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Title: Recollections: An Internal Analysis of Memory and Perception.
Creator: Jimenez, Samuel, Kovach, Keith, Price, Mark, Raimundi-Ortiz, Wanda, Poindexter, Carla, University of Central Florida
Abstract / Description: I investigate the depths of memory, the entanglement of personal recollections withcommunal knowledge (learned semantic information from media and society such as facts and social norms) and the changing perceptions of environments over time. Memories define us. Throughout life we are exposed to vast quantities of imagery through a variety of media and personal experiences. Over time our firsthand experiences and what we witness in film, print, photography, and the internet become...
Show moreI investigate the depths of memory, the entanglement of personal recollections withcommunal knowledge (learned semantic information from media and society such as facts and social norms) and the changing perceptions of environments over time. Memories define us. Throughout life we are exposed to vast quantities of imagery through a variety of media and personal experiences. Over time our firsthand experiences and what we witness in film, print, photography, and the internet become indistinguishable in our memory.My work recreates consequential scenes from my past through technical drawings and blended imagery while exploring the possibilities provided by the interaction of common knowledge and the ambiguous nature of memory.
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Date Issued: 2014
Identifier: CFE0005188, ucf:50623
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005188

Title: STRUCTURAL CAUSES OF SOCIAL CONFLICT IN AFRICA.
Creator: Charland, Lucien, Dolan, Thomas, University of Central Florida
Abstract / Description: Social conflict, as opposed to armed conflict, has received less attention in the field of quantitative research. This paper investigates the structural causes of political violence in 35 African states using data from the Social Conflict in Africa dataset and the Beck and Katz panel corrected standard errors time series regression model. Theoretically, a closed political opportunity structure, combined with a weak state unable to provide public goods, should together produce high levels of...
Show moreSocial conflict, as opposed to armed conflict, has received less attention in the field of quantitative research. This paper investigates the structural causes of political violence in 35 African states using data from the Social Conflict in Africa dataset and the Beck and Katz panel corrected standard errors time series regression model. Theoretically, a closed political opportunity structure, combined with a weak state unable to provide public goods, should together produce high levels of social conflict. The independent variables attempt to operationalize these concepts from four different angles. In this analysis Access to Education and Infrastructure (AEI), Ethno Linguistic Fractionalization (ELF), Freedom in the World Political Rights (FIW), and National Material Capabilities (NMC) were all significant predictors of social conflict. This study found that as the level of ethnic fractionalization and material capabilities within states rose, the frequency of social conflict events also increased. However, as access to infrastructure and political rights declined, the number of social conflict events increased. Wald chi-square and R-square values suggest that the model is complete and has substantial explanatory power.
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Date Issued: 2014
Identifier: CFH0004663, ucf:45314
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004663

Title: NEW DEVELOPMENTS ON HIGH-RESOLUTION LUMINESCENCE SPECTROSCOPY AND THEIR APPLICATION TO THE DIRECT ANALYSIS OF ORGANIC POLLUTANTS IN ENVIRONMENTAL SAMPLES.
Creator: yu, shenjiang, Campiglia, Andres, University of Central Florida
Abstract / Description: Polycyclic aromatic compounds (PACs), which comprise a complex class of condensed multi-ring benzenoid compounds, are important environmental pollutants originating from a wide variety of natural and anthropogenic sources. PACs are generally formed during incomplete combustion of pyrolisis of organic matter containing carbon and hydrogen. Because combustion of organic materials is involved in countless natural processes or human activities, PACs are omnipresent and abundant pollutants in air,...
