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Title: EFFECTS OF ISOLATION ON METAPOPULATIONDYNAMICS IN SMALL-WORLD NETWORKS.
Creator: Bernard, Alaina, Jenkins, David, University of Central Florida
Abstract / Description: Simulation models are valuable for making predictions that may be tested in natural systems and for understanding observed patterns. The simulation model developed for this thesis evaluates the effects of spatial network architecture, including organism dispersal patterns and isolation of habitats, on metapopulations. Two fields were merged throughout this project: metapopulation biology and small-world network theory. Small-world networks are characterized in their extremes as scale-free or...
Show moreSimulation models are valuable for making predictions that may be tested in natural systems and for understanding observed patterns. The simulation model developed for this thesis evaluates the effects of spatial network architecture, including organism dispersal patterns and isolation of habitats, on metapopulations. Two fields were merged throughout this project: metapopulation biology and small-world network theory. Small-world networks are characterized in their extremes as scale-free or single-scale. These models potentially simulate the networks of habitats and corridors in which metapopulations operate. Small-world network theory has been used to describe systems as diverse as rivers, the world-wide-web, and protein interactions, but has not been used as an experimental treatment for metapopulation dynamics. I tested the effects of growth rate, dispersal pattern, network architecture (scale-free and single-scale), attack type (targeted or random), and attack severity (0, 5, 10, 20, or 40% attacked populations) on metapopulation size and inter-population variation in a simulated system designed to be relevant to conservation biology and ecology. Metapopulation size and inter-population variation changed due to combinations of dispersal pattern, growth rate, and attack severity. Specifically, metapopulations were most affected by a combination of unidirectional dispersal and low growth rate in both metapopulation number and inter-population variation. However, a significant difference between scale-free and single-scale metapopulations was not found due to a low connectivity in the modeled networks as well as limitations of experimental assumptions. However, future studies that alter the model's assumptions could improve understanding of the influence of landscape structure on at-risk metapopulations.
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Date Issued: 2007
Identifier: CFE0001877, ucf:47384
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001877

Title: Vulture Scavenging of Child-sized Pig Carcasses in Central Florida: Utilizing GIS to Analyze Site Variables Affecting Skeletal Dispersal.
Creator: Mitchell, Alexander, Schultz, John, Williams, Lana, Dupras, Tosha, University of Central Florida
Abstract / Description: Scavengers can significantly alter a forensic scene and consume, modify, disarticulate, and disperse bodies. However, little research exists regarding scavenging in Central Florida, specifically scavenging involving Black and Turkey Vultures (Coragyps atratus, Cathartes aura respectively). The purpose of this study is to examine the effects of vulture scavenging on consumption, disarticulation, and dispersal of child-sized carcasses in the Central Florida region. The research sample consisted...
Show moreScavengers can significantly alter a forensic scene and consume, modify, disarticulate, and disperse bodies. However, little research exists regarding scavenging in Central Florida, specifically scavenging involving Black and Turkey Vultures (Coragyps atratus, Cathartes aura respectively). The purpose of this study is to examine the effects of vulture scavenging on consumption, disarticulation, and dispersal of child-sized carcasses in the Central Florida region. The research sample consisted of four pig (Sus scrofa) carcasses weighing approximately 25kgs that were deposited in two distinct sites (shaded and unshaded) at the Deep Foundations Geotechnical Research Site located on the UCF campus. Two field cameras were placed at each site to record the scavenging, decomposition, and dispersal. The dispersal data was mapped and analyzed using ArcGIS v. 10.2.2 spatial analyst tools. Additionally, the scavengers recorded during the research period were noted, and their effect on disarticulation, consumption and dispersal were analyzed. Overall, while the canopy at the shaded sites did not impact vulture scavenging, grass height, the site perimeter fence, and the ground surface foliage density impacted vulture dispersal patterns. The majority of elements were dispersed within 6m of the initial carcass deposition. Through analysis of recorded video it was determined that vultures were able to completely skeletonize a child-sized carcass in approximately 8 hours of feeding time. In addition to vulture activity, opossums were recorded further dispersing and modifying skeletal remains after vulture activity had ceased.
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Date Issued: 2016
Identifier: CFE0006358, ucf:51498
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006358

Title: THE ROLE OF THE FERAL PIG (SUS SCROFA) AS A DISTURBANCE AGENT AND SEED DISPERSER IN CENTRAL FLORIDA'S NATURAL LANDS.
Creator: Brescacin, Camille, Jenkins, David, University of Central Florida
Abstract / Description: Feral pigs (Sus scrofa) are considered to be among the world's worst invasive species due to their successful invasion and ecological and economic impact to native and agricultural plants and animals around the world. Feral pigs are significant disturbance agents that destroy plant communities, change soil characteristics, alter nutrient cycling, and create open sites for colonization of both native and non-native plant species through their foraging behavior called rooting. In contrast to...
Show moreFeral pigs (Sus scrofa) are considered to be among the world's worst invasive species due to their successful invasion and ecological and economic impact to native and agricultural plants and animals around the world. Feral pigs are significant disturbance agents that destroy plant communities, change soil characteristics, alter nutrient cycling, and create open sites for colonization of both native and non-native plant species through their foraging behavior called rooting. In contrast to native animal disturbances, rooting is a striking feature in the landscape that varies in space, seasonal timing, frequency (number of times rooted), and intensity (depth of rooting). During this study, feral pigs rooted 7.7% of the search area, which increased to 12% when abandoned patches (baseline patches that were not rooted during this study) were included. Overall, feral pigs rooted and re-rooted habitats along roads and trails significantly more than wetlands. Rooting also varied temporally with the most rooting occurring during July-November, which also corresponds to the peak in rooting intensity. Implications to land managers include avoiding the installation of roads and trails near wet to mesic habitats or other habitats that contain species of concern in order to conserve habitat quality and recreational value. Despite less rooting activity, feral pigs still pose a significant threat to wetlands as evidenced by the large amount of abandoned patches documented. In order to conserve natural areas, effective management and development of efficient control methods is needed to keep feral pig populations in check. As a large opportunistic omnivore, feral pigs have the potential to be important vectors for endozoochorus seed dispersal of a variety of plant species. Feral pigs can travel long distances and have a gut retention time up to 49 hours, therefore seeds can be deposited throughout the landscape far from the parent plant. Over the course of this study, feral pigs dispersed 50 plant species from a wide range of ecological and morphological characteristics, though the majority were native, small seeded, wetland species. For most plant species, location of deposition matched their habitat preference and suggests a high probability of survival. Feral pigs disperse mainly wetland plant species, which has important implications for wetland conservation. However, feral pigs also deposited unwanted species into wetlands and predated the seeds of important wetland canopy tree species.
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Date Issued: 2010
Identifier: CFE0003468, ucf:48934
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003468

