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- Title
- PERIODIC NONLINEAR REFRACTIVE INDEX OF CARBON DISULFIDE VAPORS.
- Creator
-
Strunk, Evelyn, Hagan, David, University of Central Florida
- Abstract / Description
-
The purpose of this thesis is to explore the nonlinear refractive index of carbon disulfide vapors as opposed to its liquid form. With CS2 vapors, the vapors are less dense so they will rotate longer than liquid CS2 because there are less intermolecular interactions. The electric field of the beam causes the molecules to align with the electric field and applies a torque to the molecules. After this excitation, the molecules continue rotating. The rotations change the index of refraction of...
Show moreThe purpose of this thesis is to explore the nonlinear refractive index of carbon disulfide vapors as opposed to its liquid form. With CS2 vapors, the vapors are less dense so they will rotate longer than liquid CS2 because there are less intermolecular interactions. The electric field of the beam causes the molecules to align with the electric field and applies a torque to the molecules. After this excitation, the molecules continue rotating. The rotations change the index of refraction of the material. Continuous rotation of the molecules causes the index of refraction to be periodic which means the molecules are going through multiple revivals. I will analyze this periodic nonlinear index of refraction. However, some problems occurred while the experiment was being done as well as some issues of measuring CS2 because of white light continuum generation in the cell walls. To avoid these issues we measured the air in the lab and were able to observe the periodic change of index of refraction for O2 and N2 .
Show less - Date Issued
- 2014
- Identifier
- CFH0004619, ucf:45270
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004619
- Title
- Laser-induced crystallization mechanisms in chalcogenide glass materials for advanced optical functionality.
- Creator
-
Sisken, Laura, Richardson, Kathleen, Richardson, Martin, Shah, Lawrence, University of Central Florida
- Abstract / Description
-
Glass-ceramics (GC) are promising candidates for gradient refractive index (GRIN) optics. These multi-phase, composite materials also exhibit improved physical properties as compared to the parent base glass resulting from the formation of a secondary crystalline phase(s). Nanocrystal phase formation in a multi-component chalcogenide glass (ChG), (GeSe2-3As2Se3)(1-x)-(PbSe)x glass where x = 0-40 has been investigated, and the role of the starting material morphology has been correlated to the...
Show moreGlass-ceramics (GC) are promising candidates for gradient refractive index (GRIN) optics. These multi-phase, composite materials also exhibit improved physical properties as compared to the parent base glass resulting from the formation of a secondary crystalline phase(s). Nanocrystal phase formation in a multi-component chalcogenide glass (ChG), (GeSe2-3As2Se3)(1-x)-(PbSe)x glass where x = 0-40 has been investigated, and the role of the starting material morphology has been correlated to the resulting composite's optical properties including refractive index, transmission, dispersion, and thermo-optic coefficient. Optical property evolution was related to the type and amount of the crystal phases formed, since through control of the local volume fraction of crystalline phase(s), the effective material properties of the composite can locally be varied. Through computational and experimental studies, tailored nanocomposites exhibiting gradient index properties have been realized. A Raman spectroscopic technique was developed as a means to spatially quantify the extent of conversion from glass to glass ceramic, and to confirm that the scale length of the local refractive index modification can be correlated to the extent of crystallization as validated by X-ray diffraction (XRD). Spatial control of the crystallization was examined by using a laser to locally modify the amount of nucleation and/or growth of crystallites in the glass. A novel technique converse to laser-induced crystallization was also developed and demonstrated that a glass ceramic could be locally re-vitrified back to a fully glassy state, through a laser-induced vitrification (LIV) method. Proof-of-concept demonstrator optics were developed using furnace and laser induced crystallization methods to validate experimental and computational approaches to modify the local volume fraction of nano-crystals. These demonstrators exhibited tailorable optical functionality as focusing optics and diffractive optics. This work paves the way for the design and fabrication of nanocomposite GRIN optics and their use in the mid-wave infrared.
Show less - Date Issued
- 2017
- Identifier
- CFE0006916, ucf:51684
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006916
- Title
- MODELING AND CHARACTERIZATION OF ACUTE STRESS UNDER DYNAMIC TASK CONDITIONS.
- Creator
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Millan, Angel, Crumpton-Young, Lesia, University of Central Florida
- Abstract / Description
-
Stress can be defined as the mental, physical, and emotional response of humans to stressors encountered in their personal or professional environment. Stressors are introduced in various activities, especially those found in dynamic task conditions when multiple task requirements must be performed. Stress and stressors have been described as activators and inhibitors of human performance. The ability to manage high levels of acute stress is an important determinant of successful performance...
Show moreStress can be defined as the mental, physical, and emotional response of humans to stressors encountered in their personal or professional environment. Stressors are introduced in various activities, especially those found in dynamic task conditions when multiple task requirements must be performed. Stress and stressors have been described as activators and inhibitors of human performance. The ability to manage high levels of acute stress is an important determinant of successful performance in any occupation. In situations where performance is critical, personnel must be prepared to operate successfully under hostile or extreme stress conditions; therefore training programs and engineered systems must be tailored to assist humans in fulfilling these demands. To effectively design appropriate training programs for these conditions, it is necessary to quantitatively describe stress. A series of theoretical stress models have been developed in previous research studies; however, these do not provide quantification of stress levels nor the impact on human performance. By modeling acute stress under dynamic task conditions, quantitative values for stress and its impact on performance can be assessed. Thus, this research was designed to develop a predictive model for acute stress as a function of human performance and task demand. Initially, a four factor two level experimental design [2 (Noise) x 2 (Temperature) x 2 (Time Awareness) x 2 (Workload)] was performed to identify reliable physiological, cognitive and behavioral responses to stress. Next, multivariate analysis of variance (n=108) tests were performed, which showed statistically significant differences for physiological, cognitive and behavioral responses. Finally, fuzzy set theory techniques were used to develop a comprehensive stress index model. Thus, the resulting stress index model was constructed using input on physiological, cognitive and behavioral responses to stressors as well as characteristics inherent to the type of task performed and personal factors that interact as mediators (competitiveness, motivation, coping technique and proneness to boredom). Through using this stress index model to quantify and characterize the affects of acute stress on human performance, these research findings can inform proper training protocols and help to redesign tasks and working conditions that are prone to create levels of acute stress that adversely affect human performance.
