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(21 - 40 of 48)
Pages
- Title
- LEARNING GEOMETRY-FREE FACE RE-LIGHTING.
- Creator
-
Moore, Thomas, Foroosh, Hassan, University of Central Florida
- Abstract / Description
-
The accurate modeling of the variability of illumination in a class of images is a fundamental problem that occurs in many areas of computer vision and graphics. For instance, in computer vision there is the problem of facial recognition. Simply, one would hope to be able to identify a known face under any illumination. On the other hand, in graphics one could imagine a system that, given an image, the illumination model could be identified and then used to create new images. In this thesis...
Show moreThe accurate modeling of the variability of illumination in a class of images is a fundamental problem that occurs in many areas of computer vision and graphics. For instance, in computer vision there is the problem of facial recognition. Simply, one would hope to be able to identify a known face under any illumination. On the other hand, in graphics one could imagine a system that, given an image, the illumination model could be identified and then used to create new images. In this thesis we describe a method for learning the illumination model for a class of images. Once the model is learnt it is then used to render new images of the same class under the new illumination. Results are shown for both synthetic and real images. The key contribution of this work is that images of known objects can be re-illuminated using small patches of image data and relatively simple kernel regression models. Additionally, our approach does not require any knowledge of the geometry of the class of objects under consideration making it relatively straightforward to implement. As part of this work we will examine existing geometric and image-based re-lighting techniques; give a detailed description of our geometry-free face re-lighting process; present non-linear regression and basis selection with respect to image synthesis; discuss system limitations; and look at possible extensions and future work.
Show less - Date Issued
- 2007
- Identifier
- CFE0001893, ucf:47394
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001893
- Title
- Cavity-Coupled Plasmonic Systems for Enhanced Light-Matter Interactions.
- Creator
-
Vazquez-Guardado, Abraham, Chanda, Debashis, Christodoulides, Demetrios, Abouraddy, Ayman, Moharam, Jim, Leuenberger, Michael, University of Central Florida
- Abstract / Description
-
Light-matter interaction is a pivotal effect that involves the synergetic interplay of electromag- netic fields with fundamental particles. In this regard localized surface plasmons (LSP) arise from coherent interaction of the electromagnetic field with the collective oscillation of free electrons in confined sub-wavelength environments. Their most attractive properties are strong field en- hancements at the near field, highly inhomogeneous, peculiar temporal and spatial distributions and...
Show moreLight-matter interaction is a pivotal effect that involves the synergetic interplay of electromag- netic fields with fundamental particles. In this regard localized surface plasmons (LSP) arise from coherent interaction of the electromagnetic field with the collective oscillation of free electrons in confined sub-wavelength environments. Their most attractive properties are strong field en- hancements at the near field, highly inhomogeneous, peculiar temporal and spatial distributions and unique polarization properties. LSP systems also offer a unique playground for fundamental electromagnetic physics where micro-scale systemic properties can be studied in the macro-scale. These important properties and opportunities are brought up in this work where I study hybrid cavity-coupled plasmonic systems in which the weak plasmonic element is far-field coupled with the photonic cavity by properly tuning its phase. In this work I preset the fundamental understand- ing of such a complex systems from the multi-resonance interaction picture along experimental demonstration. Using this platform and its intricate near fields I further demonstrate a novel mech- anism to generate superchiral light: a field polarization property that adds a degree of freedom to light-matter interactions at the nanoscale exploited in advanced sensing applications and surface effect processes. Finally, the detection of non-chiral analytes, such as proteins, neurotransmit- ters or nanoparticles, and more complex chiral analytes, such as proteins and its conformation states, amino acids or chiral molecules at low concentrations is demonstrated in several biosensing applications. The accompanied experiential demonstrations were accomplished using the nanoim- printing technique, which places the cavity-coupled hybrid plasmonic system as a unique platform towards realistic applications not limited by expensive lithographic techniques.
Show less - Date Issued
- 2018
- Identifier
- CFE0007418, ucf:52708
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007418
- Title
- Harnessing Spatial Intensity Fluctuations for Optical Imaging and Sensing.
- Creator
-
Akhlaghi Bouzan, Milad, Dogariu, Aristide, Saleh, Bahaa, Pang, Sean, Atia, George, University of Central Florida
- Abstract / Description
-
Properties of light such as amplitude and phase, temporal and spatial coherence, polarization, etc. are abundantly used for sensing and imaging. Regardless of the passive or active nature of the sensing method, optical intensity fluctuations are always present! While these fluctuations are usually regarded as noise, there are situations where one can harness the intensity fluctuations to enhance certain attributes of the sensing procedure. In this thesis, we developed different sensing...
Show moreProperties of light such as amplitude and phase, temporal and spatial coherence, polarization, etc. are abundantly used for sensing and imaging. Regardless of the passive or active nature of the sensing method, optical intensity fluctuations are always present! While these fluctuations are usually regarded as noise, there are situations where one can harness the intensity fluctuations to enhance certain attributes of the sensing procedure. In this thesis, we developed different sensing methodologies that use statistical properties of optical fluctuations for gauging specific information. We examine this concept in the context of three different aspects of computational optical imaging and sensing. First, we study imposing specific statistical properties to the probing field to image or characterize certain properties of an object through a statistical analysis of the spatially integrated scattered intensity. This offers unique capabilities for imaging and sensing techniques operating in highly perturbed environments and low-light conditions. Next, we examine optical sensing in the presence of strong perturbations that preclude any controllable field modification. We demonstrate that inherent properties of diffused coherent fields and fluctuations of integrated intensity can be used to track objects hidden behind obscurants. Finally, we address situations where, due to coherent noise, image accuracy is severely degraded by intensity fluctuations. By taking advantage of the spatial coherence properties of optical fields, we show that this limitation can be effectively mitigated and that a significant improvement in the signal-to-noise ratio can be achieved even in one single-shot measurement. The findings included in this dissertation illustrate different circumstances where optical fluctuations can affect the efficacy of computational optical imaging and sensing. A broad range of applications, including biomedical imaging and remote sensing, could benefit from the new approaches to suppress, enhance, and exploit optical fluctuations, which are described in this dissertation.
Show less - Date Issued
- 2017
- Identifier
- CFE0007274, ucf:52200
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007274
- Title
- COMPUTER TECHNOLOGYIN THE DESIGN PROCESS.