Title: DISPERSAL BEHAVIOR OF MOSQUITOFISH (GAMBUSIA HOLBROOKI).
Creator: Alemadi, Shireen, Jenkins, David, University of Central Florida
Abstract / Description: Mosquitofish (Gambusia holbrooki) are native to the southeastern United States but invasive elsewhere, and are dominant predators in many ecosystems that they inhabit. Information on dispersal behavior will help better understand and predict mosquitofish metapopulation dynamics and invasions. I experimentally tested dispersal behavior of individual mosquitofish under a range of laboratory conditions relevant to field situations. Preliminary experiments showed that gender, lighting conditions,...
Show moreMosquitofish (Gambusia holbrooki) are native to the southeastern United States but invasive elsewhere, and are dominant predators in many ecosystems that they inhabit. Information on dispersal behavior will help better understand and predict mosquitofish metapopulation dynamics and invasions. I experimentally tested dispersal behavior of individual mosquitofish under a range of laboratory conditions relevant to field situations. Preliminary experiments showed that gender, lighting conditions, hunger and acclimation time did not significantly affect net dispersal rate. Power analysis based on this preliminary experiment determined that 6 replicate fish were sufficient for each subsequent experiment; I used 24 fish, and each fish was tested one time. Three factors that potentially could affect net swimming rate were tested: habitat of origin (permanent vs. temporary waters), water depth (3-24 mm), and the interaction between water depth and leaf litter type (upland and wetland). Fish from a temporary pond dispersed significantly faster than fish from a permanent pond, and fish dispersed significantly faster in deeper water than in shallower water. However, leaf litter significantly inhibited fish dispersal at all depths tested. Based on these experiments, G. holbrooki disperse more readily through relatively open and deeper (several centimeters) pathways between habitats such as roadside ditches, drainage canals and trails in flooded conditions. My results are useful for understanding mosquitofish dispersal behavior based on the abiotic and biotic factors examined in this experiment. I predict that mosquitofish can spread from a point of introduction at about 800 m per day, given and unobstructed path of only > 6 mm depth.
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Date Issued: 2006
Identifier: CFE0001001, ucf:46836
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001001

Title: VERIFICATION OF FAA'S EMISSIONS AND DISPERSION MODELING SYSTEM (EDMS).
Creator: Martin, Anjoli, Wayson, Roger, University of Central Florida
Abstract / Description: Air quality has been a major environmental concern for many years. Recently the issue of airport emissions has presented growing concerns and is being studied in much more depth. Airport emissions come from a variety of point, line and area sources, making emissions modeling for airports very complex and more involved. Accurate air quality models, specific to airport needs, are required to properly analyze this complex array of air pollution sources created by airports. Accurate air quality...
Show moreAir quality has been a major environmental concern for many years. Recently the issue of airport emissions has presented growing concerns and is being studied in much more depth. Airport emissions come from a variety of point, line and area sources, making emissions modeling for airports very complex and more involved. Accurate air quality models, specific to airport needs, are required to properly analyze this complex array of air pollution sources created by airports. Accurate air quality models are needed to plan for increased growth of current airports and address concerns over proposed new ones. The Federal Aviation Administration's (FAA) Emissions and Dispersion Modeling System (EDMS) is a program that is the required model for assessing emissions from airport sources. This research used EDMS Version 4.21, which incorporates the EPA dispersion model AERMOD, to model detailed airport data and compare the model's predicted values to the actual measured carbon monoxide concentrations at 25 locations at a major U.S. airport. Statistics relating the model characteristics as well as trends are presented. In this way, a thorough investigation of the accuracy of the EDMS modeled values of carbon monoxide was possible. EDMS modeling included two scenarios, the first scenario referred to as practice detail included general airport information that a modeler could find from the airport being studied and the second scenario referred to as research detail utilized very detailed information from observer logs during a three day observation period. Each of the modeling scenarios was compared to the field measured data and to each other. These comparisons are important to insure the model is adequately describing emissions sources at airports. Data analysis of this study was disappointing since measured levels of CO were generally higher than modeled values. Since EDMS is continually changing and improving perhaps these results can help enhance future models.
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Date Issued: 2006
Identifier: CFE0001282, ucf:46903
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001282