Show less - Date Issued
- 2011
- Identifier
- CFE0004056, ucf:49151
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004056
- Title
- AUTONOMOUS REPAIR OF OPTICAL CHARACTER RECOGNITION DATA THROUGH SIMPLE VOTING AND MULTI-DIMENSIONAL INDEXING TECHNIQUES.
- Creator
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Sprague, Christopher, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
The three major optical character recognition (OCR) engines (ExperVision, Scansoft OCR, and Abby OCR) in use today are all capable of recognizing text at near perfect percentages. The remaining errors however have proven very difficult to identify within a single engine. Recent research has shown that a comparison between the errors of the three engines proved to have very little correlation, and thus, when used in conjunction, may be useful to increase accuracy of the final result. This...
Show moreThe three major optical character recognition (OCR) engines (ExperVision, Scansoft OCR, and Abby OCR) in use today are all capable of recognizing text at near perfect percentages. The remaining errors however have proven very difficult to identify within a single engine. Recent research has shown that a comparison between the errors of the three engines proved to have very little correlation, and thus, when used in conjunction, may be useful to increase accuracy of the final result. This document discusses the implementation and results of a simple voting system designed to prove the hypothesis and show a statistical improvement in overall accuracy. Additional aspects of implementing an improved OCR scheme such as dealing with multiple engine data output alignment and recognizing application specific solutions are also addressed in this research. Although voting systems are currently in use by many major OCR engine developers, this research focuses on the addition of a collaborative system which is able to utilize the various positive aspects of multiple engines while also addressing the immediate need for practical industry applications such as litigation and forms processing. Doculex TM, a major developer and leader in the document imaging industry, has provided the funding for this research.
Show less - Date Issued
- 2005
- Identifier
- CFE0000380, ucf:46337
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000380
- Title
- BENCHMARK STUDIES FOR STRUCTURAL HEALTH MONITORING USING ANALYTICAL AND EXPERIMENTAL MODELS.
- Creator
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Burkett, Jason, Catbas, Necati, University of Central Florida
- Abstract / Description
-
The latest bridge inventory report for the United States indicates that 25% of the highway bridges are structurally deficient or functionally obsolete. With such a large number of bridges in this condition, safety and serviceability concerns become increasingly relevant along with the associated increase in user costs and delays. Biennial inspections have proven subjective and need to be coupled with standardized non-destructive testing methods to accurately assess a bridge's condition for...
Show moreThe latest bridge inventory report for the United States indicates that 25% of the highway bridges are structurally deficient or functionally obsolete. With such a large number of bridges in this condition, safety and serviceability concerns become increasingly relevant along with the associated increase in user costs and delays. Biennial inspections have proven subjective and need to be coupled with standardized non-destructive testing methods to accurately assess a bridge's condition for decision making purposes. Structural health monitoring is typically used to track and evaluate performance, symptoms of operational incidents, anomalies due to deterioration and damage during regular operation as well as after an extreme event. Dynamic testing and analysis are concepts widely used for health monitoring of existing structures. Successful health monitoring applications on real structures can be achieved by integrating experimental, analytical and information technologies on real life, operating structures. Real-life investigations must be backed up by laboratory benchmark studies. In addition, laboratory benchmark studies are critical for validating theory, concepts, and new technologies as well as creating a collaborative environment between different researchers. To implement structural health monitoring methods and technologies, a physical bridge model was developed in the UCF structures laboratory as part of this thesis research. In this study, the development and testing of the bridge model are discussed after a literature review of physical models. Different aspects of model development, with respect to the physical bridge model are outlined in terms of design considerations, instrumentation, finite element modeling, and simulating damage scenarios. Examples of promising damage detection methods were evaluated for common damage scenarios simulated on the numerical and physical models. These promising damage indices were applied and directly compared for the same experimental and numerical tests. To assess the simulated damage, indices such as modal flexibility and curvature were applied using mechanics and structural dynamics theory. Damage indices based on modal flexibility were observed to be promising as one of the primary indicators of damage that can be monitored over the service life of a structure. Finally, this thesis study will serve an international effort that has been initiated to explore bridge health monitoring methodologies under the auspices of International Association for Bridge Maintenance and Safety (IABMAS). The data generated in this thesis research will be made available to researchers as well as practitioners in the broad field of structural health monitoring through several national and international societies, associations and committees such as American Society of Civil Engineers (ASCE) Dynamics Committee, and the newly formed ASCE Structural Health Monitoring and Control Committee.
Show less - Date Issued
- 2005
- Identifier
- CFE0000636, ucf:46514
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000636
- Title
- OWNERSHIP DIVERSITY WITHIN THE MEDIA INDUSTRY: TRENDS AND CURRENT CONDITIONS.