- Creator
-
Montague, Gregory, Scott, Bert, University of Central Florida
- Abstract / Description
-
This is a study of computer technologyÂÂ's impact on the theatrical design process. The tools of communication provided by technology were studied, and an analysis was conducted in the classroom of Digital Rendering, Digital Rendering Videos, and 3d CADD. After-wards, these tools were applied to an actual production of West Side Story where, with the addition of 3d light simulation software, the tools were used to communicate the design ideas from the lighting designer...
Show moreThis is a study of computer technologyÂÂ's impact on the theatrical design process. The tools of communication provided by technology were studied, and an analysis was conducted in the classroom of Digital Rendering, Digital Rendering Videos, and 3d CADD. After-wards, these tools were applied to an actual production of West Side Story where, with the addition of 3d light simulation software, the tools were used to communicate the design ideas from the lighting designer to the director. The goal of this process was to provide a ÂÂ"real to lifeÂÂ" virtual representation of the show to the director with the least amount of confusion. An additional goal was to test the limits and functions of the software; trying to learn all the benefits that could be provided to the process of mounting a theatrical production.
Show less - Date Issued
- 2010
- Identifier
- CFE0003032, ucf:48365
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003032
- Title
- The Effect of Morphology on Reflectance in Silicon Nanowires Grown by Electroless Etching.
- Creator
-
Velez, Victor, Sundaram, Kalpathy, Kapoor, Vikram, Yuan, Jiann-Shiun, Abdolvand, Reza, Kar, Aravinda, University of Central Florida
- Abstract / Description
-
The strong light trapping properties of Silicon Nanowires have attracted much interest in the past few years for the conversion of sun energy into conventional electricity. Studies have been completed for many researchers to reduce the cost of fabrication and reflectance of solar light in these nanostructures to make a cheaper and more efficient solar cell technology by using less equipment for fabrication and employing different materials and solution concentrations. Silver, a conducting and...
Show moreThe strong light trapping properties of Silicon Nanowires have attracted much interest in the past few years for the conversion of sun energy into conventional electricity. Studies have been completed for many researchers to reduce the cost of fabrication and reflectance of solar light in these nanostructures to make a cheaper and more efficient solar cell technology by using less equipment for fabrication and employing different materials and solution concentrations. Silver, a conducting and stable metal is used these days as a precursor to react with silicon and then form the nanowires. Its adequate selection of solution concentration for a size of silicon substrate and the treatment for post-cleaning of silver dendrites make it a viable method among the others. It is an aim of this research to obtain significant low reflectance across the visible solar light range. Detailed concentration, fabrication and reflectance studies is carried out on silicon wafer in order to expand knowledge and understanding.In this study, electroless etching technique has been used as the growth mechanism of SiNWs at room temperature. Optimum ratios of solution concentration and duration for different sizes of exposed area to grow tall silicon nanowires derived from experimentation are presented. Surface imaging of the structures and dimension of length and diameter have been determined by Scanner Electron Microscopy (SEM) and the reflectance in the optical range in silicon nanowires has been make using UV-Visible Spectrophotometer.
Show less - Date Issued
- 2017
- Identifier
- CFE0006815, ucf:51807
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006815
- Title
- SAFETY ISSUES OF RED-LIGHT RUNNING AND UNPROTECTED LEFT-TURN AT SIGNALIZED INTERSECTIONS.
- Creator
-
Yan, Xuedong, Radwan, Essam, University of Central Florida
- Abstract / Description
-
Crashes categorized as running red light or left turning are most likely to occur at signalized intersections and resulted in substantial severe injuries and property damages. This dissertation mainly focused on these two types of vehicle crashes and the research methodology involved several perspectives. To examine the overall characteristics of red-light running and left-turning crashes, firstly, this study applied 1999-2001 Florida traffic crash data to investigate the accident propensity...
Show moreCrashes categorized as running red light or left turning are most likely to occur at signalized intersections and resulted in substantial severe injuries and property damages. This dissertation mainly focused on these two types of vehicle crashes and the research methodology involved several perspectives. To examine the overall characteristics of red-light running and left-turning crashes, firstly, this study applied 1999-2001 Florida traffic crash data to investigate the accident propensity of three aspects of risk factors related to traffic environments, driver characteristics, and vehicle types. A quasi-induced exposure concept and statistical techniques including classification tree model and multiple logistic regression were used to perform this analysis. Secondly, the UCF driving simulator was applied to test the effect of a proposed new pavement marking countermeasure which purpose is to reduce the red-light running rate at signalized intersections. The simulation experiment results showed that the total red-light running rate with marking is significantly lower than that without marking. Moreover, deceleration rate of stopping drivers with marking for the higher speed limit are significantly less than those without marking. These findings are encouraging and suggesting that the pavement marking may result in safety enhancement as far as right-angle and rear-end traffic crashes at signalized intersections. Thirdly, geometric models to compute sight distances of unprotected left-turns were developed for different signalized intersection configurations including a straight approach leading to a straight one, a straight approach leading to a curved one, and a curved approach leading to a curved one. The models and related analyses can be used to layout intersection design or evaluate the sight distance problem of an existing intersection configuration to ensure safe left-turn maneuvers by drivers.
Show less - Date Issued
- 2005
- Identifier
- CFE0000451, ucf:46389
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000451
- Title
- SAFETY ISSUES OF RED-LIGHT RUNNING AND UNPROTECTED LEFT-TURN AT SIGNALIZED INTERSECTIONS.
- Creator
-
Yan, Xuedong, Radwan, Essam, University of Central Florida
- Abstract / Description
-
Crashes categorized as running red light or left turning are most likely to occur at signalized intersections and resulted in substantial severe injuries and property damages. This dissertation mainly focused on these two types of vehicle crashes and the research methodology involved several perspectives. To examine the overall characteristics of red-light running and left-turning crashes, firstly, this study applied 1999-2001 Florida traffic crash data to investigate the accident propensity...