Title: STABILITY AND PRESERVATION PROPERTIES OF MULTISYMPLECTIC INTEGRATORS.
Creator: Wlodarczyk, Tomasz, Schober, Constance, University of Central Florida
Abstract / Description: This dissertation presents results of the study on symplectic and multisymplectic numerical methods for solving linear and nonlinear Hamiltonian wave equations. The emphasis is put on the second order space and time discretizations of the linear wave, the Klein-Gordon and the sine-Gordon equations. For those equations we develop two multisymplectic (MS) integrators and compare their performance to other popular symplectic and non-symplectic numerical methods. Tools used in the linear analysis...
Show moreThis dissertation presents results of the study on symplectic and multisymplectic numerical methods for solving linear and nonlinear Hamiltonian wave equations. The emphasis is put on the second order space and time discretizations of the linear wave, the Klein-Gordon and the sine-Gordon equations. For those equations we develop two multisymplectic (MS) integrators and compare their performance to other popular symplectic and non-symplectic numerical methods. Tools used in the linear analysis are related to the Fourier transform and consist of the dispersion relationship and the power spectrum of the numerical solution. Nonlinear analysis, in turn, is closely connected to the temporal evolution of the total energy (Hamiltonian) and can be viewed from the topological perspective as preservation of the phase space structures. Using both linear and nonlinear diagnostics we find qualitative differences between MS and non-MS methods. The first difference can be noted in simulations of the linear wave equation solved for broad spectrum Gaussian initial data. Initial wave profiles of this type immediately split into an oscillatory wave-train with the high modes traveling faster (MS schemes), or slower (non-MS methods), than the analytic group velocity. This result is confirmed by an analysis of the dispersion relationship, which also indicates improved qualitative agreement of the dispersive curves for MS methods over non-MS ones. Moreover, observations of the convergence patterns in the wave profile obtained for the sine-Gordon equation for the initial data corresponding to the double-pole soliton and the temporal evolution of the Hamiltonian functional computed for solutions obtained from different discretizations suggest a change of the geometry of the phase space. Finally, we present some theoretical considerations concerning wave action. Lagrangian formulation of linear partial differential equations (PDEs) with slowly varying solutions is capable of linking the wave action conservation law with the dispersion relationship thus suggesting the possibility to extend this connection to multisymplectic PDEs.
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Date Issued: 2007
Identifier: CFE0001817, ucf:47344
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001817

Title: DIRECT NONLINEAR OPTICS MEASUREMENTS OF RAMAN GAIN IN BULK GLASSES AND ESTIMATES OF FIBER PERFORMANCE.
Creator: Stegeman, Robert, Delfyett, Peter, University of Central Florida
Abstract / Description: The need for more bandwidth in communications has stimulated the search for new fiberizable materials with properties superior to fused silica which is the current state-of-the-art. One of the key properties is Raman gain by which a pump beam amplifies a signal beam of longer wavelength. An apparatus capable of directly measuring the spectral dependence and absolute magnitude of the material Raman gain coefficient using nonlinear optics techniques has been built. Using radiation from a 1064...
Show moreThe need for more bandwidth in communications has stimulated the search for new fiberizable materials with properties superior to fused silica which is the current state-of-the-art. One of the key properties is Raman gain by which a pump beam amplifies a signal beam of longer wavelength. An apparatus capable of directly measuring the spectral dependence and absolute magnitude of the material Raman gain coefficient using nonlinear optics techniques has been built. Using radiation from a 1064 nm Nd:YAG laser as the pump and from a tunable Optical Parametric Generator and Amplifier as the signal, the Raman gain spectrum was measured for different families of glass samples with millimeter thickness. A number of glass families were investigated. Tellurites with added oxides of tungsten, niobium, and thallium produced the largest Raman gain coefficients of any oxide family reported to date, typically 30-50 times higher than that of fused silica. On the other hand, phosphate families were found with spectrally broad Raman gain response, 5 times broader than fused silica and flat to „b3dB over the full spectral range in some compositions. Although the chalcogenides were found to photodamage easily, coefficients 50 - 80 times that of fused silica were measured. Finally, a numerical study was undertaken to predict the theoretical performance and noise properties of tellurite fibers for communications. Included in the computer modeling were linear loss; the interaction among multiple pumps and signals; forward and/or backward propagating pump beams; forward, backward and double Rayleigh scattering; noise properties of amplifiers; excess noise, etc. This led to a comparison of the optical signal-to-noise characteristics for Raman gain in a tellurite versus a silica fiber.
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Date Issued: 2006
Identifier: CFE0000928, ucf:46739
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000928

Title: HYBRID CARBON FIBER ALUMINA NANOCOMPOSITE FOR NON-CONTACT STRESS SENSING VIA PIEZOSPECTROSCOPY.
Creator: Hanhan, Imad, Raghavan, Seetha, University of Central Florida
Abstract / Description: Carbon fiber composites have become popular in aerospace structures and applications due to their light weight, high strength, and high performance. Recently, scientists have begun investigating hybrid composites that include fibers and particulate fillers, since they allow for advanced tailoring of mechanical properties, such as improved fatigue life. This project investigated a hybrid carbon fiber reinforced polymer (HCFRP) that includes carbon fiber and additional alumina nanoparticle...
Show moreCarbon fiber composites have become popular in aerospace structures and applications due to their light weight, high strength, and high performance. Recently, scientists have begun investigating hybrid composites that include fibers and particulate fillers, since they allow for advanced tailoring of mechanical properties, such as improved fatigue life. This project investigated a hybrid carbon fiber reinforced polymer (HCFRP) that includes carbon fiber and additional alumina nanoparticle fillers, which act as embedded nano stress-sensors. Utilizing the piezospectroscopic effect, the photo-luminescent spectral signal of the embedded nanoparticles has been monitored as it changes with stress, enabling non-contact stress detection of the material. The HCRFP's stress-sensitive properties have been investigated in-situ using a laser source and a tensile mechanical testing system. Hybrid composites with varying mass contents of alumina nanoparticles have been studied in order to determine the effect of particle content on the overall stress sensing properties of the material. Additionally, high resolution photo-luminescent maps were conducted of the surfaces of each sample in order to determine the particulate dispersion of samples with varying alumina content. The dispersion maps also served as a method of quantifying particulate sedimentation, and can aid in the improvement of the manufacturing process. The results showed that the emitted photo-luminescent spectrum can indeed be captured from the embedded alumina nanoparticles, and exhibits a systematic trend in photo-luminescent peak shift with respect to stress. The stress maps showed a linear increase in peak shift up to a certain critical stress, and matched closely with the DIC strain results. Therefore, the non-contact stress sensing results shown in this work have strong implications for the future of structural health monitoring and nondestructive evaluation (NDE) of aerospace structures.
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Date Issued: 2015
Identifier: CFH0004750, ucf:45384
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004750