- Creator
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Vizcarrondo, Thomas E, Costain, Gene, University of Central Florida
- Abstract / Description
-
This study seeks to determine if media ownership diversity remains at levels widely considered to be competitive and acceptable, despite consolidation within the media industry. The research augments the many studies analyzing programming diversity within the U. S. media industry. Rather than analyzing programming content, this study addresses ownership diversity by examining the diversity of media ownership within the context U. S. model, considered to be more of a decentralized, market...
Show moreThis study seeks to determine if media ownership diversity remains at levels widely considered to be competitive and acceptable, despite consolidation within the media industry. The research augments the many studies analyzing programming diversity within the U. S. media industry. Rather than analyzing programming content, this study addresses ownership diversity by examining the diversity of media ownership within the context U. S. model, considered to be more of a decentralized, market-driven media industry when compared to other countries such as the United Kingdom or Canada. To measure diversity, the Herfindahl-Hirschman Index (HHI)--a measure of economic diversity widely used by economists as well as government regulatory agencies--is used. Suggestions are presented for the future of media and regulation to insure a competitive, diverse, and healthy media industry.
Show less - Date Issued
- 2004
- Identifier
- CFE0000122, ucf:46189
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000122
- Title
- THE SYNERGIES BETWEEN TOURISM EXPANSION AND DEVELOPMENT: AN ANALYSIS OF ECONOMIC GROWTH, POVERTY AND HUMAN DEVELOPMENT IN ECUADOR.
- Creator
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Rivera, Manuel, Croes, Robertico, Hara, Tadayuki, Pizam, Abraham, Robinson, Edward, Maunez-Cuadra, Jose, University of Central Florida
- Abstract / Description
-
ABSTRACTThis dissertation attempts to answer the question of what has been the effect of tourism expansion and development in Ecuador. We attempt to analyze, both theoretically and empirically, the relationship between tourism and development. There have been an enormous number of studies explaining how tourism can affect the various dimensions of development. However, no research has been undertaken to simultaneously empirically examine the impact that changes in tourism expansion has on...
Show moreABSTRACTThis dissertation attempts to answer the question of what has been the effect of tourism expansion and development in Ecuador. We attempt to analyze, both theoretically and empirically, the relationship between tourism and development. There have been an enormous number of studies explaining how tourism can affect the various dimensions of development. However, no research has been undertaken to simultaneously empirically examine the impact that changes in tourism expansion has on poverty, human development, and economic growth.To this end, we propose a cointergation methodology with an error correction model to estimate the impact of tourism expansion on poverty, human development, and economic growth. This study employs time series data from 1988 to 2008 as well as a Granger causality test to examine the hypothesized relationships. The five most important results are, first, that tourism seems to have distinguishable effects on reducing poverty. In the case of Ecuador, a tourism poverty nexus exists and it helps fight poverty in terms of intensity, inequality, and the proportion of poor. Secondly, economic growth is Ecuador is (")pro-poor("). Increases in economic growth have both short and long term effects on poverty reduction. Thirdly, tourism does not yet promotes human development but the other way around. Therefore a virtuous cycle between tourism and human development does not exist yet. Therefore, opportunities exist to further promote tourism in an attempt to support human development programs. Fourthly, economic growth promotes human development but human development does not yet promotes growth. These results suggest that Ecuador is in HD lopsided situation when it comes to economic growth and human development. Finally, the relationship between tourism and economic growth is bi-directional; the expansion of either sector promotes the growth of the other.
Show less - Date Issued
- 2011
- Identifier
- CFE0004161, ucf:49052
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004161
- Title
- PHONEME-BASED VIDEO INDEXING USING PHONETIC DISPARITY SEARCH.
- Creator
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Leon-Barth, Carlos, DeMara, Ronald, University of Central Florida
- Abstract / Description
-
This dissertation presents and evaluates a method to the video indexing problem by investigating a categorization method that transcribes audio content through Automatic Speech Recognition (ASR) combined with Dynamic Contextualization (DC), Phonetic Disparity Search (PDS) and Metaphone indexation. The suggested approach applies genome pattern matching algorithms with computational summarization to build a database infrastructure that provides an indexed summary of the original audio content....
Show moreThis dissertation presents and evaluates a method to the video indexing problem by investigating a categorization method that transcribes audio content through Automatic Speech Recognition (ASR) combined with Dynamic Contextualization (DC), Phonetic Disparity Search (PDS) and Metaphone indexation. The suggested approach applies genome pattern matching algorithms with computational summarization to build a database infrastructure that provides an indexed summary of the original audio content. PDS complements the contextual phoneme indexing approach by optimizing topic seek performance and accuracy in large video content structures. A prototype was established to translate news broadcast video into text and phonemes automatically by using ASR utterance conversions. Each phonetic utterance extraction was then categorized, converted to Metaphones, and stored in a repository with contextual topical information attached and indexed for posterior search analysis. Following the original design strategy, a custom parallel interface was built to measure the capabilities of dissimilar phonetic queries and provide an interface for result analysis. The postulated solution provides evidence of a superior topic matching when compared to traditional word and phoneme search methods. Experimental results demonstrate that PDS can be 3.7% better than the same phoneme query, Metaphone search proved to be 154.6% better than the same phoneme seek and 68.1 % better than the equivalent word search.
Show less - Date Issued
- 2010
- Identifier
- CFE0003480, ucf:48979
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003480
- Title
- A NEW DEVELOPMENT OF FEEDBACK CONTROLLER FOR LEFT VENTRICULAR ASSIST DEVICE.