Show moreCrashes categorized as running red light or left turning are most likely to occur at signalized intersections and resulted in substantial severe injuries and property damages. This dissertation mainly focused on these two types of vehicle crashes and the research methodology involved several perspectives. To examine the overall characteristics of red-light running and left-turning crashes, firstly, this study applied 1999-2001 Florida traffic crash data to investigate the accident propensity of three aspects of risk factors related to traffic environments, driver characteristics, and vehicle types. A quasi-induced exposure concept and statistical techniques including classification tree model and multiple logistic regression were used to perform this analysis. Secondly, the UCF driving simulator was applied to test the effect of a proposed new pavement marking countermeasure which purpose is to reduce the red-light running rate at signalized intersections. The simulation experiment results showed that the total red-light running rate with marking is significantly lower than that without marking. Moreover, deceleration rate of stopping drivers with marking for the higher speed limit are significantly less than those without marking. These findings are encouraging and suggesting that the pavement marking may result in safety enhancement as far as right-angle and rear-end traffic crashes at signalized intersections. Thirdly, geometric models to compute sight distances of unprotected left-turns were developed for different signalized intersection configurations including a straight approach leading to a straight one, a straight approach leading to a curved one, and a curved approach leading to a curved one. The models and related analyses can be used to layout intersection design or evaluate the sight distance problem of an existing intersection configuration to ensure safe left-turn maneuvers by drivers.
Show less - Date Issued
- 2005
- Identifier
- CFE0000401, ucf:46347
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000401
- Title
- LASER ENHANCED DOPING FOR SILICON CARBIDE WHITE LIGHTEMITTING DIODES.
- Creator
-
Bet, Sachin, Kar, Aravinda, University of Central Florida
- Abstract / Description
-
This work establishes a solid foundation for the use of indirect band gap semiconductors for light emitting application and presents the work on development of white light emitting diodes (LEDs) in silicon carbide (SiC). Novel laser doping has been utilized to fabricate white light emitting diodes in 6H-SiC (n-type N) and 4H-SiC (p-type Al) wafers. The emission of different colors to ultimately generate white light is tailored on the basis of donor acceptor pair (DAP) recombination mechanism...
Show moreThis work establishes a solid foundation for the use of indirect band gap semiconductors for light emitting application and presents the work on development of white light emitting diodes (LEDs) in silicon carbide (SiC). Novel laser doping has been utilized to fabricate white light emitting diodes in 6H-SiC (n-type N) and 4H-SiC (p-type Al) wafers. The emission of different colors to ultimately generate white light is tailored on the basis of donor acceptor pair (DAP) recombination mechanism for luminescence. A Q-switched Nd:YAG pulse laser (1064 nm wavelength) was used to carry out the doping experiments. The p and n regions of the white SiC LED were fabricated by laser doping an n-type 6H-SiC and p-type 4H-SiC wafer substrates with respective dopants. Cr, B and Al were used as p-type dopants (acceptors) while N and Se were used as n-type dopants (donors). Deep and shallow donor and acceptor impurity level states formed by these dopants tailor the color properties for pure white light emission. The electromagnetic field of lasers and non-equilibrium doping conditions enable laser doping of SiC with increased dopant diffusivity and enhanced solid solubility. A thermal model is utilized to determine the laser doping parameters for temperature distribution at various depths of the wafer and a diffusion model is presented including the effects of Fick's diffusion, laser electromagnetic field and thermal stresses due to localized laser heating on the mass flux of dopant atoms. The dopant diffusivity is calculated as a function of temperature at different depths of the wafer based on measured dopant concentration profile. The maximum diffusivities achieved in this study are 4.6110-10 cm2/s at 2898 K and 6.9210-12 cm2/s at 3046 K for Cr in 6H-SiC and 4H-SiC respectively. Secondary ion mass spectrometric (SIMS) analysis showed the concentration profile of Cr in SiC having a penetration depth ranging from 80 nm in p-type 4H-SiC to 1.5 m in n-type 6H-SiC substrates respectively. The SIMS data revealed enhanced solid solubility (2.291019 cm-3 in 6H-SiC and 1.421919 cm-3 in 4H-SiC) beyond the equilibrium limit (31017 cm-3 in 6H-SiC above 2500 C) for Cr in SiC. It also revealed similar effects for Al and N. The roughness, surface chemistry and crystalline integrity of the doped sample were examined by optical interferometer, energy dispersive X-ray spectrometry (EDS) and transmission electron microscopy (TEM) respectively. Inspite of the larger atomic size of Cr compared to Si and C, the non-equilibrium conditions during laser doping allow effective incorporation of dopant atoms into the SiC lattice without causing any damage to the surface or crystal lattice. Deep Level Transient Spectroscopy (DLTS) confirmed the deep level acceptor state of Cr with activation energies of Ev+0.80 eV in 4H-SiC and Ev+0.45 eV in 6H-SiC. The Hall Effect measurements showed the hole concentration to be 1.981019 cm-3 which is almost twice the average Cr concentration (11019 cm-3) obtained from the SIMS data. These data confirmed that almost all of the Cr atoms were completely activated to the double acceptor state by the laser doping process without requiring any subsequent annealing step. Electroluminescence studies showed blue (460-498 nm), blue-green (500-520 nm) green (521-575 nm), and orange (650-690 nm) wavelengths due to radiative recombination transitions between donor-acceptors pairs of N-Al, N-B, N-Cr and Cr-Al respectively, while a prominent violet (408 nm) wavelength was observed due to transitions from the nitrogen level to the valence band level. The red (698-738 nm) luminescence was mainly due to metastable mid-bandgap states, however under high injection current it was due to the quantum mechanical phenomenon pertaining to band broadening and overlapping. This RGB combination produced a broadband white light spectrum extending from 380 to 900 nm. The color space tri-stimulus values for 4H-SiC doped with Cr and N were X = 0.3322, Y = 0.3320 and Z = 0.3358 as per 1931 CIE (International Commission on Illumination) corresponding to a color rendering index of 96.56 and the color temperature of 5510 K. And for 6H-SiC n-type doped with Cr and Al, the color space tri-stimulus values are X = 0.3322, Y = 0.3320 and Z = 0.3358. The CCT was 5338 K, which is very close to the incandescent lamp (or black body) and lies between bright midday sun (5200 K) and average daylight (5500 K) while CRI was 98.32. Similar white LED's were also fabricated using Cr, Al, Se as one set of dopants and B, Al, N as another.
Show less - Date Issued
- 2008
- Identifier
- CFE0002362, ucf:47808
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002362
- Title
- PROVIDING A BETTER UNDERSTANDING FOR THE MOTORIST BEHAVIOR TOWARDS SIGNAL CHANGE.