Title: PREDICTING AIR QUALITY NEAR ROADWAY INTERSECTIONS THROUGH THE APPLICATION OF A GAUSSIAN PUFF MODEL TO MOVING SOURCES.
Creator: Kim, Brian, Wayson, Roger, University of Central Florida
Abstract / Description: With substantial health and economic impacts attached to many highway-related projects, it has become imperative that the models used to assess air quality be as accurate as possible. The United States (US) Environmental Protection Agency (EPA) currently promulgates the use of CAL3QHC to model concentrations of carbon monoxide (CO) near roadway intersections. This model uses steady-state and macroscopic methods to model the physical phenomena (e.g., emission rates, atmospheric dispersion, etc...
Show moreWith substantial health and economic impacts attached to many highway-related projects, it has become imperative that the models used to assess air quality be as accurate as possible. The United States (US) Environmental Protection Agency (EPA) currently promulgates the use of CAL3QHC to model concentrations of carbon monoxide (CO) near roadway intersections. This model uses steady-state and macroscopic methods to model the physical phenomena (e.g., emission rates, atmospheric dispersion, etc.) occurring at intersections. These methods are not straightforward and unintuitive for the users. Therefore, this project investigated the possibility of developing a model that is theoretically more realistic and flexible than CAL3QHC. The new model entitled, Traffic Air Quality Simulation Model (TRAQSIM), uses a microscopic approach by modeling vehicle movements and dispersion in a simulation environment. Instead of steady-state plume equations used in the CAL3QHC model, TRAQSIM uses a discrete puff methodology that can be used to model time-based dispersion of pollutants. Most of the components incorporated into TRAQSIM have been drawn from existing methodologies and therefore, are not new. However, the combination of these different methods into a single integrated model is new and presents a novel approach to such a model. Initial verification and sensitivity/trend studies of the model indicate that TRAQSIM uses reasonable/realistic traffic parameters and behaves intuitively correct. A validation study showed that TRAQSIM produces good results when compared to actual measured data with an overall R2 value of 0.605 for 11 scenarios comprising 264 data points. Although most statistical parameters showed CAL3QHC agrees better overall with measured data (R2 value of 0.721), the comparisons were mixed on a scenario-by-scenario basis; that is, CAL3QHC showed better results for 6 scenarios and TRAQSIM showed better results for 5 scenarios. Additional tests with larger datasets, which were beyond the scope of this work, could be conducted to obtain more definitive conclusions and allow further development of TRAQSIM. While CAL3QHC is a mature model that has been developed over many years, TRAQSIM is new and has much more potential for improvement. The physical parameters used in TRAQSIM allow it to be more directly (more logically) improved than the approximations used in CAL3QHC. In addition, although the fundamental-level modeling in TRAQSIM make it a more complex model internally, it is much more intuitive for the user to understand and use.
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Date Issued: 2004
Identifier: CFE0000316, ucf:46306
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000316

Title: DESIGN AND OPTIMIZATION OF NANOSTRUCTURED OPTICAL FILTERS.
Creator: Brown, Jeremiah, Moharam, Jim, University of Central Florida
Abstract / Description: 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...
Show moreOptical 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 complicated conversions between optical and electrical signals. This dissertation explores three classes of nano-scale optical filters in an effort to obtain different types of dispersive response functions. First, dispersive waveguides are designed using a sub-wavelength periodic structure to transmit a single TE propagating mode with very high second order dispersion. Next, an innovative approach for decoupling waveguide trajectories from Bragg gratings is outlined and used to obtain a uniform second-order dispersion response while minimizing fabrication limitations. Finally, high Q-factor microcavities are coupled into axisymmetric pillar structures that offer extremely high group delay over very narrow transmission bandwidths. While these three novel filters are quite diverse in their operation and target applications, they offer extremely compact structures given the magnitude of the dispersion or group delay they introduce to an incident signal. They are also designed and structured as to be formed on an optical wafer scale using standard integrated circuit fabrication techniques. A number of frequency-domain numerical simulation methods are developed to fully characterize and model each of the different filters. The complete filter response, which includes the dispersion and delay characteristics and optical coupling, is used to evaluate each filter design concept. However, due to the complex nature of the structure geometries and electromagnetic interactions, an iterative optimization approach is required to improve the structure designs and obtain a suitable response. To this end, a Particle Swarm Optimization algorithm is developed and applied to the simulated filter responses to generate optimal filter designs.
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Date Issued: 2008
Identifier: CFE0002502, ucf:47678
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002502

Title: PHASE AND AMPLITUDE MODULATED OFDM FOR DISPERSION MANAGED WDM SYSTEMS.
Creator: Eisele, Andreas, Li, Guifang, University of Central Florida
Abstract / Description: 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...
Show moreAmplitude 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 aging. OFDM is inherently tolerant to over- or under-compensation and dispersion slope mismatch. OFDM transmission over dispersive, non-dispersion managed fiber links using OFDM requires an overhead in excess of the maximum accumulated dispersion. Existing WDM systems usually employ periodic dispersion management. OFDM in these systems requires a smaller overhead. It is, however, more susceptible to nonlinearity due to the coherent beating of subcarriers after each dispersion-compensated span. The large variation in intensity associated with amplitude-modulated OFDM makes this modulation format more susceptible to nonlinear effects in fiber compared to phase-modulated signals. This holds true unless dispersion and EDFA noise lead to amplitude variations strong enough for PM-OFDM to be degraded by nonlinear effects as well. In conclusion OFDM is beneficial for non-ideal dispersion managed systems. PM-OFDM can further improve the performance.
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Date Issued: 2008
Identifier: CFE0002492, ucf:47682
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002492