- Creator
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Wang, Yu, Simaan, Marwan, University of Central Florida
- Abstract / Description
-
The rotary Left Ventricular Assist Device (LVAD) is a mechanical pump surgically implanted in patients with end-stage congestive heart failure to help maintain the flow of blood from the sick heart. The rotary type pumps are controlled by varying the impeller speed to control the amount of blood flowing through the LVAD. One important challenge in using these devices is to prevent the occurrence of excessive pumping of blood from the left ventricle (known as suction) that may cause it to...
Show moreThe rotary Left Ventricular Assist Device (LVAD) is a mechanical pump surgically implanted in patients with end-stage congestive heart failure to help maintain the flow of blood from the sick heart. The rotary type pumps are controlled by varying the impeller speed to control the amount of blood flowing through the LVAD. One important challenge in using these devices is to prevent the occurrence of excessive pumping of blood from the left ventricle (known as suction) that may cause it to collapse due to the high pump speed. The development of a proper feedback controller for the pump speed is therefore crucial to meet this challenge. In this thesis, some theoretical and practical issues related to the development of such a controller are discussed. First, a basic nonlinear, time-varying cardiovascular-LVAD circuit model that will be used to develop the controller is reviewed. Using this model, a suction index is tested to detect suction. Finally we propose a feedback controller that uses the pump flow signal to regulate the pump speed based on the suction index and an associated threshold. The objective of this controller is to continuously update the pump speed to adapt to the physiological changes of the patient while at the same time avoiding suction. Simulation results are presented under different conditions of the patient activities. Robustness of the controller to measurement noise is also discussed.
Show less - Date Issued
- 2010
- Identifier
- CFE0003296, ucf:48497
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003296
- Title
- Nutrition Literacy and Demographic Variables as Predictors of Adolescent Weight Status in a Florida County.
- Creator
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Damato-Kubiet, Leslee, Sole, Mary, Bushy, Angeline, Conner, Norma, Berman, Steven, University of Central Florida
- Abstract / Description
-
Problem: In recent years, childhood obesity has increased to epidemic proportions across the United States (U.S.) in parallel with adult obesity, which often reflects poor dietary choices and bad nutritional habits. Purpose: The primary purpose of this study was to examine the effects of parent and adolescent nutrition literacy expressed as nutrition knowledge and skills, with total household income and parent level of education, as predictors of weight status in adolescents that live in a...
Show moreProblem: In recent years, childhood obesity has increased to epidemic proportions across the United States (U.S.) in parallel with adult obesity, which often reflects poor dietary choices and bad nutritional habits. Purpose: The primary purpose of this study was to examine the effects of parent and adolescent nutrition literacy expressed as nutrition knowledge and skills, with total household income and parent level of education, as predictors of weight status in adolescents that live in a Florida community. The secondary purpose of this study was to examine the implications for nutrition literacy levels within parent/adolescent dyads to identify public health initiatives aimed at adult and adolescent populations.Methods: A descriptive, correlational design was used to collect data from a convenience sample of 110 parent-adolescent dyads recruited from a free physical exam event hosted by a local health care facility. Three instruments were completed by each dyad: 1) demographic survey, 2) Nutrition Literacy Survey (NLS; knowledge), and 3) Newest Vital Sign (NVS; skills). Physiologic measurements for the study included anthropometric measurement of the adolescent child's height (cm) and weight (kg) without shoes and BMI scores were calculated. In addition to actual value, BMI was categorized as low/normal and overweight/obese for analysis. Paired t-tests were used to compare means for the NLS and NVS survey in parent-adolescent dyads. Bivariate correlation scores were computed between the two variables of parent/adolescent NLS and NVS scores. Lastly, regression models for examining adolescent BMI were compared with the independent variables of the study.Results: The sample of adult participants (n =110) comprised males (n = 30, 27%) and females (n =80, 73%) ranging in age from 34 to 55 years (M= 41.9, SD= 4.77). Adolescent participants (n=110) comprised males (n = 61, 55%) and females (n = 49, 45%) ranging in age from 13 to 17 years (M = 15.1, SD = 1.43). Adolescent male participants had higher BMI (27 + 3.48) than females (24 + 2.90), t (108) = 4.83, (p = (<) .001). Adolescent males were categorized more overweight/obese than females (67.2% versus 24.5%). The parent NLS mean score (M=19) indicated low overall levels of general nutrition knowledge whereas the adolescent NLS mean score (M=21.7) demonstrated greater aptitude for nutrition knowledge than parent scores. The parent NVS mean score (M=4.1) suggested adequate levels of nutrition skills. Likewise, the adolescent NVS mean score (M= 4.1) suggested adequate nutrition skills, similar to scores in the adult population. Spearman rho correlations yielded positive correlations between parent/adolescent nutrition knowledge, (rs = .224, p = .019), and parents' nutrition knowledge and skills (rs = .596, p (<) .001). Positive correlations were also noted between adolescents' nutrition knowledge and parents' nutrition skills (rs = .257, p = .007) and adolescents' nutrition knowledge and nutrition skills (rs = .260. p = .006). Three regression models were calculated to examine adolescent BMI with the independent variables of the study. Analysis of regression coefficients for each model indicated that none of the variables demonstrated significance as a predictor of adolescent BMI.Discussion/Implications: The results of the study suggest that parents and adolescents may have similar amounts of nutrition literacy when examining the constructs of nutrition knowledge and skills; however, BMI is not solely dependent on these skill sets. Examination of the factors that influence parents and adolescent children's weight status are important elements in shaping families adoption of sound dietary habits and improving health outcomes.
