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Title: Design, Characterization and Analysis of Electrostatic Discharge (ESD) Protection Solutions in Emerging and Modern Technologies.
Creator: Liu, Wen, Liou, Juin, Yuan, Jiann-Shiun, Sundaram, Kalpathy, Shen, Zheng, Chen, Quanfang, University of Central Florida
Abstract / Description: Electrostatic Discharge (ESD) is a significant hazard to electronic components and systems. Based on a specific processing technology, a given circuit application requires a customized ESD consideration that includes the devices' operating voltage, leakage current, breakdown constraints, and footprint. As new technology nodes mature every 3-5 years, design of effective ESD protection solutions has become more and more challenging due to the narrowed design window, elevated electric field and...
Show moreElectrostatic Discharge (ESD) is a significant hazard to electronic components and systems. Based on a specific processing technology, a given circuit application requires a customized ESD consideration that includes the devices' operating voltage, leakage current, breakdown constraints, and footprint. As new technology nodes mature every 3-5 years, design of effective ESD protection solutions has become more and more challenging due to the narrowed design window, elevated electric field and current density, as well as new failure mechanisms that are not well understood. The endeavor of this research is to develop novel, effective and robust ESD protection solutions for both emerging technologies and modern complementary metal(-)oxide(-)semiconductor (CMOS) technologies.The Si nanowire field-effect transistors are projected by the International Technology Roadmap for Semiconductors as promising next-generation CMOS devices due to their superior DC and RF performances, as well as ease of fabrication in existing Silicon processing. Aiming at proposing ESD protection solutions for nanowire based circuits, the dimension parameters, fabrication process, and layout dependency of such devices under Human Body Mode (HBM) ESD stresses are studied experimentally in company with failure analysis revealing the failure mechanism induced by ESD. The findings, including design methodologies, failure mechanism, and technology comparisons should provide practical knowhow of the development of ESD protection schemes for the nanowire based integrated circuits. Organic thin-film transistors (OTFTs) are the basic elements for the emerging flexible, printable, large-area, and low-cost organic electronic circuits. Although there are plentiful studies focusing on the DC stress induced reliability degradation, the operation mechanism of OTFTs subject to ESD is not yet available in the literature and are urgently needed before the organic technology can be pushed into consumer market. In this work, the ESD operation mechanism of OTFT depending on gate biasing condition and dimension parameters are investigated by extensive characterization and thorough evaluation. The device degradation evolution and failure mechanism under ESD are also investigated by specially designed experiments. In addition to the exploration of ESD protection solutions in emerging technologies, efforts have also been placed in the design and analysis of a major ESD protection device, diode-triggered-silicon-controlled-rectifier (DTSCR), in modern CMOS technology (90nm bulk). On the one hand, a new type DTSCR having bi-directional conduction capability, optimized design window, high HBM robustness and low parasitic capacitance are developed utilizing the combination of a bi-directional silicon-controlled-rectifier and bi-directional diode strings. On the other hand, the HBM and Charged Device Mode (CDM) ESD robustness of DTSCRs using four typical layout topologies are compared and analyzed in terms of trigger voltage, holding voltage, failure current density, turn-on time, and overshoot voltage. The advantages and drawbacks of each layout are summarized and those offering the best overall performance are suggested at the end.
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Date Issued: 2012
Identifier: CFE0004571, ucf:49199
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004571

Title: MEDIA EFFECTS ON BODY IMAGE IN THE CONTEXT OF ENVIRONMENTAL AND INTERNAL INFLUENCES: WHAT MATTERS MOST?.
Creator: VanVonderen, Kristen, Kinnally, William, University of Central Florida
Abstract / Description: Media effects on body dissatisfaction is a long-studied issue; however, aspects of the research - such as those regarding cultivation theory and its effects on body image - are unclear or incomplete. This study attempts to clarify the relationship between cultivation and body dissatisfaction. Besides cultivation, social comparison theory is also examined because upward comparisons with media images and peers can shape and reinforce body image attitudes as well. Additionally, the study...
Show moreMedia effects on body dissatisfaction is a long-studied issue; however, aspects of the research - such as those regarding cultivation theory and its effects on body image - are unclear or incomplete. This study attempts to clarify the relationship between cultivation and body dissatisfaction. Besides cultivation, social comparison theory is also examined because upward comparisons with media images and peers can shape and reinforce body image attitudes as well. Additionally, the study examines the connection between media and body dissatisfaction by looking at a broader social context - one that includes other social/environmental influences, such as peer and parental attitudes, as well as internal influences such as self-esteem. A sample of 285 female undergraduate students completed media exposure, parental influence, peer influence, and self-esteem measures, as well as internalization of the thin-ideal and body dissatisfaction measures. Overall, the study found that while peer comparisons and self-esteem are associated with internalization of the thin ideal, they are not as powerful as the most significant indicators - media attitudes regarding weight and body shape and media comparisons. Contrastingly, peer comparisons and self-esteem were observed to be the strongest indicators of body dissatisfaction. These findings suggest that cultivation is directly associated with the internalization of the thin ideal. However, the cultivation of media messages may not have a direct effect on body dissatisfaction, as social/environmental influences and the internal variable of self-esteem proved to be the most significant indicators.
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Date Issued: 2011
Identifier: CFE0003995, ucf:48676
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003995

Title: Exploring Intensive Reading Intervention Teachers' Formal and Practical Knowledge of Beginning Reading Instruction Provided to At-Risk First Grade Readers.
Creator: Cortelyou, Kathryn, Biraimah, Karen, Kelley, Michelle, Beverly, Monifa, Clements, Taylar, University of Central Florida
Abstract / Description: This study was designed with two goals in mind. The first goal was to describe the formal and practical knowledge of intensive reading intervention teachers related to beginning reading instruction with at-risk first graders. A second goal was to understand any potential relationships between intensive reading teachers' practical knowledge and formal knowledge. These two goals framed the study's three research questions. To answer these three questions, the study was conducted in two phases....
Show moreThis study was designed with two goals in mind. The first goal was to describe the formal and practical knowledge of intensive reading intervention teachers related to beginning reading instruction with at-risk first graders. A second goal was to understand any potential relationships between intensive reading teachers' practical knowledge and formal knowledge. These two goals framed the study's three research questions. To answer these three questions, the study was conducted in two phases. Phase one included 32 participants, all of whom worked in the role of a K-2 intensive reading intervention teacher. Each of these 32 participants completed a background questionnaire and a paper/pencil Teacher Knowledge Assessment (TKA). The TKA measured participants' formal knowledge of beginning reading concepts. Participants' scores on the TKA were then rank-ordered from lowest to highest to help guide the selection of phase two participants. Eight teachers in all participated in phase two of the study dedicated to the study of teachers' practical knowledge of reading. Participants' practical knowledge of reading was explored through three activities including a semi-structured interview, a concept-mapping activity and a videotaped reading lesson. Data analysis revealed several important findings. Intensive reading intervention teachers in this study's sample differed in their formal knowledge of reading, measured by the TKA, and in their practical knowledge of reading, explored through interviews, concept-maps and reading lessons. The TKA revealed that study participants' held more formal knowledge of concepts related to phonology and phonics and less formal knowledge of concepts related to morphology and syllable types. Related to practical knowledge, data analysis revealed that the teachers in this sample differed in their knowledge of beginning reading with subject-matter knowledge accounting for most of the differences. These gaps in subject-matter knowledge also impacted this sample of teachers' use of instructional strategies and purposes of instruction. Data analysis also revealed insight into the relationships between this sample of teachers' formal and practical reading knowledge. In this sample, intensive reading intervention teachers with more formal knowledge of reading concepts as measured on the TKA demonstrated more evidence of these concepts within their instruction provided to at-risk first grade readers. The participants in this sample who had less formal knowledge of beginning reading as measured by the TKA demonstrated less evidence of these concepts within their instruction provided to at-risk first grade readers. Participants with less formal knowledge did accurately calibrate their knowledge of the concepts tested on the TKA but did not equate the lower scores to their practical knowledge and overall teaching efficacy. The findings from this study added several important contributions to the literature on teacher knowledge and beginning reading instruction. First, the study was unique in its focus on intensive reading intervention teachers, thus contributing new findings related to a specialized group of teachers. Secondly, this study contributed descriptions of teachers' practical knowledge with regards to beginning reading instruction. These descriptions are relatively absent in the current literature on teacher knowledge. Thirdly, the results from this study supported earlier findings in favor of a specialized body of subject-matter knowledge, especially related to beginning reading skills and concepts. Finally, the results contributed insight into the relationships between teachers' formal reading knowledge and practical reading knowledge.
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Date Issued: 2012
Identifier: CFE0004541, ucf:49260
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004541