Title: CHARACTERIZATION OF DISPERSION AND RESIDUAL STRESS IN NANOPARTICLE REINFORCED HYBRID CARBON FIBER COMPOSITES.
Creator: Selimov, Alex, Raghavan,Seetha, University of Central Florida
Abstract / Description: Hybrid carbon fiber reinforced composites are a new breed of materials that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties and stress sensing capabilities can be achieved. In order to maximize these properties, it is necessary to achieve a homogeneous dispersion of particulate filler. Utilizing the...
Show moreHybrid carbon fiber reinforced composites are a new breed of materials that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties and stress sensing capabilities can be achieved. In order to maximize these properties, it is necessary to achieve a homogeneous dispersion of particulate filler. Utilizing the photoluminescent properties of alumina, it is possible to compare local levels of particle concentration through emission intensities as a way to determine the effectiveness of the tested manufacturing parameters in increasing material homogeneity. Parameters of these photoluminescence emissions have been established to be stress dependent, which allows for in situ residual stress measurements. It is shown here that the application of silane coupling agents as particle surface treatments improves particle dispersion when compared to untreated samples. Reactive silane coupling agent (RSCA) treatments were found to provide for greater dispersion improvements when compared to non-reactive silane coupling agents (NRSCA). Higher resolution investigations into these samples found that treatment with a reactive coupling agent altered the stress state of particles concentrated around the fiber from a tensile stress state to a compressive stress state. This is proposed to result from bonding of the reactive groups on the coupling agent to the organic groups on the carbon fibers which adjusts the stress state of the particle. Future mechanical tests will verify the effects of the particle surface functionalization treatments on mechanical properties of the composites.
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Date Issued: 2016
Identifier: CFH0000233, ucf:44669
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0000233

Title: DETERMINING FLORIDA LANDFILL ODOR BUFFER DISTANCES USING AERMOD.
Creator: Figueroa, Veronica, Cooper, C. David, University of Central Florida
Abstract / Description: As U.S. landfills continue to grow in size, concerns about odorous gas emissions from landfills are increasing. For states that are expanding in population, such as Florida, odors from landfills are a major concern because new housing developments, needed to accommodate the rapid population growth, are creeping closer and closer to the existing landfills. As homes get closer to landfills, odor complaints are likely to become more frequent, causing landfill managers increased problems with...
Show moreAs U.S. landfills continue to grow in size, concerns about odorous gas emissions from landfills are increasing. For states that are expanding in population, such as Florida, odors from landfills are a major concern because new housing developments, needed to accommodate the rapid population growth, are creeping closer and closer to the existing landfills. As homes get closer to landfills, odor complaints are likely to become more frequent, causing landfill managers increased problems with public interactions. Odor buffer zones around landfills need to be established to give municipalities tools to help prevent the building of future homes too close to landfills. Using the latest air dispersion model, AERMOD, research predicted downwind odor concentrations from a Central Florida landfill. Accurate estimates of methane emissions throughout a Central Florida landfill were determined using a new technique developed as part of this research that uses hundreds of ambient air VOC measurements taken within a landfill, as receptors. Hundreds of point sources were placed on the landfill, and the standard Gaussian dispersion equations were solved by matrix inversion methods. The methane emission rates were then used as surrogates for odor emissions to predict downwind odor concentrations via AERMOD. By determining a critical zone around a landfill with regards to odor, stakeholders will be able to meet regulatory issues and assist their communities. Other beneficial uses from this research include: determination of existing gas collection system efficiencies, calculation of fugitive greenhouse gas emissions from municipal solid waste (MSW) landfills, and improved landfill gas management.
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Date Issued: 2008
Identifier: CFE0002200, ucf:47910
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002200

Title: HYDROGEN SULFIDE FLUX MEASUREMENTS AND DISPERSION MODELING FROM CONSTRUCTION AND DEMOLITION (C&D) DEBRIS LANDFILLS.
Creator: Eun, Sangho, Reinhart, Debra, University of Central Florida
Abstract / Description: Odor problems are a common complaint from residents living near landfills. Many compounds can cause malodorous conditions. However, hydrogen sulfide (h2s) has been identified as a principal odorous component from construction and demolition (c&d)debris landfills. Although several studies have reported the ambient concentrations of h2s near c&d landfills, few studies have quantified emission rates of h2s. The most widely used and proven technique for measuring gas emission rates from...
Show moreOdor problems are a common complaint from residents living near landfills. Many compounds can cause malodorous conditions. However, hydrogen sulfide (h2s) has been identified as a principal odorous component from construction and demolition (c&d)debris landfills. Although several studies have reported the ambient concentrations of h2s near c&d landfills, few studies have quantified emission rates of h2s. The most widely used and proven technique for measuring gas emission rates from landfills is the flux chamber method. Typically the flux chamber is a cylindrical enclosure device with a spherical top which limits the gas emission area. Pure zero grade air is introduced into the chamber, allowed to mix with emitting gases captured from the landfill surface, and then transported to the exit port where concentrations can be measured. Flux measurements using the flux chamber were performed at five different c&d landfills from june to august, 2003. The flux rates of h2s measured in this research were three to six orders of magnitude lower than the flux rates of methane reported in the literature. In addition to the h2s flux measurements, dispersion modeling was conducted, using the epa dispersion model, industrial source complex short term (iscst3), in order to evaluate impacts on landfill workers and communities around the landfills. The modeling results were analyzed to estimate the potential ground level maximum h2s concentrations for 1-hr and 3-min periods and the frequency (occurrences per year) above the h2s odor detection threshold for each landfill. Odor complaints could be expected from four among five landfills selected for this study, based on 0.5-ppb odor detection threshold.
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Date Issued: 2004
Identifier: CFE0000169, ucf:52837
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000169

