amplification; 4) voice production during exercise with the use of amplification. Participants included ten aerobic instructors (two male and eight female). The dependent variables included vocal intensity, average fundamental frequency (F0), noise-to-harmonic ratio (NHR), jitter percent (jitt %), shimmer percent (shim %), and participants' self-perception of dyspnea. The results indicated that speech alone, whether it was with or without amplification, had no effect on the sensation of dyspnea. However, when combining speech with exercise, the speech task became increasingly difficult, even more so without the use of amplification. Exercise was observed to inhibit vocal loudness levels as vocal intensity measures were lowest in the conditions with exercise with the use of amplification. Increases in F0 occurred in conditions involving exercise without the use of amplification. Moreover, four participants in various conditions exhibited frequencies that diverged from their gender's normal range. Participants' NHR increased during periods of exercise, however no participants were found to have NHR measures outside the normal range. Four participants were found to have moderate laryngeal pathology that was hemorrhagic in nature. Findings suggest that traditional treatment protocols may need to be modified beyond hygienic approaches in order to address both the respiratory and laryngeal work-loads that are encountered in this population and others involving similar occupational tasks.
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Date Issued
2004
Identifier
CFE0000274, ucf:46234
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000274
FPGA-BASED DESIGN OF A MAXIMUM-POWER-POINT TRACKING SYSTEM FOR SPACE APPLICATIONS
Title
FPGA-BASED DESIGN OF A MAXIMUM-POWER-POINT TRACKING SYSTEM FOR SPACE APPLICATIONS.
Creator
Persen, Todd, Ejnioui, Abdel, University of Central Florida
Abstract / Description
Satellites need a source of power throughout their missions to help them remain operational for several years. The power supplies of these satellites, provided primarily by solar arrays, must have high efficiencies and low weights in order to meet stringent design constraints. Power conversion from these arrays is required to provide robust and reliable conversion which performs optimally in varying conditions of peak power, solar flux, and occlusion conditions. Since the role of these arrays...
Show moreSatellites need a source of power throughout their missions to help them remain operational for several years. The power supplies of these satellites, provided primarily by solar arrays, must have high efficiencies and low weights in order to meet stringent design constraints. Power conversion from these arrays is required to provide robust and reliable conversion which performs optimally in varying conditions of peak power, solar flux, and occlusion conditions. Since the role of these arrays is to deliver power, one of the principle factors in achieving maximum power output from an array is tracking and holding its maximum-power point. This point, which varies with temperature, insolation, and loading conditions, must be continuously monitored in order to react to rapid changes. Until recently, the control of maximum power point tracking (MPPT) has been implemented in microcontrollers and digital signal processors (DSPs). While DSPs can provide a reasonable performance, they do not provide the advantages that field-programmable gate arrays (FPGA) chips can potentially offer to the implementation of MPPT control. In comparison to DSP implementations, FPGAs offer lower cost implementations since the functions of various components can be integrated onto the same FPGA chip as opposed to DSPs which can perform only DSP-related computations. In addition, FPGAs can provide equivalent or higher performance with the customization potential of an ASIC. Because FPGAs can be reprogrammed at any time, repairs can be performed in-situ while the system is running thus providing a high degree of robustness. Beside robustness, this reprogrammability can provide a high level of (i) flexibility that can make upgrading an MPPT control system easy by merely updating or modifying the MPPT algorithm running on the FPGA chip, and (ii) expandability that makes expanding an FPGA-based MPPT control system to handle multi-channel control. In addition, this reprogrammability provides a level of testability that DSPs cannot match by allowing the emulation of the entire MPPT control system onto the FPGA chip. This thesis proposes an FPGA-based implementation of an MPPT control system suitable for space applications. At the core of this system, the Perturb-and-observe algorithm is used to track the maximum power point. The algorithm runs on an Alera FLEX 10K FPGA chip. Additional functional blocks, such as the ADC interface, FIR filter, dither generator, and DAC interface, needed to support the MPPT control system are integrated within the same FPGA device thus streamlining the part composition of the physical prototype used to build this control system.