Title: The Impact of Degraded Speech and Stimulus Familiarity in a Dichotic Listening Task.
Creator: Sinatra, Anne, Sims, Valerie, Hancock, Peter, Szalma, James, Chin, Matthew, Renk, Kimberly, University of Central Florida
Abstract / Description: It has been previously established that when engaged in a difficult attention intensive task, which involves repeating information while blocking out other information (the dichotic listening task), participants are often able to report hearing their own names in an unattended audio channel (Moray, 1959). This phenomenon, called the cocktail party effect is a result of words that are important to oneself having a lower threshold, resulting in less attention being necessary to process them ...
Show moreIt has been previously established that when engaged in a difficult attention intensive task, which involves repeating information while blocking out other information (the dichotic listening task), participants are often able to report hearing their own names in an unattended audio channel (Moray, 1959). This phenomenon, called the cocktail party effect is a result of words that are important to oneself having a lower threshold, resulting in less attention being necessary to process them (Treisman, 1960). The current studies examined the ability of a person who was engaged in an attention demanding task to hear and recall low-threshold words from a fictional story. These low-threshold words included a traditional alert word, (")fire(") and fictional character names from a popular franchise(-)Harry Potter. Further, the role of stimulus degradation was examined by including synthetic and accented speech in the task to determine how it would impact attention and performance.In Study 1 participants repeated passages from a novel that was largely unfamiliar to them, The Secret Garden while blocking out a passage from a much more familiar source, Harry Potter and the Deathly Hallows. Each unattended Harry Potter passage was edited so that it would include 4 names from the series, and the word (")fire(") twice. The type of speech present in the attended and unattended ears (Natural or Synthetic) was varied to examine the impact that processing a degraded speech would have on performance. The speech that the participant shadowed did not impact unattended recall, however it did impact shadowing accuracy. The speech type that was present in the unattended ear did impact the ability to recall low-threshold, Harry Potter information. When the unattended speech type was synthetic, significantly less Harry Potter information was recalled. Interestingly, while Harry Potter information was recalled by participants with both high and low Harry Potter experience, the traditional low-threshold word, (")fire(") was not noticed by participants. In order to determine if synthetic speech impeded the ability to report low-threshold Harry Potter names due to being degraded or simply being different than natural speech, Study 2 was designed. In Study 2 the attended (shadowed) speech was held constant as American Natural speech, and the unattended ear was manipulated. An accent which was different than the native accent of the participants was included as a mild form of degradation. There were four experimental stimuli which contained one of the following in the unattended ear: American Natural, British Natural, American Synthetic and British Synthetic. Overall, more unattended information was reported when the unattended channel was Natural than Synthetic. This implies that synthetic speech does take more working memory processing power than even an accented natural speech. Further, it was found that experience with the Harry Potter franchise played a role in the ability to report unattended Harry Potter information. Those who had high levels of Harry Potter experience, particularly with audiobooks, were able to process and report Harry Potter information from the unattended stimulus when it was British Natural. While, those with low Harry Potter experience were not able to report unattended Harry Potter information from this slightly degraded stimulus. Therefore, it is believed that the previous audiobook experience of those in the high Harry Potter experience group acted as training and resulted in less working memory being necessary to encode the unattended Harry Potter information. A pilot study was designed in order to examine the impact of story familiarity in the attended and unattended channels of a dichotic listening task. In the pilot study, participants shadowed a Harry Potter passage (familiar) in one condition with a passage from The Secret Garden (unfamiliar) playing in the unattended ear. A second condition had participants shadowing The Secret Garden (unfamiliar) with a passage from Harry Potter (familiar) present in the unattended ear. There was no significant difference in the number of unattended names recalled. Those with low Harry Potter experience reported significantly less attended information when they shadowed Harry Potter than when they shadowed The Secret Garden. Further, there appeared to be a trend such that those with high Harry Potter experience were reporting more attended information when they shadowed Harry Potter than The Secret Garden. This implies that experience with a franchise and characters may make it easier to recall information about a passage, while lack of experience provides no assistance. Overall, the results of the studies indicate that we do treat fictional characters in a way similarly to ourselves. Names and information about fictional characters were able to break through into attention during a task that required a great deal of attention. The experience one had with the characters also served to assist the working memory in processing the information in degraded circumstances. These results have important implications for training, design of alerts, and the use of popular media in the classroom.
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Date Issued: 2012
Identifier: CFE0004256, ucf:49535
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004256