Title: Does the journey matter more than the destination? The contribution of geospatial characteristics and local variables to invasive Pomacea maculata distribution across ranchland wetlands.
Creator: Pierre, Steffan, Quintana-Ascencio, Pedro, Jenkins, David, Boughton, Elizabeth, University of Central Florida
Abstract / Description: Geospatial characteristics such as isolation and avenues of connectivity influence an invader's pattern of dispersal and distribution. However many examinations of invasion success ignore the contribution of dispersal to patterns of invasion and focus only on the local environmental/habitat factors. This study examines the interaction of geospatial characteristics, that may influence dispersal, and local environmental factors, that may govern successful occupation, on the likelihood of...
Show moreGeospatial characteristics such as isolation and avenues of connectivity influence an invader's pattern of dispersal and distribution. However many examinations of invasion success ignore the contribution of dispersal to patterns of invasion and focus only on the local environmental/habitat factors. This study examines the interaction of geospatial characteristics, that may influence dispersal, and local environmental factors, that may govern successful occupation, on the likelihood of invasion (invasability) of wetlands within an agriculturally modified landscape. I examined the current invasion of seasonal wetlands in south-central Florida ranchland by non-native apple snails (Pomacea maculata (Ampullariidae)) as a model system for understanding this interaction. I surveyed spatial occurrence of P. maculata in 171 wetlands in 2014 and found they occurred in 43% of wetlands surveyed. I evaluated how occurrence was related to geospatial variables (proximity to propagule sources, shoreline complexity, interwetland distance, elevation, area and ditch presence) and wetland characteristics (pH, water hardness, conductivity and soil type) for 95 wetlands. Presence of ditch connections and more neutral water pH were associated with P. maculata occurrence. I did not find evidence that Euclidean distance and minimum ditch distance were associated with P. maculata occurrence. I also performed a 5 month field experiment where I translocated snails to previously occupied and non-occupied wetlands and measured snail survival and growth (20 wetlands from November to March). This experiment evaluated if non-occurrence during survey was more likely to be associated with unfavorable habitat conditions or dispersal limitation. Wetland pH and water hardness explained variation in P. maculata survival, and wetland pH best explained growth. I did not find evidence that prior occupancy affected the snail survival and growth, which suggests previously unoccupied wetlands are due to dispersal limitation. These results emphasize that man-made conduits can increase permeability of the landscape, facilitating the dispersal and introduction of nonnative species and the need for the inclusion of dispersal metrics in understanding invasive species distribution.
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Date Issued: 2015
Identifier: CFE0006374, ucf:51527
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006374

Title: Near-road Dispersion Modeling of Mobile Source Air Toxics (MSATs) in Florida.
Creator: Westerlund, Kurt, Cooper, Charles, Radwan, Ahmed, Randall, Andrew, Hall, Steven, University of Central Florida
Abstract / Description: There is a growing public concern that emissions of mobile source air toxics (MSATs) from motor vehicles may pose a threat to human health. At present, no state or federal agencies require dispersion modeling of these compounds, but many agencies are concerned about potential future requirements. Current air pollution professionals are familiar with Federal Highway Administration (FHWA) and U.S. Environmental Protection Agency (EPA) requirements for dispersion modeling to produce predicted...
Show moreThere is a growing public concern that emissions of mobile source air toxics (MSATs) from motor vehicles may pose a threat to human health. At present, no state or federal agencies require dispersion modeling of these compounds, but many agencies are concerned about potential future requirements. Current air pollution professionals are familiar with Federal Highway Administration (FHWA) and U.S. Environmental Protection Agency (EPA) requirements for dispersion modeling to produce predicted concentrations for comparison with appropriate standards. This research examined a method in which the potential near-road concentrations of MSATs were calculated. It was believed that by assessing MSATs in much the same way that are used for other pollutants, the model and methods developed in this research could become a standard for those quantifying MSAT concentrations near-roadways.This dissertation reports on the results from short-term (1-hour) and long-term (annual average) MSATs dispersion modeling that has been conducted on seven intersections and seven freeway segments in the state of Florida. To accomplish the modeling, the CAL3QHC model was modified to handle individual MSAT emissions input data and to predict the concentrations of several MSATs around these roadway facilities. Additionally, since the CAL3MSAT model is DOS based and not user-friendly, time was invested to develop a Windows(&)#174; graphical user interface (GUI). Real-world data (traffic volumes and site geometry) were gathered, worst-case meteorology was selected, mobile source emission factors (EFs) were obtained from MOVES2010a, and worst-case modeling was conducted. Based on a literature search, maximum acceptable concentrations (MACs) were proposed for comparison with the modeled results, for both a short-term (1-hour) averaging time and a long-term (1-year) averaging time.Results from this CAL3MSAT modeling study indicate that for all of the intersections and freeway segments, the worst-case 1-hour modeled concentrations of the MSATs were several orders of magnitude below the proposed short-term MACs. The worst-case 1-year modeled concentrations were of the same order of magnitude as the proposed long-term MACs.The 1-year concentrations were first developed by applying a persistence factor to the worst-case 1-hour concentrations. In the interest of comparing the predicted concentrations from the CAL3MSAT persistence factor approach to other dispersion models, two EPA regulatory models (CAL3QHCR and AERMOD) with the ability to account for yearly meteorology, traffic, and signal timing were used. Both hourly and annual MSAT concentrations were predicted at one large urban intersection and compared for the three different dispersion models. The short-term 1-hour results from CAL3MSAT were higher than those predicted by the two other models due to the worst-case assumptions. Similarly, results indicate that the CAL3MSAT persistence factor approach predicted a worst-case annual average concentration on the same order of magnitude as the two other more refined models. This indicated that the CAL3MSAT model might be useful as a worst-case screening approach.
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Date Issued: 2013
Identifier: CFE0004772, ucf:49804
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004772