- Creator
-
Elmitiny, Noor, Radwan, Essam, University of Central Florida
- Abstract / Description
-
This research explores the red light running phenomena and offer a better understanding of the factors associated with it. The red light running is a type of traffic violation that can lead to angle crash and the most common counter measure is installing a red light running cameras. Red light running cameras some time can reduce the rates of red light running but because of the increased worry of the public towards crossing the intersection it can cause an increase in rear end crashes. Also...
Show moreThis research explores the red light running phenomena and offer a better understanding of the factors associated with it. The red light running is a type of traffic violation that can lead to angle crash and the most common counter measure is installing a red light running cameras. Red light running cameras some time can reduce the rates of red light running but because of the increased worry of the public towards crossing the intersection it can cause an increase in rear end crashes. Also the public opinion of the red light running cameras is that they are a revenue generator for the local counties and not a concern of public safety. Further more, they consider this type of enforcement as violation of privacy. There was two ways to collect the data needed for the research. One way is through a tripod cameras setup temporarily placed at the intersection. This setup can collect individual vehicles caught in the change phase with specific information about their reactions and conditions. This required extensive manual analysis for the recorded videos plus data could not be collected during adverse weather conditions. The second way was using traffic monitoring cameras permanently located at the site to collect red light running information and the simultaneous traffic conditions. This system offered more extensive information since the cameras monitor the traffic 24/7 collecting data directly. On the other hand this system lacked the ability to identify the circumstances associated with individual red light running incidents. The research team finally decided to use the two methods to study the red light running phenomena aiming to combine the benefits of the two systems. During the research the team conducted an experiment to test a red light running countermeasure in the field and evaluate the public reaction and usage of this countermeasure. The marking was previously tested in a driving simulator and proved to be successful in helping the drivers make better stop/go decisions thus reducing red light running rates without increasing the rear-end crashes. The experiment was divided into three phases; before marking installation called "before", after marking installation called "after', and following a media campaign designed to inform the public about the use of the marking the third phase called "after media" The behavior study that aimed at analyzing the motorist reactions toward the signal change interval identified factors which contributed to red light running. There important factors were: distance from the stop bar, speed of traffic, leading or following in the traffic, vehicle type. It was found that a driver is more likely to run red light following another vehicle in the intersection. Also the speeding vehicles can clear the intersection faster thus got less involved in red light running violations. The proposed "Signal Ahead" marking was found to have a very good potential as a red light running counter measure. The red light running rates in the test intersection dropped from 53 RLR/hr/1000veh for the "before" phase, to 24 RLR/hr/1000veh for the "after media" phase. The marking after media analysis period found that the marking can help the driver make stop/go decision as the dilemma zone decreased by 50 ft between the "before" and the "after media" periods. Analysis of the traffic condition associated with the red light running it revealed that relation between the traffic conditions and the red light running is non-linear, with some interactions between factors. The most important factors included in the model were: traffic volume, average speed of traffic, the percentage of green time, the percentage of heavy vehicles, the interaction between traffic volume and percentage of heavy vehicles. The most interesting finding was the interaction between the volume and the percent of heavy vehicles. As the volume increased the effect of the heavy vehicles reversed from reducing the red light running to increasing the red light. This finding may be attributed to the sight blocking that happens when a driver of a passenger car follows a larger heavy vehicle, and can be also explained by the potential frustration experienced by the motorist resulting from driving behind a bigger vehicle.
Show less - Date Issued
- 2009
- Identifier
- CFE0002757, ucf:48118
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002757
- Title
- ANALYSIS AND DESIGN OF WIDE-ANGLE FOVEATED OPTICAL SYSTEMS.
- Creator
-
Curatu, George, Harvey, James, University of Central Florida
- Abstract / Description
-
The development of compact imaging systems capable of transmitting high-resolution images in real-time while covering a wide field-of-view (FOV) is critical in a variety of military and civilian applications: surveillance, threat detection, target acquisition, tracking, remote operation of unmanned vehicles, etc. Recently, optical foveated imaging using liquid crystal (LC) spatial light modulators (SLM) has received considerable attention as a potential approach to reducing size and...
Show moreThe development of compact imaging systems capable of transmitting high-resolution images in real-time while covering a wide field-of-view (FOV) is critical in a variety of military and civilian applications: surveillance, threat detection, target acquisition, tracking, remote operation of unmanned vehicles, etc. Recently, optical foveated imaging using liquid crystal (LC) spatial light modulators (SLM) has received considerable attention as a potential approach to reducing size and complexity in fast wide-angle lenses. The fundamental concept behind optical foveated imaging is reducing the number of elements in a fast wide-angle lens by placing a phase SLM at the pupil stop to dynamically compensate aberrations left uncorrected by the optical design. In the recent years, considerable research and development has been conducted in the field of optical foveated imaging based on the LC SLM technology, and several foveated optical systems (FOS) prototypes have been built. However, most research has been focused so far on the experimental demonstration of the basic concept using off the shelf components, without much concern for the practicality or the optical performance of the systems. Published results quantify only the aberration correction capabilities of the FOS, often claiming diffraction limited performance at the region of interest (ROI). However, these results have continually overlooked diffraction effects on the zero-order efficiency and the image quality. The research work presented in this dissertation covers the methods and results of a detailed theoretical research study on the diffraction analysis, image quality, design, and optimization of fast wide-angle FOSs based on the current transmissive LC SLM technology. The amplitude and phase diffraction effects caused by the pixelated aperture of the SLM are explained and quantified, revealing fundamental limitations imposed by the current transmissive LC SLM technology. As a part of this study, five different fast wide-angle lens designs that can be used to build practical FOSs were developed, revealing additional challenges specific to the optical design of fast wide-angle systems, such as controlling the relative illumination, distortion, and distribution of aberrations across a wide FOV. One of the lens design examples was chosen as a study case to demonstrate the design, analysis, and optimization of a practical wide-angle FOS based on the current state-of-the-art transmissive LC SLM technology. The effects of fabrication and assembly tolerances on the image quality of fast wide-angle FOSs were also investigated, revealing the sensitivity of these fast well-corrected optical systems to manufacturing errors. The theoretical study presented in this dissertation sets fundamental analysis, design, and optimization guidelines for future developments in fast wide-angle FOSs based on transmissive SLM devices.