Title: Incorporating Remotely Sensed Data into Coastal Hydrodynamic Models: Parameterization of Surface Roughness and Spatio-Temporal Validation of Inundation Area.
Creator: Medeiros, Stephen, Hagen, Scott, Weishampel, John, Wang, Dingbao, Yeh, Gour-Tsyh, University of Central Florida
Abstract / Description: This dissertation investigates the use of remotely sensed data in coastal tide and inundation models, specifically how these data could be more effectively integrated into model construction and performance assessment techniques. It includes a review of numerical wetting and drying algorithms, a method for constructing a seamless digital terrain model including the handling of tidal datums, an investigation into the accuracy of land use / land cover (LULC) based surface roughness...
Show moreThis dissertation investigates the use of remotely sensed data in coastal tide and inundation models, specifically how these data could be more effectively integrated into model construction and performance assessment techniques. It includes a review of numerical wetting and drying algorithms, a method for constructing a seamless digital terrain model including the handling of tidal datums, an investigation into the accuracy of land use / land cover (LULC) based surface roughness parameterization schemes, an application of a cutting edge remotely sensed inundation detection method to assess the performance of a tidal model, and a preliminary investigation into using 3-dimensional airborne laser scanning data to parameterize surface roughness.A thorough academic review of wetting and drying algorithms employed by contemporary numerical tidal models was conducted. Since nearly all population centers and valuable property are located in the overland regions of the model domain, the coastal models must adequately describe the inundation physics here. This is accomplished by techniques that generally fall into four categories: Thin film, Element removal, Depth extrapolation, and Negative depth. While nearly all wetting and drying algorithms can be classified as one of the four types, each model is distinct and unique in its actual implementation.The use of spatial elevation data is essential to accurate coastal modeling. Remotely sensed LiDAR is the standard data source for constructing topographic digital terrain models (DTM). Hydrographic soundings provide bathymetric elevation information. These data are combined to form a seamless topobathy surface that is the foundation for distributed coastal models. A three-point inverse distance weighting method was developed in order to account for the spatial variability of bathymetry data referenced to tidal datums. This method was applied to the Tampa Bay region of Florida in order to produce a seamless topobathy DTM.Remotely sensed data also contribute to the parameterization of surface roughness. It is used to develop land use / land cover (LULC) data that is in turn used to specify spatially distributed bottom friction and aerodynamic roughness parameters across the model domain. However, these parameters are continuous variables that are a function of the size, shape and density of the terrain and above-ground obstacles. By using LULC data, much of the variation specific to local areas is generalized due to the categorical nature of the data. This was tested by comparing surface roughness parameters computed based on field measurements to those assigned by LULC data at 24 sites across Florida. Using a t-test to quantify the comparison, it was proven that the parameterizations are significantly different. Taking the field measured parameters as ground truth, it is evident that parameterizing surface roughness based on LULC data is deficient.In addition to providing input parameters, remotely sensed data can also be used to assess the performance of coastal models. Traditional methods of model performance testing include harmonic resynthesis of tidal constituents, water level time series analysis, and comparison to measured high water marks. A new performance assessment that measures a model's ability to predict the extent of inundation was applied to a northern Gulf of Mexico tidal model. The new method, termed the synergetic method, is based on detecting inundation area at specific points in time using satellite imagery. This detected inundation area is compared to that predicted by a time-synchronized tidal model to assess the performance of model in this respect. It was shown that the synergetic method produces performance metrics that corroborate the results of traditional methods and is useful in assessing the performance of tidal and storm surge models. It was also shown that the subject tidal model is capable of correctly classifying pixels as wet or dry on over 85% of the sample areas.Lastly, since it has been shown that parameterizing surface roughness using LULC data is deficient, progress toward a new parameterization scheme based on 3-dimensional LiDAR point cloud data is presented. By computing statistics for the entire point cloud along with the implementation of moving window and polynomial fit approaches, empirical relationships were determined that allow the point cloud to estimate surface roughness parameters. A multi-variate regression approach was chosen to investigate the relationship(s) between the predictor variables (LiDAR statistics) and the response variables (surface roughness parameters). It was shown that the empirical fit is weak when comparing the surface roughness parameters to the LiDAR data. The fit was improved by comparing the LiDAR to the more directly measured source terms of the equations used to compute the surface roughness parameters. Future work will involve using these empirical relationships to parameterize a model in the northern Gulf of Mexico and comparing the hydrodynamic results to those of the same model parameterized using contemporary methods. In conclusion, through the work presented herein, it was demonstrated that incorporating remotely sensed data into coastal models provides many benefits including more accurate topobathy descriptions, the potential to provide more accurate surface roughness parameterizations, and more insightful performance assessments. All of these conclusions were achieved using data that is readily available to the scientific community and, with the exception of the Synthetic Aperture Radar (SAR) from the Radarsat-1 project used in the inundation detection method, are available free of charge. Airborne LiDAR data are extremely rich sources of information about the terrain that can be exploited in the context of coastal modeling. The data can be used to construct digital terrain models (DTMs), assist in the analysis of satellite remote sensing data, and describe the roughness of the landscape thereby maximizing the cost effectiveness of the data acquisition.
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Date Issued: 2012
Identifier: CFE0004271, ucf:49506
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004271

Title: ELECTRON TRANSPORT IN SINGLE MOLECULE MAGNET TRANSISTORS AND OPTICAL LAMBDA TRANSITIONS IN THE NITROGEN-VACANCY CENTER IN DIAMOND.
Creator: Gonzalez, Gabriel, Leuenberger, Michael, University of Central Florida
Abstract / Description: This thesis presents some theoretical studies dealing with quantum interference effects in electron transport through single molecule magnet transistors and a study on optical non-conserving spin transitions in the Nitrogen-vacancy center in diamond. The thesis starts with a brief general introduction to the physics of quantum transport through single electron transistors. Afterwards, the main body of the thesis is divided into three studies: (i) In chapter (2) we describe the properties of...
Show moreThis thesis presents some theoretical studies dealing with quantum interference effects in electron transport through single molecule magnet transistors and a study on optical non-conserving spin transitions in the Nitrogen-vacancy center in diamond. The thesis starts with a brief general introduction to the physics of quantum transport through single electron transistors. Afterwards, the main body of the thesis is divided into three studies: (i) In chapter (2) we describe the properties of single molecule magnets and the Berry phase interference present in this nanomagnets. We then propose a way to detect quantum interference experimentally in the current of a single molecule magnet transistor using polarized leads. We apply our theoretical results to the newly synthesized nanomagnet Ni4. (ii) In chapter (3) we review the Kondo effect and present a microscopic derivation of the Kondo Hamiltonian suitable for full and half integer spin nanomagnets. We then calculate the conductance of the single molecule magnet transistor in the presence of the Kondo effect for Ni4 and show how the Berry phase interference becomes temperature dependent. (iii) We conclude in chapter (4) with a theoretical study of the single Nitrogen vacancy defect center in diamond. We show that it is possible to have spin non-conserving transitions via the hyperfine interaction and propose a way to write and read quantum information using circularly polarized light by means of optical Lambda transitions in this solid state system.
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Date Issued: 2009
Identifier: CFE0002740, ucf:48179
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002740

Title: PATTERNED CELL CULTURES FOR HIGH THROUGHPUT STUDIES OF CELL ELECTROPHYSIOLOGY AND DRUG SCREENING APPLICATIONS.
Creator: Natarajan, Anupama, Hickman, James, University of Central Florida
Abstract / Description: Over the last decade, the field of tissue and bio-engineering has seen an increase in the development of in vitro high-throughput hybrid systems that can be used to understand cell function and behavior at the cellular and tissue levels. These tools would have a wide array of applications including for implants, drug discovery, and toxicology, as well as for studying cell developmental behavior and as disease models. Currently, there are a limited number of efficient, functional drug...
Show moreOver the last decade, the field of tissue and bio-engineering has seen an increase in the development of in vitro high-throughput hybrid systems that can be used to understand cell function and behavior at the cellular and tissue levels. These tools would have a wide array of applications including for implants, drug discovery, and toxicology, as well as for studying cell developmental behavior and as disease models. Currently, there are a limited number of efficient, functional drug screening assays in the pharmacology industry and studies of cell-surface interactions are complicated and invasive. Most cell physiology studies are performed using conventional patch-clamp techniques or random networks cultured on silicon devices such as Microelectrode Arrays (MEAs) and Field Effect transistors (FETs). The objective of this study was to develop high-throughput in vitro platforms that could be used to analyze cell function and their response to various stimuli. Our hypothesis was that by utilizing surface modification to provide external guidance cues for various cell types and by controlling the cell environment in terms of culture conditions, we could develop an in vitro hybrid platform for sensing and testing applications. Such a system would not only give information regarding the surface effects on the growth and behavior of cells for implant development applications, but also allow for the study of vital cell physiology parameters like conduction velocity in cardiomyocytes and synaptic plasticity in neuronal networks. This study outlines the development of these in vitro high throughput systems that have varied applications ranging from tissue engineering to drug development. We have developed a simple and relatively high-throughput method in order to test the physiological effects of varying chemical environments on rat embryonic cardiac myocytes in order to model the degradation effects of polymer scaffolds. Our results, using our simple test system, are in agreement with earlier observations that utilized a complex 3D biodegradable scaffold. Thus, surface functionalization with self-assembled monolayers combined with histological/physiological testing could be a relatively high throughput method for biocompatibility studies and for the optimization of the material/tissue interface in tissue engineering. Traditional multielectrode extracellular recording methods were combined with surface patterning of cardiac myocyte monolayers to enhance the information content of the method; for example, to enable the measurement of conduction velocity, refractory period after action potentials or to create a functional reentry model. Two drugs, 1-Heptanol, a gap junction blocker, and Sparfloxacin, a fluoroquinone antibiotic, were tested in this system. 1-Heptanol administration resulted in a marked reduction in conduction velocity, whereas Sparfloxacin caused rapid, irregular and unsynchronized activity, indicating fibrillation. As shown in these experiments, the patterning of cardiac myocyte monolayers increased the information content of traditional multielectrode measurements. Patterning techniques with self-assembled monolayers on microelectrode arrays were also used to study the physiological properties of hippocampal networks with functional uni-directional connectivity, developed to study the mono-synaptic connections found in the dentate gyrus. Results indicate that changes in synaptic connectivity and strength were chemically induced in these patterned hippocampal networks. This method is currently being used for studying long term potentiation at the cellular level. For this purpose, two cell patterns were optimized for cell migration onto the pattern as demonstrated by time lapse studies, and for supporting the best pattern formation and cell survival on these networks. The networks formed mature interconnected spiking neurons. In conclusion, this study demonstrates the development and testing of in vitro high-throughput systems that have applications in drug development, understanding disease models and tissue engineering. It can be further developed for use with human cells to have a more predictive value than existing complex, expensive and time consuming methods.
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Date Issued: 2010
Identifier: CFE0003384, ucf:48437
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003384