Title: Juvenile Ornamentation: Its Evolution, Genetic Basis, and Variation Across Habitats.
Creator: Tringali, Angela, Noss, Reed, Bowman, Reed, Fauth, John, Fedorka, Kenneth, University of Central Florida
Abstract / Description: Ornamental traits are considered honest advertisements of fitness, and their evolution is usually explained in terms of sexual selection. This explanation remains unsatisfactory in some instances, for example, juvenile birds whose plumage is molted prior to adulthood and breeding. I first evaluate whether juvenile plumage reflectance signals dominance status in the Federally Threatened Florida scrub-jay (Aphelocoma coerulescens) using a combination of observational and experimental methods....
Show moreOrnamental traits are considered honest advertisements of fitness, and their evolution is usually explained in terms of sexual selection. This explanation remains unsatisfactory in some instances, for example, juvenile birds whose plumage is molted prior to adulthood and breeding. I first evaluate whether juvenile plumage reflectance signals dominance status in the Federally Threatened Florida scrub-jay (Aphelocoma coerulescens) using a combination of observational and experimental methods. Then I estimate the heritability, non-genetic maternal and environmental effects, and strength of selection on juvenile plumage reflectance using archived feather samples and a pedigree constructed from historical nest records. Finally, I compare plumage reflectance and its use as a signal between a wildland and suburban population of scrub-jays. I conclude that plumage reflectance is a signal of dominance, and that social selection can also drive the evolution of sexually dimorphic traits. In this species, plumage reflectance is heritable and influenced by maternal effects, but environmental effects are inconsequential. Although this trait appears to have an important function, only mean brightness and female hue are associated with lifetime reproductive success. Plumage reflectance was more UV-shifted in the suburban birds, but there is no reason to believe that urbanization decreases the value of this plumage as a signal. However, these plumage differences may facilitate dispersal from suburban areas, contributing to the decline of suburban populations.
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Date Issued: 2013
Identifier: CFE0005431, ucf:50413
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005431

Title: Integrating Differential Global Positioning Systems and Geographic Information Systems for Analysis and Mapping of Skeletal Dispersals.
Creator: Walter, Brittany, Schultz, John, Dupras, Tosha, Walker, John, University of Central Florida
Abstract / Description: Scene mapping is an integral part of processing a forensic scene with scattered human remains. By utilizing the appropriate mapping technique, investigators can accurately document the location of human remains and maintain a precise geospatial record of this evidence at a scene. Global positioning system (GPS) units have been used for years to survey the spatial distribution of large-scale archaeological sites. However, differential global positioning (DGPS) unit now provide decreased...
Show moreScene mapping is an integral part of processing a forensic scene with scattered human remains. By utilizing the appropriate mapping technique, investigators can accurately document the location of human remains and maintain a precise geospatial record of this evidence at a scene. Global positioning system (GPS) units have been used for years to survey the spatial distribution of large-scale archaeological sites. However, differential global positioning (DGPS) unit now provide decreased positional error suitable for small-scale surveys, such as forensic scenes. Because of the lack of knowledge concerning this utility in mapping a scene, controlled research is necessary to determine the practicality of using DGPS in mapping scattered human remains in different environments. The purpose of this research is to quantify the accuracy of a DGPS unit for mapping skeletal dispersals and to determine the applicability of this utility in mapping dispersed remains. First, the accuracy of the DGPS unit was determined using known survey markers in different environments. Secondly, several simulated scenes were constructed and mapped in open, tree-covered, and structure-obstructed environments using the DGPS. Factors considered included the extent of the dispersal, data collection time, and the use of offsets. Data were differentially postprocessed and compared in a geographic information system (GIS) to evaluate the most efficient recordation methods. Results of this study show that the DGPS is a viable option for mapping human remains in open areas. Furthermore, guidelines for accurate scene mapping using a DGPS unit will be provided, along with a discussion concerning the integration of DGPS into GIS for scene analysis and presentation.
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Date Issued: 2012
Identifier: CFE0004632, ucf:49919
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004632

Title: Variation in Prospecting Behavior and Drivers of Post-Fire Habitat Preference Among Juvenile Florida Scrub-Jays.
Creator: Sherer, David, Bohlen, Patrick, Bowman, Reed, Jenkins, David, University of Central Florida
Abstract / Description: Florida Scrub-Jays (Aphelocoma coerulescens, FLSJ; federally Threatened) are cooperatively breeding birds endemic to Florida and dependent on fire-maintained xeric oak scrub. FLSJs are year-round residents, highly territorial, and rarely disperse far from their natal territory. Lifetime reproductive success is highest among individuals breeding in early-successional habitat, usually less than 9 to 10 years post-fire. However, because scrub burns infrequently such early-successional, high...
Show moreFlorida Scrub-Jays (Aphelocoma coerulescens, FLSJ; federally Threatened) are cooperatively breeding birds endemic to Florida and dependent on fire-maintained xeric oak scrub. FLSJs are year-round residents, highly territorial, and rarely disperse far from their natal territory. Lifetime reproductive success is highest among individuals breeding in early-successional habitat, usually less than 9 to 10 years post-fire. However, because scrub burns infrequently such early-successional, high-quality habitat is extremely limited and competition for it as breeding space is likely intense. Because some birds live long enough to experience habitat succession, FLSJs also occupy later-successional overgrown scrub, even though both survival and fecundity decline. Although immigration rates into later-successional habitat decline, some birds settle there, perhaps to avoid competition. Prior to dispersal into new breeding territories, most non-breeders engage in pre-dispersal forays, which occur before and immediately after the breeding season. Because FLSJ territories occur across a gradient of post-fire succession, and young birds make frequent forays beyond their natal territories, and are highly visible while doing so, they are ideal models to test how individual and environmental factors drive habitat preference when exploring a post-fire mosaic. I investigated how individual behavioral phenotype, natal territory condition, and body condition relative to conspecifics influence extra-territorial foray behavior across a habitat mosaic that includes various time-since-fire (TSF) intervals. My study system was a population of individually marked FLSJs on 1,214-ha of managed scrub at Archbold Biological Station (Highlands County, Florida). I measured off-territory movements of 114 yearling birds in three annual cohorts and quantified habitat preference using fine-scale fire history records. These data, paired with behavioral assays and morphometric records for each individual FLSJ, allowed me to create and compare models of exploratory behavior underlying searching patterns during pre-breeding forays. My results indicate significant variation in habitat preference by individual FLSJs during forays, driven by an individual's behavioral phenotype and the TSF of its natal territory.
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Date Issued: 2019
Identifier: CFE0007864, ucf:52790
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007864