Show less - Date Issued
- 2013
- Identifier
- CFE0005154, ucf:50685
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005154
- Title
- A FLUID STRUCTURE INTERACTION MODEL OF INTRACORONARY ATHEROSCLEROTIC PLAQUE RUPTURE.
- Creator
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TEUMA-MELAGO, Eric, Ilegbusi, Olusegun, University of Central Florida
- Abstract / Description
-
Plaque rupture with superimposed thrombosis is the primary cause of acute coronary syndromes of unstable angina, myocardial infarction and sudden death. Although intensive studies in the past decade have shed light on the mechanism that causes unstable atheroma, none has directly addressed the clinical observation that most myocardial infarction (MI) patients have moderate stenoses (less than 50%). Considering the important role the arterial wall compliance and pulsitile blood flow play in...
Show morePlaque rupture with superimposed thrombosis is the primary cause of acute coronary syndromes of unstable angina, myocardial infarction and sudden death. Although intensive studies in the past decade have shed light on the mechanism that causes unstable atheroma, none has directly addressed the clinical observation that most myocardial infarction (MI) patients have moderate stenoses (less than 50%). Considering the important role the arterial wall compliance and pulsitile blood flow play in atheroma rupture, fluid-structure interaction (FSI) phenomenon has been of interest in recent studies. In this thesis, the impact is investigated numerically of coupled blood flow and structural dynamics on coronary plaque rupture. The objective is to determine a unique index that can be used to characterize plaque rupture potential. The FSI index, developed in this study for the first time derives from the theory of buckling of thin-walled cylinder subjected to radial pressure. Several FSI indices are first defined by normalizing the predicted hemodynamic endothelial shear stress by the structural stresses, specifically, by the maximum principal stress (giving the ratio ), and the Von Mises stress (giving the ratio ). The predicted at the location of maximum (i.e { }) denoted , is then chosen to characterize plaque rupture through systematic investigation of a variety of plaque characteristics and simulated patient conditions. The conditions investigated include varying stenosis levels ranging from 20% to 70%, blood pressure drop ranging from 3125 Pa/m to 9375 Pa/m, fibrous cap thickness ranging from to , lipid pool location ranging from the leading to the trailing edge of plaque, lipid pool volume relative to stenosis volume ranging from 24% to 80%, Calcium volume relative to stenosis volume ranging from 24% to 80% and arterial remodeling. The predicted varies with the stenosis severity and indicates that the plaques investigated are prone to rupture at approximately 40-45% stenosis levels. It predicts that high pressure significantly lowers the threshold stenosis rate for plaque rupture. In addition, the plaque potential to rupture increases for relatively thin fibrous cap, lipid core located near the leading plaque shoulder, and dramatically for relative lipid pool volume above 60%. However, calcium deposit has marginal effect on plaque rupture. Overall, the predicted results are consistent with clinical observations, indicating that the has the potential to characterize plaque rupture when properly established. In the appendix, the unsteady flow in a collapsible tube model of a diseased artery is solved analytically. The novelty of our approach is that the set of governing equations is reduced to a single integro-differential equation in the transient state. The equation was solved using the finite difference method to obtain the pressure and compliant wall behavior. The analytical approach is less computer-intensive than solving the full set of governing equations. The predicted membrane deflection is quite large at low inlet velocity, suggesting possible approach to breakdown in equilibrium. As the transmural pressure increases with wall deflection, bulges appear at the ends of the membrane indicating critical stage of stability, consistent with previous studies. An increase in wall thickness reduces the wall deflection and ultimately results in its collapse. The collapse is due to breakdown in the balance of wall governing equation. An increase in internal pressure is required to maintain membrane stability.
Show less - Date Issued
- 2006
- Identifier
- CFE0001471, ucf:47084
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001471
- Title
- JUVENILE GREEN TURTLE (CHELONIA MYDAS) FORAGING ECOLOGY:FEEDING SELECTIVITY AND FORAGE NUTRIENT ANALYSIS.
- Creator
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Gilbert, Eliza, Ehrhart, Llewellyn, University of Central Florida
- Abstract / Description
-
For the endangered green turtle, Chelonia mydas, a fundamental component of recovery and conservation is an understanding of its foraging ecology. Foraging optimality models suggest animals will select resources of high quality over those of low quality. For green turtles, this behavior is important, as sufficient quantities of nutritionally adequate forage items are necessary for growth and reproduction. One intrinsic element in the understanding of green turtle foraging ecology is to...
Show moreFor the endangered green turtle, Chelonia mydas, a fundamental component of recovery and conservation is an understanding of its foraging ecology. Foraging optimality models suggest animals will select resources of high quality over those of low quality. For green turtles, this behavior is important, as sufficient quantities of nutritionally adequate forage items are necessary for growth and reproduction. One intrinsic element in the understanding of green turtle foraging ecology is to identify and document the availability and quality of forage resources preferred by green turtles. The objectives of this study were: 1) determine whether juvenile green turtles showed a feeding preference by comparing prey items in the diet to the availability of those items in the habitat, 2) identify species for which there was selection or avoidance, 3) identify nutritional factors determining selection or avoidance of prey items, and 4) evaluate the nutritional content of the diet. This research was conducted by comparing lavage samples from juvenile green turtles to samples from benthic surveys within the habitat. To determine feeding preference, Ivlev's Electivity Index was used to compare ingested species of algae with those available in the habitat. Nutritional analysis of forage was conducted to identify possible nutrients relating to feeding preference. Juvenile green turtles selectively foraged on Chlorophyta and Rhodophyta. Results indicate that diet selection was based on nutritional content. Both the composite diet and the main diet item, Hypnea spp, had a higher gross energy value, were higher in protein, and lower in fiber than prey items that were avoided. Conservation of green turtles requires effective habitat management, which must be informed by an understanding and evaluation of the habitat. For juvenile green turtles, this study indicates that habitats dominated by Chlorophyta and Rhodophyta may be more important for the health of green turtle populations than habitats dominated by Phaeophyta.