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Date Issued
2004
Identifier
CFE0000287, ucf:46232
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000287
The Power of Quantum Walk: Insights, Implementation, and Applications
Title
The Power of Quantum Walk: Insights, Implementation, and Applications.
Creator
Chiang, Chen-Fu, Wocjan, Pawel, Marinescu, Dan, Dechev, Damian, Mucciolo, Eduardo, University of Central Florida
Abstract / Description
In this thesis, I investigate quantum walks in quantum computing from threeaspects: the insights, the implementation, and the applications. Quantum walks are the quantum analogue of classical random walks. For the insights of quantum walks, I list and explain the required components for quantizing a classical random walk into a quantum walk. The components are, for instance, Markov chains, quantum phase estimation, and quantum spectrum theorem. I then demonstrate how the product of two...
Show moreIn this thesis, I investigate quantum walks in quantum computing from threeaspects: the insights, the implementation, and the applications. Quantum walks are the quantum analogue of classical random walks. For the insights of quantum walks, I list and explain the required components for quantizing a classical random walk into a quantum walk. The components are, for instance, Markov chains, quantum phase estimation, and quantum spectrum theorem. I then demonstrate how the product of two reflections in the walk operator provides a quadratic speed-up, in comparison to the classical counterpart. For the implementation of quantum walks, I show the construction of an efficient circuit for realizing one single step of the quantum walk operator. Furthermore, I devise a more succinct circuit to approximately implement quantum phase estimation with constant precision controlled phase shift operators. From an implementation perspective, efficient circuits are always desirable because the realization of a phase shift operator with high precision would be a costly task and a critical obstacle. For the applications of quantum walks, I apply the quantum walk technique along with other fundamental quantum techniques, such as phase estimation, to solve the partition function problem. However, there might be some scenario in which the speed-up of spectral gap is insignificant. In a situation like that that,I provide an amplitude amplification-based approach to prepare the thermal Gibbs state. Such an approach is useful when the spectral gap is extremely small. Finally, I further investigate and explore the effect of noise (perturbation)on the performance of quantum walks.
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Date Issued
2011
Identifier
CFE0004094, ucf:49148
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004094
INITIAL-VALUE TECHNIQUE FOR SINGULARLY PERTURBED TWO POINT BOUNDARY VALUE PROBLEMS VIA CUBIC SPLINE
Title
INITIAL-VALUE TECHNIQUE FOR SINGULARLY PERTURBED TWO POINT BOUNDARY VALUE PROBLEMS VIA CUBIC SPLINE.
Creator
Negron, Luis, Mohapatra, Ram, University of Central Florida
Abstract / Description
A recent method for solving singular perturbation problems is examined. It is designed for the applied mathematician or engineer who needs a convenient, useful tool that requires little preparation and can be readily implemented using little more than an industry-standard software package for spreadsheets. In this paper, we shall examine singularly perturbed two point boundary value problems with the boundary layer at one end point. An initial-value technique is used for its solution by...
Show moreA recent method for solving singular perturbation problems is examined. It is designed for the applied mathematician or engineer who needs a convenient, useful tool that requires little preparation and can be readily implemented using little more than an industry-standard software package for spreadsheets. In this paper, we shall examine singularly perturbed two point boundary value problems with the boundary layer at one end point. An initial-value technique is used for its solution by replacing the problem with an asymptotically equivalent first order problem, which is, in turn, solved as an initial value problem by using cubic splines. Numerical examples are provided to show that the method presented provides a fine approximation of the exact solution. The first chapter provides some background material to the cubic spline and boundary value problems. The works of several authors and a comparison of different solution methods are also discussed. Finally, some background into the specific singularly perturbed boundary value problems is introduced. The second chapter contains calculations and derivations necessary for the cubic spline and the initial value technique which are used in the solutions to the boundary value problems. The third chapter contains some worked numerical examples and the numerical data obtained along with most of the tables and figures that describe the solutions. The thesis concludes with some reflections on the results obtained and some discussion of the error bounds on the calculated approximations to the exact solutions for the numeric examples discussed.