Show less - Date Issued
- 2009
- Identifier
- CFE0002584, ucf:48254
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002584
- Title
- FREEFORM REFLECTOR DESIGN WITH EXTENDED SOURCES.
- Creator
-
Fournier, Florian, Rolland, Jannick, University of Central Florida
- Abstract / Description
-
Reflector design stemmed from the need to shape the light emitted by candles or lamps. Over 2,000 years ago people realized that a mirror shaped as a parabola can concentrate light, and thus significantly boosts its intensity, to the point where objects can be set afire. Nowadays many applications require an accurate control of light, such as automotive headlights, streetlights, projection displays, and medical illuminators. In all cases light emitted from a light source can be shaped into a...
Show moreReflector design stemmed from the need to shape the light emitted by candles or lamps. Over 2,000 years ago people realized that a mirror shaped as a parabola can concentrate light, and thus significantly boosts its intensity, to the point where objects can be set afire. Nowadays many applications require an accurate control of light, such as automotive headlights, streetlights, projection displays, and medical illuminators. In all cases light emitted from a light source can be shaped into a desired target distribution with a reflective surface. Design methods for systems with rotational and translational symmetry were devised in the 1930s. However, the freeform reflector shapes required to illuminate targets with no such symmetries proved to be much more challenging to design. Even when the source is assumed to be a point, the reflector shape is governed by a set of second-order partial non-linear differential equations that cannot be solved with standard numerical integration techniques. An iterative approach to solve the problem for a discrete target, known as the method of supporting ellipsoids, was recently proposed by Oliker. In this research we report several efficient implementations of the method of supporting ellipsoids, based on the point source approximation, and we propose new reflector design techniques that take into account the extent of the source. More specifically, this work has led to three major achievements. First, a thorough analysis of the method of supporting ellipsoids was performed that resulted in two alternative implementations of the algorithm, which enable a fast generation of freeform reflector shapes within the point source approximation. We tailored the algorithm in order to provide control over the parameters of interest to the designers, such as the reflector scale and geometry. Second, the shape generation algorithm was used to analyze how source flux can be mapped onto the target. We derived the condition under which a given source-target mapping can be achieved with a smooth continuous surface, referred as the integrability condition. We proposed a method to derive mappings that satisfy the integrability condition. We then use these mappings to quickly generate reflector shapes that create continuous target distributions as opposed to reflectors generated with the method of supporting ellipsoids that create discrete sets of points on the target. We also show how mappings that do not satisfy the integrability condition can be achieved by introducing step discontinuities in the reflector surface. Third, we investigated two methods to design reflectors with extended sources. The first method uses a compensation approach where the prescribed target distribution is adjusted iteratively. This method is effective for compact sources and systems with rotational or translational symmetry. The second method tiles the source images created by a reflector designed with the method of supporting ellipsoids and then blends the source images together using scattering in order to obtain a continuous target distribution. This latter method is effective for freeform reflectors and target distributions with no sharp variations. Finally, several case studies illustrate how these methods can be successfully applied to design reflectors for general illumination applications such as street lighting or luminaires. We show that the proposed design methods can ease the design of freeform reflectors and provide efficient, cost-effective solutions that avoid unnecessary energy consumption and light pollution.
Show less - Date Issued
- 2010
- Identifier
- CFE0003311, ucf:48508
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003311
- Title
- The Suburban Nightmare: A Study of Atmosphere, Mood and Emotion.
- Creator
-
Sobrack, Ericka, Poindexter, Carla, Lotz, Theo, Kovach, Keith, University of Central Florida
- Abstract / Description
-
In this thesis body of work, I focus on the implied human presence through the lack of actual human figures. I believe there is more to say in a landscape with the absence of the figure, allowing the dialogue to be read and interpreted by a larger audience. I am particularly satisfied with White Knuckles, shown in figure 3, because I collide reason with imagination, thus contradicting the context and interpretation of the subject matter. In White Knuckles, I deal with formal elements such as...
Show moreIn this thesis body of work, I focus on the implied human presence through the lack of actual human figures. I believe there is more to say in a landscape with the absence of the figure, allowing the dialogue to be read and interpreted by a larger audience. I am particularly satisfied with White Knuckles, shown in figure 3, because I collide reason with imagination, thus contradicting the context and interpretation of the subject matter. In White Knuckles, I deal with formal elements such as composition, atmosphere, lightness and darkness as well as nuances of color. I have also considered the emotive impact the painting could reflect to the viewer, specifically feelings of tension and unease. The placement of the viewer outside the picture plane was carefully considered to suggest the audience is a participant in the suggested narrative. I often strive to create an ambiguous moment, reflecting feelings of uncertainty and apprehension. Like White Knuckles, my body of work employs unexpected narratives to reveal some of the uncomfortable truths of our human experience. I am interested in exploring the relationship between the mundane and the abnormal in the paintings, a feeling that could be described as a (")suburban nightmare.(")
Show less - Date Issued
- 2019
- Identifier
- CFE0007532, ucf:52587
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007532
- Title
- DESIGNING LIGHT FILTERS TO DETECT SKIN USING A LOW-POWERED SENSOR.
- Creator
-
Tariq, Muhammad, Wisniewski, Pamela, Gong, Boqing, Leavens, Gary, University of Central Florida
- Abstract / Description
-
Detection of nudity in photos and videos, especially prior to uploading to the internet, is vital to solving many problems related to adolescent sexting, the distribution of child pornography, and cyber-bullying. The problem with using nudity detection algorithms as a means to combat these problems is that: 1) it implies that a digitized nude photo of a minor already exists (i.e., child pornography), and 2) there are real ethical and legal concerns around the distribution and processing of...