Show less - Date Issued
- 2005
- Identifier
- CFE0000487, ucf:46355
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000487
- Title
- SCALABLE VOLUMETRIC THREE-DIMENSIONAL UP-CONVERSION DISPLAY MEDIUM.
- Creator
-
Cho, Jung-Hyun, Bass, Michael, University of Central Florida
- Abstract / Description
-
There are many different techniques to display 3D information. However, not many of them are able to provide sufficient depth cues to the observers to sense or feel the images as real three-dimensional objects. Volumetric three-dimensional displays generate images within a real 3D space, so they provide most of the depth cues automatically. This thesis discusses the basic notions required to understand three-dimensional displays. Also discussed are different techniques used to display 3D...
Show moreThere are many different techniques to display 3D information. However, not many of them are able to provide sufficient depth cues to the observers to sense or feel the images as real three-dimensional objects. Volumetric three-dimensional displays generate images within a real 3D space, so they provide most of the depth cues automatically. This thesis discusses the basic notions required to understand three-dimensional displays. Also discussed are different techniques used to display 3D information and their advantages and disadvantages as well as their current limitations. Several rare-earth doped fluoride crystals that are excited to emit visible light by sequential two photon absorption have been investigated as display medium candidates for static volumetric three dimensional displays. A scalable display medium is suggested to enable large 3D displays. This medium is a dispersion of particles of the rare earth doped fluoride crystals in a refractive index-matched polymer matrix. Detailed experiments are described to prepare such a scalable display medium using a wide variety of polymers. The scattering problem in such a medium was greatly reduced by index-matching the polymer to the crystalline particles. An index-matching condition that optimizes the performance was identified and demonstrated. A potential near-future solution is demonstrated and improvements are suggested.
Show less - Date Issued
- 2007
- Identifier
- CFE0001899, ucf:47405
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001899
- Title
- THE ROLE OF STRESS IN THE DIFFERENTIAL DIAGNOSIS OF APRAXIA OF SPEECH AND APHASIA.
- Creator
-
Ferranti, Jennifer G, Troche, Joshua, Bislick-Wilson, Lauren, University of Central Florida
- Abstract / Description
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The intent of this thesis is to explore and develop the quantification of AOS features, particularly the deficits of prosodic elements, lexical stress and duration. This study investigated whether PVI can be used as a sensitive tool for the differential diagnosis of AOS. Specifically, we sought to determine whether analysis of vowel length of stressed and unstressed syllables is helpful in differentiating between individuals with AOS and aphasia versus aphasia alone. Significant differences...
Show moreThe intent of this thesis is to explore and develop the quantification of AOS features, particularly the deficits of prosodic elements, lexical stress and duration. This study investigated whether PVI can be used as a sensitive tool for the differential diagnosis of AOS. Specifically, we sought to determine whether analysis of vowel length of stressed and unstressed syllables is helpful in differentiating between individuals with AOS and aphasia versus aphasia alone. Significant differences support the hypothesis that PVI, analyzed from vowel length, is uniquely affected in AOS. This yields reason for further research in prosodic deficits in differential diagnosis, as well as application of this theory for a speech-language pathologist.
Show less - Date Issued
- 2018
- Identifier
- CFH2000388, ucf:45746
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000388
- Title
- THE EFFECTS OF DEVELOPMENT ON POLICIES IN THE PREVENTION OF INTERNATIONAL HUMAN TRAFFICKING.
- Creator
-
Szczerba, Christopher, Sadri, Houman, University of Central Florida
- Abstract / Description
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Governments and leaders across the globe almost universally agree that human trafficking is a modern atrocity that has harshly negative effects for individuals, communities, entire states and the international community. Nevertheless, they are not in agreement on how best to investigate cases and provide aid to victims. Many states lack the resources to effectively create and implement policies. Governments must act to protect their citizens and people within their borders. Policies are...
Show moreGovernments and leaders across the globe almost universally agree that human trafficking is a modern atrocity that has harshly negative effects for individuals, communities, entire states and the international community. Nevertheless, they are not in agreement on how best to investigate cases and provide aid to victims. Many states lack the resources to effectively create and implement policies. Governments must act to protect their citizens and people within their borders. Policies are necessary to correctly identify victims, investigate accusations, bring cases to trial and prevent vulnerable populations from becoming victimized through awareness. This thesis asserts that there is a link between the development level of a state and its ability to limit the grotesque crimes of trafficking that occur within its borders. Using the United Nation's annual report which details the development ranking of individual states, it is possible to comparatively analyze the ability of these states to comply with international standards established by the United States of America in the protection of victims of human trafficking. Special attention is paid to the challenges that societies face when there are drastic changes to states' economic activity or political stability and how these affect the frequency of trafficking occurrences and a government's ability to respond.
Show less - Date Issued
- 2014
- Identifier
- CFH0004579, ucf:45158
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004579
- Title
- TRACKING ERROR OF LEVERAGED AND INVERSE ETFS.