Title: PERCEPTIONS AND THEIR ROLE IN CONSUMER DECISION-MAKING.
Creator: Khaddaria, Raman, Gerking, Shelby, University of Central Florida
Abstract / Description: This dissertation is an empirical investigation into the roles that different quantifiable and measurable perceptions play in defining individual behavior across a variety of decision-making contexts. In particular, the focus lies on smokers and the choices they make with regard to smoking and beyond. Chapter 1 analyzes a nationally representative sample of adults (23 years and older) in the United States, pertaining to the Annenberg Perception of Tobacco Risk Survey II (1999-2000). It is...
Show moreThis dissertation is an empirical investigation into the roles that different quantifiable and measurable perceptions play in defining individual behavior across a variety of decision-making contexts. In particular, the focus lies on smokers and the choices they make with regard to smoking and beyond. Chapter 1 analyzes a nationally representative sample of adults (23 years and older) in the United States, pertaining to the Annenberg Perception of Tobacco Risk Survey II (1999-2000). It is observed that three dimensions to smoking behavior viz., risk, temporality and addiction, interact to determine the smoking status of an individual. Although previous studies mostly looked into each of these dimensions in isolation, in this chapter, we empirically illustrate how perceptions on risk, time dimensions and addiction, jointly influence the smoking behavior of adults. Chapter 2 casts the smoker in the role of a parent and explores parental behavior towards the general health-risks facing their children. Using the dataset from a survey (2009), conducted in Orlando, Florida, on parents, having at least one child aged between 1 and 16 years, the chapter arrives at two findings relevant for policy: i) In each of the 'smoker' and 'non-smoker' parent categories, parents exhibit equal concern for themselves and their children, and ii) the level of concern shown by smoker-parents, towards health-risks faced by their children, is the same as that shown by their non-smoking counterparts. The analysis in this chapter also affirms the need to incorporate subjective risk assessment in willingness-to-pay (WTP) exercises to facilitate a deeper behavioral analysis of health risk valuation. Lastly, in Chapter 3, we focus on the issue of quantitative assessment of the perception of health risks from smoking. Particular interest lies in understanding how variants of a metric - namely, a survey question - have been employed in academic studies and industry-surveys, in order to measure smoking-related risk-perceptions. In the process of reviewing select tobacco-industry survey records, we analyze the implications of different features of this metric, (e.g., use of a 'probe', the 'Don't Know' option), and various interview modes (e.g. telephonic, face-to-face), for the estimates of perceived risk arrived at in these studies. The review makes clear that two aspects of health risks from smoking - the risk of contracting a smoking-related disease, as against the risk of prematurely dying from it conditional upon getting affected - have not been jointly explored so far. The dataset obtained from the Family Heart Disease and Prevention Survey (November 2010-March 2011), provides a unique opportunity to explore these two kinds of probabilities, particularly with regard to the risks of lung-cancer from smoking. Chapter 3 concludes by illustrating how individuals evaluate both these aspects of health-risks. While the probability of getting lung-cancer is found to be overestimated in conjunction with previous studies, the conditional probability of premature death is severely underestimated. Additionally, it is found that individuals' subjective assessments of either of these risk aspects predict smoking behavior in an identical manner. This calls into question the so-called 'rationality' of smoking decisions with implications for policies designed for the control of tobacco consumption.
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Date Issued: 2011
Identifier: CFE0003918, ucf:48736
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003918

Title: Doctoral Supervision: An Analysis of Doctoral Candidates' and Graduates' Perception of Supervisory Practices.
Creator: Tapoler, Colton, Taylor, Rosemarye, Vitale, Thomas, Doherty, Walter, Marshall, Nancy, University of Central Florida
Abstract / Description: The purpose of this study was to collect and examine the reported supervisory practices experienced by professional doctoral candidates in the last year of their program, and recent program graduates, within the last three years, from across multiple disciplines. Doctoral supervisors, specifically in the United States, are not usually provided a set of practices or concrete training prior to advising doctoral candidates (Walker, 2008, p. 35). With this in mind, and the limited amount of...
Show moreThe purpose of this study was to collect and examine the reported supervisory practices experienced by professional doctoral candidates in the last year of their program, and recent program graduates, within the last three years, from across multiple disciplines. Doctoral supervisors, specifically in the United States, are not usually provided a set of practices or concrete training prior to advising doctoral candidates (Walker, 2008, p. 35). With this in mind, and the limited amount of research available on doctoral supervision in professional doctoral programs in the United States, it was critical to analyze the experienced supervision of professional doctoral candidates and its perceived effectiveness. Current candidates and recent graduates were asked to participate in interviews based on the supervision they received. Ultimately, 3 current candidates and 15 recent graduates were interviewed for this study. The interviews were transcribed verbatim and then analyzed using grounded theory (Corbin (&) Strauss, 1990). The interviews were carefully analyzed for emerging trends that went on to represent individual supervisory practices, or concepts. After several additional readings the concepts were grouped together based on similarity into categories. Finally, the concepts and categories were analyzed for connections to candidate success, which developed into the findings of this study.Ultimately, candidates and recent graduates discussed 19 supervisory practices. The 19 supervisory practices, or concepts, were: frequency of communication, quality of communication, mode of communication, accessibility, feedback, the use of articles and research, the use of a timeline for candidates, utilization of the supervisor's existing expertise, workshop offerings, use of the supervisor's network, building a personal connection, showing enthusiasm, candor, trust, encouragement, autonomy, guidance, providing advice academically, and developing a colleague-to-colleague relationship. Each of the 19 concepts was discussed as having varying levels of impact on candidates successfully completing their programs. Doctoral supervisors, and doctoral programs, should consider the implementation of these supervisory practices and the training that helps supervisors develop their supervisory experiences.
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Date Issued: 2017
Identifier: CFE0006667, ucf:51252
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006667