Title: Nonlinear Dynamics in Multimode Optical Fibers.
Creator: Eftekhar, Mohammad Amin, Christodoulides, Demetrios, Amezcua Correa, Rodrigo, Li, Guifang, Kaup, David, University of Central Florida
Abstract / Description: Multimode optical fibers have recently reemerged as a viable platform for addressing a number of long-standing issues associated with information bandwidth requirements and power-handling capabilities. The complex nature of heavily multimoded systems can be effectively exploited to observe altogether novel physical effects arising from spatiotemporal and intermodal linear and nonlinear processes. Here, we have studied nonlinear dynamics in multimode optical fibers (MMFs) in both the normal...
Show moreMultimode optical fibers have recently reemerged as a viable platform for addressing a number of long-standing issues associated with information bandwidth requirements and power-handling capabilities. The complex nature of heavily multimoded systems can be effectively exploited to observe altogether novel physical effects arising from spatiotemporal and intermodal linear and nonlinear processes. Here, we have studied nonlinear dynamics in multimode optical fibers (MMFs) in both the normal and anomalous dispersion regimes. In the anomalous dispersion regime, the nonlinearity leads to a formation of spatiotemporal 3-D solitons. Unlike in single-mode fibers, these solitons are not unique and their properties can be modified through the additional degrees of freedom offered by these multimoded settings. In addition, soliton related processes such as soliton fission and dispersive wave generation will be also drastically altered in such multimode systems. Our theoretical work unravels some of the complexities of the underlying dynamics and helps us better understand these effects. The nonlinear dynamics in such multimode systems can be accelerated through a judicious fiber design. A cancelation of Raman self-frequency shifts and Blue-shifting multimode solitons were observed in such settings as a result of an acceleration of intermodal oscillations. Spatiotemporal instabilities in parabolic-index multimode fibers will also be discussed. In the normal dispersion regime, this effect can be exploited to generate an ultrabroad and uniform supercontinuum that extends more than 2.5 octaves. To do so, the unstable spectral regions are pushed away from the pump, thus sweeping the entire spectrum. Multimode parabolic pulses were also predicted and observed in passive normally dispersive tapered MMFs. These setting can obviate the harsh bandwidth limitation present in single-mode system imposed by gain medium and be effectively used for realizing high power multimode fiber lasers. Finally, an instant and efficient second-harmonic generation was observed in the multimode optical fibers. Through a modification of initial conditions, the efficiency of this process could be enhanced to a record high of %6.5.
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Date Issued: 2018
Identifier: CFE0007399, ucf:52063
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007399

dispersal (4)	+ -
AERMOD (3)	+ -
Dispersion (3)	+ -
Dispersal (2)	+ -
Dispersion Modeling (2)	+ -

dispersion modeling (2)	+ -
3D display (1)	+ -
Accelerated Nonlinearities (1)	+ -
Air (1)	+ -
Air Quality (1)	+ -
Air quality (1)	+ -
Airport air quality (1)	+ -
Aphelocoma coerulescens (1)	+ -
Behavioral ecology (1)	+ -
Bragg Gratings (1)	+ -
Buffering Distance (1)	+ -
C & D (1)	+ -
C and D (1)	+ -
C&D landfill (1)	+ -
CAL3MSAT (1)	+ -
CAL3QHC (1)	+ -
CO (1)	+ -
Connectivity (1)	+ -
Construction and Demolition Landfills (1)	+ -
DGPS (1)	+ -
Delay Lines (1)	+ -
Dispersive Waves (1)	+ -
EDMS (1)	+ -
Feral pig (1)	+ -
Florida scrub-jay (1)	+ -

ETD Collection (21)	+ -
Honors Collection (2)	+ -

University of Central Florida (23)	+ -
Jenkins, David (5)	+ -
Bowman, Reed (2)	+ -
Cooper, Charles (2)	+ -
Dupras, Tosha (2)	+ -

Li, Guifang (2)	+ -
Randall, Andrew (2)	+ -
Schultz, John (2)	+ -
Wayson, Roger (2)	+ -
Alemadi, Shireen (1)	+ -
Amezcua Correa, Rodrigo (1)	+ -
Bernard, Alaina (1)	+ -
Bohlen, Patrick (1)	+ -
Bolyard, Steven (1)	+ -
Boughton, Elizabeth (1)	+ -
Brescacin, Camille (1)	+ -
Brown, Jeremiah (1)	+ -
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Christodoulides, Demetrios (1)	+ -
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Deng, Weiwei (1)	+ -
Eftekhar, Mohammad Amin (1)	+ -
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