Show moreDetection of nudity in photos and videos, especially prior to uploading to the internet, is vital to solving many problems related to adolescent sexting, the distribution of child pornography, and cyber-bullying. The problem with using nudity detection algorithms as a means to combat these problems is that: 1) it implies that a digitized nude photo of a minor already exists (i.e., child pornography), and 2) there are real ethical and legal concerns around the distribution and processing of child pornography. Once a camera captures an image, that image is no longer secure. Therefore, we need to develop new privacy-preserving solutions that prevent the digital capture of nude imagery of minors. My research takes a first step in trying to accomplish this long-term goal: In this thesis, I examine the feasibility of using a low-powered sensor to detect skin dominance (defined as an image comprised of 50% or more of human skin tone) in a visual scene. By designing four custom light filters to enhance the digital information extracted from 300 scenes captured with the sensor (without digitizing high-fidelity visual features), I was able to accurately detect a skin dominant scene with 83.7% accuracy, 83% precision, and 85% recall. The long-term goal to be achieved in the future is to design a low-powered vision sensor that can be mounted on a digital camera lens on a teen's mobile device to detect and/or prevent the capture of nude imagery. Thus, I discuss the limitations of this work toward this larger goal, as well as future research directions.
Show less - Date Issued
- 2017
- Identifier
- CFE0006806, ucf:51792
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006806
- Title
- Light Trapping in Thin Film Crystalline Silicon Solar Cells.
- Creator
-
Boroumand Azad, Javaneh, Chanda, Debashis, Peale, Robert, Del Barco, Enrique, Flitsiyan, Elena, Schoenfeld, Winston, University of Central Florida
- Abstract / Description
-
This dissertation presents numerical and experimental studies of a unified light trapping approach that is extremely important for all practical solar cells. A 2D hexagonal Bravais lattice diffractive pattern is studied in conjunction with the verification of the reflection mechanisms of single and double layer anti-reflective coatings in the broad range of wavelength 400 nm - 1100 nm. By varying thickness and conformity, we obtained the optimal parameters which minimize the broadband...
Show moreThis dissertation presents numerical and experimental studies of a unified light trapping approach that is extremely important for all practical solar cells. A 2D hexagonal Bravais lattice diffractive pattern is studied in conjunction with the verification of the reflection mechanisms of single and double layer anti-reflective coatings in the broad range of wavelength 400 nm - 1100 nm. By varying thickness and conformity, we obtained the optimal parameters which minimize the broadband reflection from the nanostructured crystalline silicon surface over a wide range of angle 0(&)deg;-65(&)deg;. While the analytical design of broadband, angle independent anti-reflection coatings on nanostructured surfaces remains a scientific challenge, numerical optimization proves a viable alternative, paving the path towards practical implementation of the light trapping solar cells. A 3 (&)#181;m thick light trapping solar cell is modeled in order to predict and maximize combined electron-photon harvesting in ultrathin crystalline silicon solar cells. It is shown that the higher charge carrier generation and collection in this design compensates the absorption and recombination losses and ultimately results in an increase in energy conversion efficiency. Further, 20 (&)#181;m and 100 (&)#181;m thick functional solar cells with the light trapping scheme are studied. The efficiency improvement is observed numerically and experimentally due to photon absorption enhancement in the light trapping cells with respect to a bare cell of same thickness.
Show less - Date Issued
- 2017
- Identifier
- CFE0006936, ucf:51654
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006936
- Title
- Transparent Oxide Semiconductor Gate based MOSFETs for Sensor Applications.
- Creator
-
Saikumar, Ashwin Kumar, Sundaram, Kalpathy, Wu, Thomas, Kapoor, Vikram, University of Central Florida
- Abstract / Description
-
Starting from small scale laboratories to the highly sophisticated industrial facilities, monitoring and control forms the most integral part. In order to perform this continuous monitoring we require an interface, that would operate between the system and its processing conditions and in turn which facilitates us to act accordingly. This interface is called as a sensor. There are various types of sensors available which have wide range of functionality in various different fields.The use of...
Show moreStarting from small scale laboratories to the highly sophisticated industrial facilities, monitoring and control forms the most integral part. In order to perform this continuous monitoring we require an interface, that would operate between the system and its processing conditions and in turn which facilitates us to act accordingly. This interface is called as a sensor. There are various types of sensors available which have wide range of functionality in various different fields.The use of transparent conducting oxide (TCO) in the field of sensor applications has increasedand has been the subject of extensive research. Good electrical properties, good optical properties, wide band gap, portability, easy processing, and low cost has led to the extensive research on TCO for sensor applications.For this research purpose two specific types of sensor applications namely, light sensing and humidity sensing were considered. For this purpose, two sets of metal-oxide-semiconductor field effect transistors (MOSFET) with one set having transparent aluminum doped zinc oxide and the other having indium tin oxide respectively as their gate metal was fabricated. The MOSFETs werefabricated using a four level mask and tested.
Show less - Date Issued
- 2014
- Identifier
- CFE0005547, ucf:50297
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005547
- Title
- A comparative analysis of different Dilemma Zone countermeasures at signalized intersections based on Cellular Automaton Model.
- Creator
-
Wu, Yina, Abdel-Aty, Mohamed, Lee, JaeYoung, Eluru, Naveen, University of Central Florida
- Abstract / Description
-
In the United States, intersections are among the most frequent locations for crashes. One of the major problems at signalized intersection is the dilemma zone, which is caused by false driver behavior during the yellow interval. This research evaluated driver behavior during the yellow interval at signalized intersections and compared different dilemma zone countermeasures. The study was conducted through four stages.First, the driver behavior during the yellow interval were collected and...