Title: Exploration and development of crash modification factors and functions for single and multiple treatments.
Creator: Park, Juneyoung, Abdel-Aty, Mohamed, Radwan, Essam, Eluru, Naveen, Wang, Chung-Ching, Lee, JaeYoung, University of Central Florida
Abstract / Description: Traffic safety is a major concern for the public, and it is an important component of the roadway management strategy. In order to improve highway safety, extensive efforts have been made by researchers, transportation engineers, Federal, State, and local government officials. With these consistent efforts, both fatality and injury rates from road traffic crashes in the United States have been steadily declining over the last six years (2006~2011). However, according to the National Highway...
Show moreTraffic safety is a major concern for the public, and it is an important component of the roadway management strategy. In order to improve highway safety, extensive efforts have been made by researchers, transportation engineers, Federal, State, and local government officials. With these consistent efforts, both fatality and injury rates from road traffic crashes in the United States have been steadily declining over the last six years (2006~2011). However, according to the National Highway Traffic Safety Administration (NHTSA, 2013), 33,561 people died in motor vehicle traffic crashes in the United States in 2012, compared to 32,479 in 2011, and it is the first increase in fatalities since 2005. Moreover, in 2012, an estimated 2.36 million people were injured in motor vehicle traffic crashes, compared to 2.22 million in 2011. Due to the demand of highway safety improvements through systematic analysis of specific roadway cross-section elements and treatments, the Highway Safety Manual (HSM) (AASHTO, 2010) was developed by the Transportation Research Board (TRB) to introduce a science-based technical approach for safety analysis. One of the main parts in the HSM, Part D, contains crash modification factors (CMFs) for various treatments on roadway segments and at intersections. A CMF is a factor that can estimate potential changes in crash frequency as a result of implementing a specific treatment (or countermeasure). CMFs in Part D have been developed using high-quality observational before-after studies that account for the regression to the mean threat. Observational before-after studies are the most common methods for evaluating safety effectiveness and calculating CMFs of specific roadway treatments. Moreover, cross-sectional method has commonly been used to derive CMFs since it is easier to collect the data compared to before-after methods.Although various CMFs have been calculated and introduced in the HSM, still there are critical limitations that are required to be investigated. First, the HSM provides various CMFs for single treatments, but not CMFs for multiple treatments to roadway segments. The HSM suggests that CMFs are multiplied to estimate the combined safety effects of single treatments. However, the HSM cautions that the multiplication of the CMFs may over- or under-estimate combined effects of multiple treatments. In this dissertation, several methodologies are proposed to estimate more reliable combined safety effects in both observational before-after studies and the cross-sectional method. Averaging two best combining methods is suggested to use to account for the effects of over- or under- estimation. Moreover, it is recommended to develop adjustment factor and function (i.e. weighting factor and function) to apply to estimate more accurate safety performance in assessing safety effects of multiple treatments. The multivariate adaptive regression splines (MARS) modeling is proposed to avoid the over-estimation problem through consideration of interaction impacts between variables in this dissertation. Second, the variation of CMFs with different roadway characteristics among treated sites over time is ignored because the CMF is a fixed value that represents the overall safety effect of the treatment for all treated sites for specific time periods. Recently, few studies developed crash modification functions (CMFunctions) to overcome this limitation. However, although previous studies assessed the effect of a specific single variable such as AADT on the CMFs, there is a lack of prior studies on the variation in the safety effects of treated sites with different multiple roadway characteristics over time. In this study, adopting various multivariate linear and nonlinear modeling techniques is suggested to develop CMFunctions. Multiple linear regression modeling can be utilized to consider different multiple roadway characteristics. To reflect nonlinearity of predictors, a regression model with nonlinearizing link function needs to be developed. The Bayesian approach can also be adopted due to its strength to avoid the problem of over fitting that occurs when the number of observations is limited and the number of variables is large. Moreover, two data mining techniques (i.e. gradient boosting and MARS) are suggested to use 1) to achieve better performance of CMFunctions with consideration of variable importance, and 2) to reflect both nonlinear trend of predictors and interaction impacts between variables at the same time. Third, the nonlinearity of variables in the cross-sectional method is not discussed in the HSM. Generally, the cross-sectional method is also known as safety performance functions (SPFs) and generalized linear model (GLM) is applied to estimate SPFs. However, the estimated CMFs from GLM cannot account for the nonlinear effect of the treatment since the coefficients in the GLM are assumed to be fixed. In this dissertation, applications of using generalized nonlinear model (GNM) and MARS in the cross-sectional method are proposed. In GNMs, the nonlinear effects of independent variables to crash analysis can be captured by the development of nonlinearizing link function. Moreover, the MARS accommodate nonlinearity of independent variables and interaction effects for complex data structures. In this dissertation, the CMFs and CMFunctions are estimated for various single and combination of treatments for different roadway types (e.g. rural two-lane, rural multi-lane roadways, urban arterials, freeways, etc.) as below:1) Treatments for mainline of roadway: - adding a thru lane, conversion of 4-lane undivided roadways to 3-lane with two-way left turn lane (TWLTL)2) Treatments for roadway shoulder: - installing shoulder rumble strips, widening shoulder width, adding bike lanes, changing bike lane width, installing roadside barriers3) Treatments related to roadside features: - decrease density of driveways, decrease density of roadside poles, increase distance to roadside poles, increase distance to trees Expected contributions of this study are to 1) suggest approaches to estimate more reliable safety effects of multiple treatments, 2) propose methodologies to develop CMFunctions to assess the variation of CMFs with different characteristics among treated sites, and 3) recommend applications of using GNM and MARS to simultaneously consider the interaction impact of more than one variables and nonlinearity of predictors.Finally, potential relevant applications beyond the scope of this research but worth investigation in the future are discussed in this dissertation.
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Date Issued: 2015
Identifier: CFE0005861, ucf:50914
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005861

Title: Modeling Repair Patches of Ship Hull and Studying the Effect of Their Orientation on Stresses.
Creator: Enwegy, Halima, Moslehy, Faissal, Kassab, Alain, Bai, Yuanli, University of Central Florida
Abstract / Description: The hull is the most important structural part of any maritime vessel. It must be adequately designed to withstand the harsh sailing environmental conditions and associated forces. In the past, the basic material used to manufacture the ship hull was wood, where the hull was usually shaped as cylindrical wooden shanks. In the present, hull designs have developed to steel columns or stiffened panels that are made of different types of materials. Panels that are stiffened orthogonally in two or...
Show moreThe hull is the most important structural part of any maritime vessel. It must be adequately designed to withstand the harsh sailing environmental conditions and associated forces. In the past, the basic material used to manufacture the ship hull was wood, where the hull was usually shaped as cylindrical wooden shanks. In the present, hull designs have developed to steel columns or stiffened panels that are made of different types of materials. Panels that are stiffened orthogonally in two or more directions and have nine independent material constants are defined as orthotropic panels, and they achieve high specific strength.This thesis presents the effect of different patch orientations on the resulting strain and stress concentrations at the area of interaction between the panel and the patch. As it is known, the behavior of stiffened plates is affected by several important parameters, e.g., length to width ratio of the panel, stiffener geometry and spacing, aspect ratio for plates between stiffeners, plate slenderness, von Mises stresses, initial distortions, boundary conditions, and type of loading. A finite element model of the ship hull has been developed and run on ABAQUS (commercially available finite element software). The stiffened panel and patch are modeled as equivalent orthotropic plates made of steel. The panel edges are considered to be simply supported, and uniaxial tension was applied to the equivalent stiffened panel in addition to the lateral pressure (from water interaction). The developed model successfully predicted the optimal orientation of the panel for maximum stress concentration reduction. Moreover, in order to minimize the severe conditions caused by the mismatch that occurs if the material properties of the patch and the panel are the same during the patching process, it is necessary to stiffened the patch more than the panel. The developed model also suggested that an isotropic layer be added at the interaction to decrease the severity of arising stresses.
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Date Issued: 2014
Identifier: CFE0005162, ucf:50701
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005162