- Creator
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Romano, John, Gilkeson, Jim, University of Central Florida
- Abstract / Description
-
Tracking ability of leveraged and inverse exchange traded funds can be very important to investors looking for a dependable return. If the investor wants to put their money on a certain index they feel strongly about, they expect their investment vehicle to track that return appropriately. Over the years, we have seen tremendous growth in the exchange traded fund industry. In 2006, leveraged and inverse funds were introduced to the market, allowing investors to take leveraged and directional...
Show moreTracking ability of leveraged and inverse exchange traded funds can be very important to investors looking for a dependable return. If the investor wants to put their money on a certain index they feel strongly about, they expect their investment vehicle to track that return appropriately. Over the years, we have seen tremendous growth in the exchange traded fund industry. In 2006, leveraged and inverse funds were introduced to the market, allowing investors to take leveraged and directional trades on indices. These investment vehicles can be traded as easily as any stock, and therefore need some attention. Since any novice investor can access and trade these funds, they need to be aware of the risks they are taking. In this study, I test whether the ProShares S&P tracking leveraged and inverse exchange traded funds track their appropriate index multiple as promised. I did this by running regressions on each fund against the appropriate multiple of their underlying indices. I did this for funds of different market capitalization, for different holding periods, and with different amounts of leverage, to compare how these funds track in different conditions. I found that the large cap funds tend to track the best, with the small cap funds tracking the worst. I also find that tracking error tends to increase with longer holding periods. I find that the distribution of excess returns becomes less normal over longer holding periods, and begins to flatten out and widen. There does not seem to be a concrete conclusion as to whether or not the amount of leverage affects the tracking ability of the funds. I end up with mixed results when comparing amounts of leverage by model fit and by tracking error. Direction also does not seem to play any role in the tracking ability of these funds.
Show less - Date Issued
- 2012
- Identifier
- CFH0004184, ucf:44893
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004184
- Title
- Color-Ratio Based Strawberry Plant Localization and Nutrition Deficiency Detection.
- Creator
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Kong, Xiangling, Xu, Yunjun, Elgohary, Tarek, Fu, Qiushi, Wu, Dazhong, Wang, Liqiang, University of Central Florida
- Abstract / Description
-
In recent years, precision agriculture has become popular anticipating to partially meet the needs of an ever-growing population with limited resources. Plant localization and nutrient de?ciency detection are two important tasks in precision agriculture. In this dissertation, these two tasks are studied by using a new color-ratio(C-R) index technique. Firstly, a low cost and light scene invariant approach is proposed to detect green and yellow leaves based on the color-ratio (C-R) indices. A...
Show moreIn recent years, precision agriculture has become popular anticipating to partially meet the needs of an ever-growing population with limited resources. Plant localization and nutrient de?ciency detection are two important tasks in precision agriculture. In this dissertation, these two tasks are studied by using a new color-ratio(C-R) index technique. Firstly, a low cost and light scene invariant approach is proposed to detect green and yellow leaves based on the color-ratio (C-R) indices. A plant localization approach is then developed using the relative pixel relationships of adjacent plants. Secondly, the Sobel operator and morphology techniques are applied to segment the target strawberry leaf from a ?eld image. The characterized color for a speci?c nutrient de?ciency is detected by the C-R indices. The pattern of the detected color on the leaf is then examined to determine the speci?c nutrient de?ciency. The proposed approaches are validated in a commercial strawberry farm.
Show less - Date Issued
- 2019
- Identifier
- CFE0007666, ucf:52482
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007666
- Title
- Modeling the innovation ecosystem and development of a dynamic innovation index.
- Creator
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Schoen, Henriette, Karwowski, Waldemar, Hoekstra, Robert, Shumaker, Randall, Akbas, Mustafa, University of Central Florida
- Abstract / Description
-
The topic of innovation currently generates a tremendous amount of interest around the world. Innovation is considered an essential part of the solution to creating more jobs and improving the socio-economic conditions of many countries around the globe. Innovation comes about through the existence of many interrelated solutions to socio-economic problems in an extensively interconnected network, which create value for each other. Such a complex creativity and innovation value-creating...
Show moreThe topic of innovation currently generates a tremendous amount of interest around the world. Innovation is considered an essential part of the solution to creating more jobs and improving the socio-economic conditions of many countries around the globe. Innovation comes about through the existence of many interrelated solutions to socio-economic problems in an extensively interconnected network, which create value for each other. Such a complex creativity and innovation value-creating network is here called an Innovation Ecosystem (IE). The main objective of this dissertation research is to improve the current understanding of the IE by developing a simulation model that uses a broad set of relevant static and dynamic variables and incorporates the principles of system dynamics (SD). The proposed model, which is named the IECO-model is based on the relationships between 91 variables and the combined influences of the 43 parameters. Available data for 32 countries, representing a full span of GDP worldwide, was used to study the level of innovation in each of these countries. The result of the developed IECO-model is a novel ranking of the level of innovation through a dynamic innovation index, called the DII. The DII is a new tool to evaluate the innovation and entrepreneurship level of a given country in the context of the global economy. The most significant differentiator from other existing indices of innovation is that the DII is focusing more on the entrepreneurship qualities in 19 of the 43 parameters by looking at cultural values and belief systems, the social context, existing entrepreneurial culture, innovation attitudes, and mentality of each of the considered countries. According to DII-based ranking, the ten most innovative countries in the world are 1. Switzerland, 2. USA, 3. Finland, 4. Netherlands, 5. Iceland, 6. Sweden, 7. Germany, 8. Denmark, 9. The United Kingdom, and 10. Austria.