Show moreIn the United States, intersections are among the most frequent locations for crashes. One of the major problems at signalized intersection is the dilemma zone, which is caused by false driver behavior during the yellow interval. This research evaluated driver behavior during the yellow interval at signalized intersections and compared different dilemma zone countermeasures. The study was conducted through four stages.First, the driver behavior during the yellow interval were collected and analyzed. Eight variables, which are related to risky situations, are considered. The impact factors of drivers' stop/go decisions and the presence of the red-light running (RLR) violations were also analyzed. Second, based on the field data, a logistic model, which is a function of speed, distance to the stop line and the lead/follow position of the vehicle, was developed to predict drivers' stop/go decisions. Meanwhile, Cellular Automata (CA) models for the movement at the signalized intersection were developed. In this study, four different simulation scenarios were established, including the typical intersection signal, signal with flashing green phases, the intersection with pavement marking upstream of the approach, and the intersection with a new countermeasure: adding an auxiliary flashing indication next to the pavement marking. When vehicles are approaching the intersection with a speed lower than the speed limit of the intersection approach, the auxiliary flashing yellow indication will begin flashing before the yellow phase. If the vehicle that has not passed the pavement marking before the onset of the auxiliary flashing yellow indication and can see the flashing indication, the driver should choose to stop during the yellow interval. Otherwise, the driver should choose to go at the yellow duration. The CA model was employed to simulate the traffic flow, and the logistic model was applied as the stop/go decision rule. Dilemma situations that lead to rear-end crash risks and potential RLR risks were used to evaluate the different scenarios. According to the simulation results, the mean and standard deviation of the speed of the traffic flow play a significant role in rear-end crash risk situations, where a lower speed and standard deviation could lead to less rear-end risk situations at the same intersection. High difference in speed are more prone to cause rear-end crashes. With Respect to the RLR violations, the RLR risk analysis showed that the mean speed of the leading vehicle has important influence on the RLR risk in the typical intersection simulation scenarios as well as intersections with the flashing green phases' simulation scenario.Moreover, the findings indicated that the flashing green could not effectively reduce the risk probabilities. The pavement marking countermeasure had positive effects on reducing the risk probabilities if a platoon's mean speed was not under the speed used for designing the pavement marking. Otherwise, the risk probabilities for the intersection would not be reduced because of the increase in the RLR rate. The simulation results showed that the scenario with the pavement marking and an auxiliary indication countermeasure, which adds a flashing indication next to the pavement marking, had less risky situations than the other scenarios with the same speed distribution. These findings suggested the effectiveness of the pavement marking and an auxiliary indication countermeasure to reduce both rear-end collisions and RLR violations than other countermeasures.
Show less - Date Issued
- 2014
- Identifier
- CFE0005562, ucf:50291
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005562
- Title
- Metastable-State Photoacids: Synthesis, Properties, and Applications.
- Creator
-
Patel, Parth, Chumbimuni Torres, Karin, Hernandez, Florencio, Santra, Swadeshmukul, Beazley, Melanie, Lee, Woo Hyoung, University of Central Florida
- Abstract / Description
-
Reversible photochromic compounds have the ability to reversibly change its color when it absorbs photons of a particular wavelength. This process of color change is a consequence of structural changes within the compound, such as cis-trans photo-isomerization. Some examples of photochromic compounds are spiropyrans, spirooxazines, diarylethenes and azobenzenes. These compounds have been extensively studied for decades, and are used in various applications such as biomedicine, chemical...
Show moreReversible photochromic compounds have the ability to reversibly change its color when it absorbs photons of a particular wavelength. This process of color change is a consequence of structural changes within the compound, such as cis-trans photo-isomerization. Some examples of photochromic compounds are spiropyrans, spirooxazines, diarylethenes and azobenzenes. These compounds have been extensively studied for decades, and are used in various applications such as biomedicine, chemical sensors and harvesting solar energy. However, majority of photochromic compounds are initially activated by ultraviolet (UV) light. The use of UV light is harmful for biological applications and photo-degrade the compound over repeated use. To overcome these limitations, a new class of reversible photochromic compound was introduced, called metastable-state photoacid (mPAH). In brief, mPAH is a photochromic compound which can photo-dissociate its protons under visible light and can thermally re-capture the released protons efficiently in the dark. Based on this unique property, in this research, we (1) synthesized different mPAH, and (2) studied and characterized their physicochemical (acidity, kinetics, and optical) properties. Additionally, we (3) applied different visible light activated mPAHs towards light controllable polymeric-based ion-selective optodes for detection of calcium ions and sodium ions, and modulate fluorescence with pH. The research presented herein opens new avenues towards the synthesis of mPAH derivatives and could be applied to any proton-transfer process related applications which requires wireless controllability with high sensitivity.
Show less - Date Issued
- 2019
- Identifier
- CFE0007849, ucf:52769
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007849
- Title
- UNSUPERVISED BUILDING DETECTION FROM IRREGULARLY SPACED LIDAR AND AERIAL IMAGERY.
- Creator
-
Shorter, Nicholas, Kasparis, Takis, University of Central Florida
- Abstract / Description
-
As more data sources containing 3-D information are becoming available, an increased interest in 3-D imaging has emerged. Among these is the 3-D reconstruction of buildings and other man-made structures. A necessary preprocessing step is the detection and isolation of individual buildings that subsequently can be reconstructed in 3-D using various methodologies. Applications for both building detection and reconstruction have commercial use for urban planning, network planning for mobile...
Show moreAs more data sources containing 3-D information are becoming available, an increased interest in 3-D imaging has emerged. Among these is the 3-D reconstruction of buildings and other man-made structures. A necessary preprocessing step is the detection and isolation of individual buildings that subsequently can be reconstructed in 3-D using various methodologies. Applications for both building detection and reconstruction have commercial use for urban planning, network planning for mobile communication (cell phone tower placement), spatial analysis of air pollution and noise nuisances, microclimate investigations, geographical information systems, security services and change detection from areas affected by natural disasters. Building detection and reconstruction are also used in the military for automatic target recognition and in entertainment for virtual tourism. Previously proposed building detection and reconstruction algorithms solely utilized aerial imagery. With the advent of Light Detection and Ranging (LiDAR) systems providing elevation data, current algorithms explore using captured LiDAR data as an additional feasible source of information. Additional sources of information can lead to automating techniques (alleviating their need for manual user intervention) as well as increasing their capabilities and accuracy. Several building detection approaches surveyed in the open literature have fundamental weaknesses that hinder their use; such as requiring multiple data sets from different sensors, mandating certain operations to be carried out manually, and limited functionality to only being able to detect certain types of buildings. In this work, a building detection system is proposed and implemented which strives to overcome the limitations seen in existing techniques. The developed framework is flexible in that it can perform building detection from just LiDAR data (first or last return), or just nadir, color aerial imagery. If data from both LiDAR and aerial imagery are available, then the algorithm will use them both for improved accuracy. Additionally, the proposed approach does not employ severely limiting assumptions thus enabling the end user to apply the approach to a wider variety of different building types. The proposed approach is extensively tested using real data sets and it is also compared with other existing techniques. Experimental results are presented.
Show less - Date Issued
- 2009
- Identifier
- CFE0002783, ucf:48125
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002783
- Title
- White Light Continuum for Broadband Nonlinear Spectroscopy.