Title: Effects of Signal Probability on Multitasking-Based Distraction in Driving, Cyberattack (&) Battlefield Simulation.
Creator: Sawyer, Benjamin, Karwowski, Waldemar, Hancock, Peter, Xanthopoulos, Petros, University of Central Florida
Abstract / Description: Multitasking-based failures of perception and action are the focus of much research in driving, where they are attributed to distraction. Similar failures occur in contexts where the construct of distraction is little used. Such narrow application was attributed to methodology which cannot precisely account for experimental variables in time and space, limiting distraction's conceptual portability to other contexts. An approach based upon vigilance methodology was forwarded as a solution, and...
Show moreMultitasking-based failures of perception and action are the focus of much research in driving, where they are attributed to distraction. Similar failures occur in contexts where the construct of distraction is little used. Such narrow application was attributed to methodology which cannot precisely account for experimental variables in time and space, limiting distraction's conceptual portability to other contexts. An approach based upon vigilance methodology was forwarded as a solution, and highlighted a fundamental human performance question: Would increasing the signal probability (SP) of a secondary task increase associated performance, as is seen in the prevalence effect associated with vigilance tasks? Would it reduce associated performance, as is seen in driving distraction tasks? A series of experiments weighed these competing assumptions. In the first, a psychophysical task, analysis of accuracy and response data revealed an interaction between the number of concurrent tasks and SP of presented targets. The question was further tested in the applied contexts of driving, cyberattack and battlefield target decision-making. In line with previous prevalence effect inquiry, presentation of stimuli at higher SP led to higher accuracy. In line with existing distraction work, performance of higher numbers of concurrent tasks tended to elicit slower response times. In all experiments raising either number of concurrent tasks or SP of targets resulted in greater subjective workload, as measured by the NASA TLX, even when accompanied by improved accuracy. It would seem that (")distraction(") in previous experiments has been an aggregate effect including both delayed response time and prevalence-based accuracy effects. These findings support the view that superior experimental control of SP reveals nomothetic patterns of performance that allow better understanding and wider application of the distraction construct both within and in diverse contexts beyond driving.
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Date Issued: 2015
Identifier: CFE0006388, ucf:51522
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006388

Title: Hierarchical Corridor Safety Analysis Using Multiple Approaches.
Creator: Alarifi, Saif, Abdel-Aty, Mohamed, Tatari, Omer, Kuo, Pei-Fen, University of Central Florida
Abstract / Description: Traffic crashes are a major cause of concern globally. Extensive efforts from transportation professionals have been made to investigate new methods to identify the contributing factors to crashes at various locations on the road network. Corridors, among other road network's components, play a vital role in moving people and goods between primary zones in different areas, and the safety and operational improvements of them have been the focus of many studies since they carry the most traffic...
Show moreTraffic crashes are a major cause of concern globally. Extensive efforts from transportation professionals have been made to investigate new methods to identify the contributing factors to crashes at various locations on the road network. Corridors, among other road network's components, play a vital role in moving people and goods between primary zones in different areas, and the safety and operational improvements of them have been the focus of many studies since they carry the most traffic on the road network. Corridors contain mainly intersections and segments, and previous corridor studies have focused on a sole type of road entity. Having both components while analyzing corridors in addition to corridor-level variables in a hierarchical joint model framework would provide a comprehensive understanding of the existing safety problems along corridors. Therefore, this research aims to provide a complete understanding of the contributing factors to crashes at intersections and segments along corridors. In addition, it explores the associated crash risk factors with crash counts of different types and severity levels. The results reveal that accounting for the variations in traffic volumes and roadway characteristics, by estimating the model with random parameters, across corridors improved the model's performance. Also, the results confirm the importance of accounting for the spatial autocorrelation between road entities along the same corridor, and the adjacency-based first-order neighboring structure provides the best fit for the data among the other neighboring structures. Furthermore, it was found that the significant variables and their magnitudes are different across crash types and severity levels. Also, road designers and engineers should carefully identify the optimal number and location of driveways, median openings, and access points within the influence area of intersections since they significantly affect crashes along corridors. Lastly, this research suggests and justifies considering the proposed hierarchical joint model for future corridor studies
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Date Issued: 2018
Identifier: CFE0006967, ucf:51666
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006967

Title: Characterization of gold black and its application in un-cooled infrared detectors.
Creator: Panjwani, Deep, Peale, Robert, Chow, Lee, Del Barco, Enrique, Schoenfeld, Winston, University of Central Florida
Abstract / Description: Gold black porous coatings were thermally evaporated in the chamber backfilled with inert gas pressure and their optical properties were studied in near-far-IR wavelengths. The porosities of coatings were found to be extremely high around ~ 99%. Different approaches of effective medium theories such as Maxwell-Garnett, Bruggeman, Landau-Lifshitz-Looyenga and Bergman Formalism were utilized to calculate refractive index (n) and extinction coefficient (k). The aging induced changes on...
Show moreGold black porous coatings were thermally evaporated in the chamber backfilled with inert gas pressure and their optical properties were studied in near-far-IR wavelengths. The porosities of coatings were found to be extremely high around ~ 99%. Different approaches of effective medium theories such as Maxwell-Garnett, Bruggeman, Landau-Lifshitz-Looyenga and Bergman Formalism were utilized to calculate refractive index (n) and extinction coefficient (k). The aging induced changes on electrical and optical properties were studied in regular laboratory conditions using transmission electron microscopy, Fourier transform infrared spectroscopy, and fore-probe electrical measurements. A significant decrease in electrical resistance in as deposited coating was found to be consistent with changes in the granular structure with aging at room temperature. Electrical relaxation model was applied to calculate structural relaxation time in the coatings prepared with different porosities. Interestingly, with aging, absorptance of the coatings improved, which is explained using conductivity form of Bergman Formulism. Underlying aim of this work was to utilize gold blacks to improve sensitivity in un-cooled IR sensors consist of pixel arrays. To achieve this, fragile gold blacks were patterned on sub-mm length scale areas using both stenciling and conventional photolithography. Infrared spectral imaging with sub-micron spatial resolution revealed the spatial distribution of absorption across the gold black patterns produced with both the methods. Initial experiments on VOx-Au bolometers showed that, gold black improved the responsivity by 42%. This work successfully establishes promising role of gold black coatings in commercial un-cooled infrared detectors.
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Date Issued: 2015
Identifier: CFE0005680, ucf:50197
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005680

Title: An On-orbit Calibration Procedure for Spaceborne Microwave Radiometers Using Special Spacecraft Attitude Maneuvers.
Creator: Farrar, Spencer, Jones, W Linwood, Mikhael, Wasfy, Wahid, Parveen, Gaiser, Peter, University of Central Florida
Abstract / Description: This dissertation revisits, develops, and documents methods that can be used to calibrate spaceborne microwave radiometers once in orbit. The on-orbit calibration methods discussed within this dissertation can provide accurate and early results by utilizing Calibration Attitude Maneuvers (CAM), which encompasses Deep Space Calibration (DSC) and a new use of the Second Stokes (SS) analysis that can provide early and much needed insight on the performance of the instrument. This dissertation...
Show moreThis dissertation revisits, develops, and documents methods that can be used to calibrate spaceborne microwave radiometers once in orbit. The on-orbit calibration methods discussed within this dissertation can provide accurate and early results by utilizing Calibration Attitude Maneuvers (CAM), which encompasses Deep Space Calibration (DSC) and a new use of the Second Stokes (SS) analysis that can provide early and much needed insight on the performance of the instrument. This dissertation describes pre-existing and new methods of using DSC maneuvers as well as a simplified use of the SS procedure. Over TRMM's 17 years of operation it has provided invaluable data and has performed multiple CAMs over its lifetime. These maneuvers are analyzed to implement on-orbit calibration procedures that will be applied for future missions. In addition, this research focuses on the radiometric calibration of TMI that will be incorporated in the final processing (Archive/Legacy of the NASA TMI 1B11 brightness temperature data product). This is of importance since TMI's 17-year sensor data record must be vetted of all known calibration errors so to provide the final stable data for science users, specifically, climatological data records.
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Date Issued: 2015
Identifier: CFE0005611, ucf:50208
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005611