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Date Issued
2010
Identifier
CFE0003460, ucf:48398
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003460
Image degradation due to surface scattering in the presence of aberrations
Title
Image degradation due to surface scattering in the presence of aberrations.
Creator
Choi, Narak, Harvey, James, Zeldovich, Boris, Moharam, M., Eastes, Richard, University of Central Florida
Abstract / Description
This dissertation focuses on the scattering phenomena by well-polished optical mirror surfaces. Specifically, predicting image degradation by surface scatter from rough mirror surfaces for a two-mirror telescope operating at extremely short wavelengths (9nm~30nm) is performed. To evaluate image quality, surface scatter is predicted from the surface metrology data and the point spread function in the presence of both surface scatter and aberrations is calculated.For predicting the scattering...
Show moreThis dissertation focuses on the scattering phenomena by well-polished optical mirror surfaces. Specifically, predicting image degradation by surface scatter from rough mirror surfaces for a two-mirror telescope operating at extremely short wavelengths (9nm~30nm) is performed. To evaluate image quality, surface scatter is predicted from the surface metrology data and the point spread function in the presence of both surface scatter and aberrations is calculated.For predicting the scattering intensity distribution, both numerical and analytic methods are considered. Among the numerous analytic methods, the small perturbation method (classical Rayleigh-Rice surface scatter theory), the Kirchhoff approximation method (classical Beckman-Kirchhoff surface scatter theory), and the generalized Harvey-Shack surface scatter theory are adopted. As a numerical method, the integral equation method (method of moments) known as a rigorous solution is discussed. Since the numerical method is computationally too intensive to obtain the scattering prediction directly for the two mirror telescope, it is used for validating the three analytic approximate methods in special cases. In our numerical comparison work, among the three approximate methods, the generalized Harvey-Shack model shows excellent agreement to the rigorous solution and it is used to predict surface scattering from the mirror surfaces.Regarding image degradation due to surface scatter in the presence of aberrations, it is shown that the composite point spread function is obtained in explicit form in terms of convolutions of the geometrical point spread function and scaled bidirectional scattering distribution functions of the individual surfaces of the imaging system. The approximations and assumptions in this formulation are discussed. The result is compared to the irradiance distribution obtained using commercial non-sequential ray tracing software for the case of a two-mirror telescope operating at the extreme ultra-violet wavelengths and the two results are virtually identical. Finally, the image degradation due to the surface scatter from the mirror surfaces and the aberration of the telescope is evaluated in terms of the fractional ensquared energy (for different wavelengths and field angles) which is commonly used as an image quality requirement on many NASA astronomy programs.
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Date Issued
2012
Identifier
CFE0004289, ucf:49492
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004289
Transient and Distributed Algorithms to Improve Islanding Detection Capability of Inverter Based Distributed Generation
Title
Transient and Distributed Algorithms to Improve Islanding Detection Capability of Inverter Based Distributed Generation.
Creator
Alhosani, Mohamed, Qu, Zhihua, Mikhael, Wasfy, Haralambous, Michael, Behal, Aman, Xu, Chengying, University of Central Florida
Abstract / Description
Recently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten...
Show moreRecently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten years in anticipation of the tremendous increase in the penetration of Distributed Generation (DG) in distribution system. This work proposes new IDMs that rely on transient and distributed behaviors to improve integrity and performance of DGs while maintaining multi-DG islanding detection capability.In this thesis, the following questions have been addressed: How to utilize the transient behavior arising from an islanding condition to improve detectability and robust performance of IDMs in a distributive manner? How to reduce the negative stability impact of the well-known Sandia Frequency Shift (SFS) IDM while maintaining its islanding detection capability? How to incorporate the perturbations provided by each of DGs in such a way that the negative interference of different IDMs is minimized without the need of any type of communication among the different DGs?It is shown that the proposed techniques are local, scalable and robust against different loading conditions and topology changes. Also, the proposed techniques can successfully distinguish an islanding condition from other disturbances that may occur in power system networks. This work improves the efficiency, reliability and safety of integrated DGs, which presents a necessary advance toward making electric power grids a smart grid.
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Date Issued
2013
Identifier
CFE0005295, ucf:50567
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005295