Show less - Date Issued
- 2018
- Identifier
- CFE0007586, ucf:52537
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007586
- Title
- INTEGRATING THEORY, PRACTICE AND POLICY: THE TECHNICAL EFFICIENCY AND PRODUCTIVITY OF FLORIDA'S CIRCUIT COURTS.
- Creator
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Ferrandino, Joseph, Wan, Thomas T.H., University of Central Florida
- Abstract / Description
-
In 1998, Florida voters approved Article V, Revision 7, which changed the funding mechanism of the state circuit court system from a county/state mix to state responsibility. The change was implemented as planned in the 2004/05 fiscal year. Although increased efficiency was a key goal of Revision 7, to date no published studies exist on the impacts of Revision 7 on circuit or system efficiency and/or productivity. This work analyzes Revision 7, integrating the larger debate of increasing...
Show moreIn 1998, Florida voters approved Article V, Revision 7, which changed the funding mechanism of the state circuit court system from a county/state mix to state responsibility. The change was implemented as planned in the 2004/05 fiscal year. Although increased efficiency was a key goal of Revision 7, to date no published studies exist on the impacts of Revision 7 on circuit or system efficiency and/or productivity. This work analyzes Revision 7, integrating the larger debate of increasing judgeships or improving efficiency.The study is a full performance analysis of the Florida circuit courts from 1993 through 2008 that can benchmark the system's future efficiency and productivity. In that respect, top performers are identified. The study follows the evolution of court studies from their rational origins to the more recent orientation of open-natural systems. Resource dependency and institutional theory, two open-natural system frameworks, are utilized to predict that Florida's circuit courts have become more efficient over the period since the implementation of Revision 7. The efficiency outcomes are expected to be unequal across circuit sizes. Integrating a Florida debate to a larger one that transcends time and culture, productivity changes are expected to be a function of the number of judges that a circuit adds within a given year, controlling for other factors. The results of the study methodologies--data envelopment analysis, Malmquist Productivity Index, hierarchal regression analysis and analysis of covariance--reveal that only 3 of 300 DMU's in Florida are technically efficient; the mean IOTA score is .76. The Florida circuits did not improve efficiency and productivity as expected, in fact becoming significantly less efficient over time as a function of Revision 7. Small and medium-sized circuits lost efficiency, large circuits showed no change and there was a significant interaction between circuit size and Revision 7 period. Within the system overall, productivity fell by 2.7%, most noticeably in the small and medium-sized circuits. The number of judges a circuit added explained 32.2% of the variance in total factor productivity change. The largest system productivity losses followed both Revision 7 intervention years and the addition of the most judges in a single year. Analysis of covariance revealed that productivity increased only when no judges were added to a circuit, regardless of circuit size or time period (+2.6%). The addition of a single judge reduced average productivity by 8.6%; adding two judges reduced productivity by 10.5% and adding 3 or more judges reduced productivity by 16.2%. As judges were added, productivity declined in circuits of all sizes, but the drop was more pronounced in the small and medium-sized circuits. None of the circuits showed an increase in productivity from 1993 to 2008. Revision 7 has not increased circuit court efficiency or productivity in Florida. It is recommended that efficiency and productivity analyses be included in resource allocation decisions such as adding judgeships. More data on court structures and process are needed. Efficiency and productivity measures show that the current level of circuit court judgeships is sufficient.
Show less - Date Issued
- 2010
- Identifier
- CFE0003457, ucf:52888
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003457
- Title
- CHARACTERIZATION OF THE NONLINEAR REFRACTIVE INDEX OF CARBONDISULFIDE OVER AN EXTENDED SPECTRAL AND TEMPORAL RANGE.
- Creator
-
Seidel, Marcus, Van Stryland, Eric, University of Central Florida
- Abstract / Description
-
The intensity dependent refractive index change of a medium is frequently described in terms of the product n2xI where n2 is the nonlinear refractive index and I the light intensity. The nonlinear refractive index is often treated as constant which is a reasonable assumption if the light interacts only with bound electrons. In the case of carbon disulfide (CS2) however, nuclear motions contribute to n2. These motions occur on the sub picosecond time scale and thus become especially relevant...
Show moreThe intensity dependent refractive index change of a medium is frequently described in terms of the product n2xI where n2 is the nonlinear refractive index and I the light intensity. The nonlinear refractive index is often treated as constant which is a reasonable assumption if the light interacts only with bound electrons. In the case of carbon disulfide (CS2) however, nuclear motions contribute to n2. These motions occur on the sub picosecond time scale and thus become especially relevant for ultrashort laser pulses. The neat liquid CS2 is studied because it exhibits a large nonlinear refractive index in comparison to other liquids. Therefore, it is employed in optical switching, optical limiting, and beam filamentation applications. This thesis presents effective n2 values for Gaussian shaped linearly polarized pulses with central wavelengths of 700nm. A theoretical model describing the time evolution of the material response is applied to distinguish between the instantaneous electronic, the ultrafast nuclear and the slow nuclear origins of the nonlinear refractive index. Moreover, the tensor nature of the material response function is studied by means of circularly polarized light. The relative magnitudes of bound electronic and nuclear contributions to n2 are experimentally determined. Eventually, the dispersion of the instantaneous electronic response is measured in the spectral range between 411nm and 1064nm.
Show less - Date Issued
- 2011
- Identifier
- CFE0004052, ucf:49141
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004052