Title: EFFECTIVE SCHOOL CHARACTERISTICS AND STUDENT ACHIEVEMENT CORRELATES AS PERCEIVED BY TEACHERS IN AMERICAN STYLE INTERNATIONAL SCHOOLS.
Creator: Doran, James, Allen, Kay, University of Central Florida
Abstract / Description: The purpose of this study is to investigate the relationships between effective school characteristics and norm referenced standardized test scores in American-style international schools. In contrast to schools in traditional effective schools research, international schools typically have middle to high SES families, and display average to above average achievement. Eleven effective school characteristics were identified and correlated with standardized test scores for grades 4, 6, and 8...
Show moreThe purpose of this study is to investigate the relationships between effective school characteristics and norm referenced standardized test scores in American-style international schools. In contrast to schools in traditional effective schools research, international schools typically have middle to high SES families, and display average to above average achievement. Eleven effective school characteristics were identified and correlated with standardized test scores for grades 4, 6, and 8 and high school SAT scores. Data was gathered from an online teacher questionnaire designed for this study. All eleven characteristics were present in high performing international schools while frequent analysis of student progress, high academic expectations and positive school environment were more prominent. Positive school environment, high academic expectations, strong instructional leadership and cultural diversity were chosen as important characteristics of an effective international school. Learning time is maximized was the only characteristic that was significantly correlated with achievement and only in grades 4, 6 and 8. There was no statistically significant relationship found between norm referenced test scores and the aggregate effective school characteristics score.
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Date Issued: 2004
Identifier: CFE0000245, ucf:46244
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000245

Title: A Holistic Analysis of the Long-Term Challenges (&) Potential Benefits of the Green Roof, Solar PV Roofing, and GRIPV Roofing Markets in Orlando, Florida.
Creator: Kelly, Carolina, Tatari, Omer, Oloufa, Amr, Mayo, Talea, Zheng, Qipeng, University of Central Florida
Abstract / Description: Green roofs and roof-mounted solar PV arrays have a wide range of environmental and economic benefits, including significantly longer roof lifetimes, reductions in urban runoff, mitigation of the urban heat island (UHI) effect, reduced electricity demand and energy dependence, and/or reduced emissions of greenhouse gases (GHGs) and other harmful pollutants from the electricity generation sector. Consequently, green roofs and solar panels have both become increasingly popular worldwide, and...
Show moreGreen roofs and roof-mounted solar PV arrays have a wide range of environmental and economic benefits, including significantly longer roof lifetimes, reductions in urban runoff, mitigation of the urban heat island (UHI) effect, reduced electricity demand and energy dependence, and/or reduced emissions of greenhouse gases (GHGs) and other harmful pollutants from the electricity generation sector. Consequently, green roofs and solar panels have both become increasingly popular worldwide, and promising new research has emerged for their potential combination in Green Roof Integrated Photovoltaic (GRIPV) roofing applications. However, due to policy resistance, these alternatives still have marginal market shares in the U.S., while GRIPV research and development is still severely limited today. As a result, these options are not yet sufficiently widespread in the United States as to realize their full potential, particularly due to a variety of policy resistance effects with respect to each specific alternative. The steps in the System Dynamics (SD) methodology to be used in this study are summarized as follows. First, based on a comprehensive review of relevant literature, a causal loop diagram (CLD) will be drawn to provide a conceptual illustration of the modeled system. Second, based on the feedback relationships observed in this CLD, a stock-flow diagram (SFD) will be developed to form a quantitative model. Third, the modeled SFD will be tested thoroughly to ensure its structural and behavioral validity with respect to the modeled system in reality using whatever real world data is available. Fourth, different policy scenarios will be simulated within the model to evaluate their long-term effectiveness. Fifth, uncertainty analyses will be performed to evaluate the inherent uncertainties associated with the analyses in this study. Finally, the results observed for the analyses in this study and possible future research steps will be discussed and compared as appropriate.
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Date Issued: 2018
Identifier: CFE0007406, ucf:52741
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007406

Title: Scalable Map Information Dissemination for Connected and Automated Vehicle Systems.
Creator: Gani, S M Osman, Pourmohammadi Fallah, Yaser, Vosoughi, Azadeh, Yuksel, Murat, Chatterjee, Mainak, Hasan, Samiul, University of Central Florida
Abstract / Description: Situational awareness in connected and automated vehicle (CAV) systems becomes particularly challenging in the presence of non-line of sight objects and/or objects beyond the sensing range of local onboard sensors. Despite the fact that fully autonomous driving requires the use of multiple redundant sensor systems, primarily including camera, radar, and LiDAR, the non-line of sight object detection problem still persists due to the inherent limitations of those sensing techniques. To tackle...
Show moreSituational awareness in connected and automated vehicle (CAV) systems becomes particularly challenging in the presence of non-line of sight objects and/or objects beyond the sensing range of local onboard sensors. Despite the fact that fully autonomous driving requires the use of multiple redundant sensor systems, primarily including camera, radar, and LiDAR, the non-line of sight object detection problem still persists due to the inherent limitations of those sensing techniques. To tackle this challenge, the inter-vehicle communication system is envisioned that allows vehicles to exchange self-status updates aiming to extend their effective field of view and thus compensate for the limitations of the vehicle tracking subsystem that relies substantially on onboard sensing devices. Tracking capability in such systems can be further improved through the cooperative sharing of locally created map data instead of transmitting only self-update messages containing core basic safety message (BSM) data. In the cooperative sharing of safety messages, it is imperative to have a scalable communication protocol to ensure optimal use of the communication channel. This dissertation contributes to the analysis of the scalability issue in vehicle-to-everything (V2X) communication and then addresses the range issue of situational awareness in CAV systems by proposing a content-adaptive V2X communication architecture. To that end, we first analyze the BSM scheduling protocol standardized in the SAE J2945/1 and present large-scale scalability results obtained from a high-fidelity simulation platform to demonstrate the protocol's efficacy to address the scalability issues in V2X communication. By employing a distributed opportunistic approach, the SAE J2945/1 congestion control algorithm keeps the overall offered channel load within an optimal operating range, while meeting the minimum tracking requirements set forth by upper-layer applications. This scheduling protocol allows event-triggered and vehicle-dynamics driven message transmits that further the situational awareness in a cooperative V2X context. Presented validation results of the congestion control algorithm include position tracking errors as the performance measure, with the age of communicated information as the evaluation measure. In addition, we examine the optimality of the default settings of the congestion control parameters. Comprehensive analysis and trade-off study of the control parameters reveal some areas of improvement to further the algorithm's efficacy. Motivated by the effectiveness of channel congestion control mechanism, we further investigate message content and length adaptations, together with transmit rate control. Reasonably, the content of the exchanged information has a significant impact on the map accuracy in cooperative driving systems. We investigate different content control schemes for a communication architecture aimed at map sharing and evaluate their performance in terms of position tracking error. This dissertation determines that message content should be concentrated to mapped objects that are located farther away from the sender to the edge of the local sensor range. This dissertation also finds that optimized combination of message length and transmit rate ensures the optimal channel utilization for cooperative vehicular communication, which in turn improves the situational awareness of the whole system.
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Date Issued: 2019
Identifier: CFE0007634, ucf:52470
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007634