- Creator
-
Ensley, Trenton, Hagan, David, Vanstryland, Eric, Zeldovich, Boris, Christodoulides, Demetrios, Schulte, Alfons, University of Central Florida
- Abstract / Description
-
Supercontinuum (SC) generation, oftentimes referred to as white-light continuum (WLC), has been a subject of interest for more than 40 years. From the first observation of WLC in condensed media in the early 1970s to the first observation of WLC in gases in the mid-1980s, much work has been devoted to developing a framework for understanding the complex nature of this phenomenon as well as discovering its utility in various applications. The main effort of this dissertation is to develop a...
Show moreSupercontinuum (SC) generation, oftentimes referred to as white-light continuum (WLC), has been a subject of interest for more than 40 years. From the first observation of WLC in condensed media in the early 1970s to the first observation of WLC in gases in the mid-1980s, much work has been devoted to developing a framework for understanding the complex nature of this phenomenon as well as discovering its utility in various applications. The main effort of this dissertation is to develop a WLC for the purpose of broadband nonlinear spectroscopy and use it in spectroscopic measurements. The ability to generate a high-quality, high-spectral-irradiance source of radiation confined in a single beam that spans the visible and near-infrared spectral regimes has great utility for nonlinear measurement methods such as the Z-scan technique. Using a broadband WLC instead of conventional tunable sources of radiation such as optical parametric generators/amplifiers has been shown to increase the efficiency of such measurements by nearly an order of magnitude. Although WLC generation has many complex processes involved, and complete models of the process involve highly complex numerical modeling, simple models can still guide us in the optimization of systems for WLC generation. In this dissertation the effects of two key mechanisms behind WLC generation in gaseous media are explored: self-phase modulation (SPM) and ionization leading to plasma production. The effects of SPM are largely dependent upon the third-order nonlinear refractive index, n2, of the gaseous medium whereas the effects of plasma production are dependent upon many parameters including the initial number density, ionization potential/energy, and the rate of ionization production. It is found that in order to generate a stable WLC suitable for nonlinear spectroscopy, the phase contributions from SPM and plasma production should be nearly equal. This guided our experiments in inert gases using mJ level, 150 fs-FWHM (full-width at half-maximum) pulses at 780 nm as well as 40 fs-FWHM pulses primarily at 1800 nm to create a stable, high-spectral-irradiance WLC. The generated WLC is shown to have sufficient spectral energy and spatial quality suitable for nonlinear spectroscopic measurements. In addition to extending the WLC bandwidth by using a long wavelength (1800 nm) pump source, it is found that by using a secondary weak seed pulse with a peak irradiance three orders of magnitude less than the main pulse, the spectral energy density is enhanced by more than a factor of 3 in Krypton gas for a WLC spectrum that spans over 2 octaves. Numerical simulations are presented which qualitatively describe the experimental results. The spectral enhancement of the WLC by seeding is also demonstrated for other inert gases and condensed media. Other efforts described in this dissertation include the development of the Dual-Arm Z-scan technique and its extension to measuring thin film nonlinearities in the presence of large substrate signals as well as predicting the n2 spectra of organic molecules (where we can approximate their behavior as if they were centrosymmetric) from knowledge of the one-photon and two-photon absorption spectra using a simplified sum-over-states quantum perturbative model by utilizing a quasi 3-level and quasi 4-level system.
Show less - Date Issued
- 2015
- Identifier
- CFE0005608, ucf:50264
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005608
- Title
- Design Optimization of LLC Topology and Phase Skipping Control of Three Phase Inverter for PV Applications.
- Creator
-
Somani, Utsav, Batarseh, Issa, Wu, Xinzhang, Seyedi-Esfahani, Seyed-alireza, University of Central Florida
- Abstract / Description
-
The world is heading towards an energy crisis and desperate efforts are being made to find an alternative, reliable and clean source of energy. Solar Energy is one of the most clean and reliable source of renewable energy on earth. Conventionally, extraction of solar power for electricity generation was limited to PV farms, however lately Distributed Generation form of Solar Power has emerged in the form of residential and commercial Grid Tied Micro-Inverters. Grid Tied Micro-Inverters are...
Show moreThe world is heading towards an energy crisis and desperate efforts are being made to find an alternative, reliable and clean source of energy. Solar Energy is one of the most clean and reliable source of renewable energy on earth. Conventionally, extraction of solar power for electricity generation was limited to PV farms, however lately Distributed Generation form of Solar Power has emerged in the form of residential and commercial Grid Tied Micro-Inverters. Grid Tied Micro-Inverters are costly when compared to their string type counterparts because one inverter module is required for every single or every two PV panels whereas a string type micro-inverter utilizes a single inverter module over a string of PV panels. Since in micro-inverter every panel has a dedicated inverter module, more power per panel can be extracted by performing optimal maximum power tracking over single panel rather than over an entire string of panels. Power per panel extracted by string inverters may be lower than its maximum value as few of the panels in the string may or may not be shaded and thereby forming the weaker links of the system.In order to justify the higher costs of Micro-Inverters, it is of utmost importance to convert the available power with maximum possible efficiency. Typically, a micro-inverter consists of two important blocks; a Front End DC-DC Converter and Output DC-AC Inverter. This thesis proposes efficiency optimization techniques for both the blocks of the micro-inverter. Efficiency Optimization of Front End DC-DC Converter-This thesis aims to optimize the efficiency of the front end stage by proposing optimal design procedure for resonant parameters of LLC Topology as a Front End DC-DC Converter for PV Applications. It exploits the I-V characteristics of a solar panel to design the resonant parameters such that resonant LLC topology operates near its resonant frequency operating point which is the highest efficiency operating point of LLC Converter.Efficiency Optimization of Output DC-AC Inverter-Due to continuously variable irradiance levels of solar energy, available power for extraction is constantly varying which causes the PV Inverter operates at its peak load capacity for less than 15% of the day time. Every typical power converter suffers through poor light load efficiency performance because of the load independent losses present in a power converter. In order to improve the light load efficiency performance of Three Phase Inverters, this thesis proposes Phase Skipping Control technique for Three Phase Grid Tied Micro-Inverters. The proposed technique is a generic control technique and can be applied to any inverter topology, however, in order to establish the proof of concept this control technique has been implemented on Three Phase Half Bridge PWM Inverter and its analysis is provided. Improving light load efficiency helps to improve the CEC efficiency of the inverter.
Show less - Date Issued
- 2013
- Identifier
- CFE0005265, ucf:50573
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005265