Title: Fluid Flow Characteristics of a Co-Flow Fluidic Slot Jet Thrust Augmentation Propulsion System.
Creator: Garrett, Brian, Ahmed, Kareem, Kapat, Jayanta, Bhattacharya, Samik, University of Central Florida
Abstract / Description: The UAV industry is booming with investments in research and development on improving UAV systems in order to increase applications and reduce costs of the use of these machines. Current UAV machines are developed according to the quadcopter design which has a rotary propulsion system which provides the lift needed for the aerial vehicles. This design has some flaws; namely safety concerns and noise/vibration production both of which come from the rotary propulsion system. As such, a novel...
Show moreThe UAV industry is booming with investments in research and development on improving UAV systems in order to increase applications and reduce costs of the use of these machines. Current UAV machines are developed according to the quadcopter design which has a rotary propulsion system which provides the lift needed for the aerial vehicles. This design has some flaws; namely safety concerns and noise/vibration production both of which come from the rotary propulsion system. As such, a novel propulsion system using slip stream air passed through high performance slot jets is proposed and analysis of the fluid characteristics is presented in this report.The test section for the experiment is developed using 3D printed ABS plastic airfoils modified with internal cavities where pressurized air is introduced and then expelled through slot jets on the pressure side of the airfoils. Entrainment processes develop in the system through high momentum fluid introduction into a sedentary secondary fluid. Entrainment is governed by pressure gradients and turbulent mixing and so turbulent quantities that measure these processes are extracted and analyzed according to the independent variable's effects on these quantities. Pitot probe testing extracted one dimensional fluid information and PIV analysis is used to characterize the two-dimensional flow aspects.High slot jet velocities are seen to develop flows dominated by convection pushing momentum mixing downstream reducing the mixing while low slot jet speeds exhibit higher mass fluxes and thrust development. Confinement spacing is seen to cause a decrease in flow velocity and thrust as the spacing is decreased for high speed runs. The most constricted cross sectional runs showed high momentum mixing and developed combined self-similar flow through higher boundary layer interactions and pressures, but this also hurt thrust development. The Angle of Attack of the assembly proved to be the most important variable. Outward angling showed the influence of coanda effects but also demonstrated the highest bulk fluid flow with turbulence driven momentum mixing. Inward angling created combined fluid flow downstream with high momentum mixing upstream driven by pressure. Minimal mixing is seen when the airfoils are not angled and high recirculation zones along the boundaries. The optimal setup is seen to when the airfoils are angled outwards where the highest thrust and bulk fluid movement is developed driven by the turbulent mixing induced by the increasing cross sectional area of the system.
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Date Issued: 2019
Identifier: CFE0007636, ucf:52509
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007636

Title: FILM COOLING WITH WAKE PASSING APPLIED TO AN ANNULAR ENDWALL.
Creator: Tran, Nghia, Kapat, Jayanta, University of Central Florida
Abstract / Description: Advancement in turbine technology has far reaching effects on today's society and environment. With more than 90% of electricity and 100% of commercial air transport being produced by the usage of gas turbine, any advancement in turbine technology can have an impact on fuel used, pollutants and carbon dioxide emitted to the environment. Within the turbine engine, fully understanding film cooling is critical to reliability of a turbine engine. Film cooling is an efficient way to protect...
Show moreAdvancement in turbine technology has far reaching effects on today's society and environment. With more than 90% of electricity and 100% of commercial air transport being produced by the usage of gas turbine, any advancement in turbine technology can have an impact on fuel used, pollutants and carbon dioxide emitted to the environment. Within the turbine engine, fully understanding film cooling is critical to reliability of a turbine engine. Film cooling is an efficient way to protect the engine surface from the extremely hot incoming gas, which is at a temperature much higher than allowable temperature of even the most advanced super alloy used in turbine. Film cooling performance is affected by many factors: geometrical factors and as well as flow conditions. In most of the film cooling literature, film effectiveness has been used as criterion to judge and/or compare between film cooling designs. Film uniformity is also a critical factor, since it determines how well the coolant spread out downstream to protect the hot-gas-path surface of a gas turbine engine. Even after consideration of all geometrical factors and flow conditions, the film effectiveness is still affected by the stator-rotor interaction, in particular by the moving wakes produced by upstream airfoils. A complete analysis of end wall film cooling inside turbine is required to fully understand the phenomena. This full analysis is almost impossible in the academic arena. Therefore, a simplified but critical experimental rig and computational fluid model were designed to capture the effect of wake on film cooling inside an annular test section. The moving wakes are created by rotating a wheel with 12 spokes or rods with a variable speed motor. Thus changing the motor speed will alter the wake passing frequency. This design is an advancement over most previous studies in rectangular duct, which cannot simulate wakes in an annular passage as in an engine. This rig also includes film injection that allows study of impact of moving wakes on film cooling. This wake is a simplified representation of the trailing edge created by an upstream airfoil. An annulus with 30Ã‚Â° pitch test section is considered in this study. This experimental rig is based on an existing flat plate film cooling (BFC) rig that has been validated in the past. Measurement of velocity profiles within the moving wake downstream from the wake generator is used to validate the CFD rotating wake model. The open literature on film cooling and past experiments performed in the laboratory validated the CFD film cooling model. With these validations completed, the full CFD model predicts the wake and film cooling interaction. Nine CFD cases were considered by varying the film cooling blowing ratio and the wake Strouhal number. The results indicated that wakes highly enhance film cooling effectiveness near film cooling holes and degrades the film blanket downstream of the film injection, at the moment of wake passing. However, the time-averaged film cooling effectiveness is more or less the same with or without wake.
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Date Issued: 2010
Identifier: CFE0003483, ucf:48956
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003483

Radiation (4)	+ -
side effects (4)	+ -
teacher effectiveness (4)	+ -
Florida (3)	+ -
Game-Based Training (3)	+ -

LDMOS (3)	+ -
Learning (3)	+ -
Teacher Effectiveness (3)	+ -
effectiveness (3)	+ -
media effects (3)	+ -
Adiabatic Film Cooling Effectiveness (2)	+ -
Au (2)	+ -
Cognitive Load Theory (2)	+ -
Cu (2)	+ -
Diffusion (2)	+ -
Empirical Bayes (2)	+ -
Experimental (2)	+ -
Feedback (2)	+ -
Film Cooling (2)	+ -
Florida Comprehensive Assessment Test (2)	+ -
Flow (2)	+ -
Graphene (2)	+ -
Highway Safety Manual (2)	+ -
Kondo effect (2)	+ -
Modality Effect (2)	+ -
Physiological effect (2)	+ -
Pt (2)	+ -
RF circuit performance (2)	+ -
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ETD Collection (150)	+ -
Honors Collection (19)	+ -
PRISM: Political & Rights Issues & Social Movements (2)	+ -

University of Central Florida (164)	+ -
Murray, Barbara (9)	+ -
Abdel-Aty, Mohamed (7)	+ -
Murray, Kenneth (7)	+ -
Doherty, Walter (6)	+ -

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