Show morePolycyclic aromatic compounds (PACs), which comprise a complex class of condensed multi-ring benzenoid compounds, are important environmental pollutants originating from a wide variety of natural and anthropogenic sources. PACs are generally formed during incomplete combustion of pyrolisis of organic matter containing carbon and hydrogen. Because combustion of organic materials is involved in countless natural processes or human activities, PACs are omnipresent and abundant pollutants in air, soil, and water. Chemical analysis of PACs is of great environmental and toxicological importance. Many of them are highly suspect as etiological agents in human cancer. Because PACs carcinogenic properties strongly depend on molecular structure and differ significantly from isomer to isomer, it is of paramount importance to determine the most toxic isomers even if they are present at much lower concentrations than their less toxic isomers. Gas chromatography (GC), high-resolution GC, and high-performance liquid chromatography (HPLC) are the basis for standard PACs identification and determination. Many cases exist where GC, HPLC, and even HR-GC have not been capable to provide unambiguous isomer identification. The lack of reliable analytical data has lead to serious errors in environmental and toxicological studies. This dissertation deals with the development of novel instrumentation and analytical methods for the analysis of PACs in environmental samples. The developed methodology is based on two well-known high-resolution luminescence techniques, namely Shpol'skii Spectroscopy (SS) and Fluorescence Line Narrowing Spectroscopy (FLNS). Although these two techniques have long been recognized for their capability in providing direct determination of target PACs in complex environmental samples, several reasons have hampered their widespread use for the problem at hand. These include inconvenient sample freezing procedures; questions about signal reproducibility; lengthy spectral acquisition, which might cause severe sample degradation due to prolonged excitation; broadband fluorescence background that degrades quality of spectra, precision of measurements and detection limits; solvent constrains imposed by the need of optically transparent media; and, most importantly, the lack of selectivity and sensitivity for unambiguous determination of closely related PACs metabolites. This dissertation presents significant advances on all fronts. The analytical methodology is then extended to the analysis of fluoroquinolones (FQs) in aqueous samples. FQs are one of the most powerful classes of antibiotics currently used for the treatment of urinary tract infections. Their widespread use in both human and animal medicine has prompted their appearance in aquatic systems. The search for a universal method capable to face this new environmental challenge has been centered on HPLC. Depending on the FQ and its concentration level, successful determination has been accomplished with mass spectrometry, room-temperature fluorescence (RTF) or UV absorption spectrometry. Unfortunately, no single detection mode has shown the ability to detect all FQ at the concentration ratios found in environmental waters. We provide a feasible alternative based on FLNS. On the instrumentation side, we present a single instrument with the capability to collect multidimensional data formats in both the fluorescence and the phosphorescence time domains. We demonstrate the ability to perform luminescence measurements in highly scattering media by comparing the precision of measurements in optically transparent solvents (Shpol'skii solvents) to those obtained in "snow-like" matrixes and solid samples. For decades, conventional low-temperature methodology has been restricted to optically transparent media. This restriction has limited its application to organic solvents that freeze into a glass. In this dissertation, we remove this limitation with the use of cryogenic fiber-optic probes. Our final efforts deal with low-temperature absorption measurements. Recording absorption spectra via transmittance through frozen matrixes is a challenging task. The main reason is the difficulty to overcome the strong scattering light reaching the detector. This is particularly true when thick samples are necessary for recording absorption spectra of weak oscillators. In the case of strongly fluorescent compounds, additional errors in absorbance measurements arise from the emission reaching the detector, which might have comparable intensity to that of the transmitted light. We present a fundamentally different approach to low-temperature absorption measurements as the sought-for-information is the intensity of laser excitation returning from the frozen sample to the intensified-charge coupled device (ICCD). Laser excitation is collected with the aid of a cryogenic fiber optic probe. The feasibility of our approach is demonstrated with single-site and multiple-site Shpol'skii systems. 4.2K absorption spectra show excellent agreement to their literature counterparts recorded via transmittance with closed cycle cryogenators. Fluorescence quantum yields measured at room-temperature compare well to experimental data acquired in our lab via classical methodology. Similar agreement is observed between 77K fluorescence quantum yields and previously reported data acquired with classical methodology. We then extend our approach to generate original data on fluorescence quantum yields at 4.2K.
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Date Issued: 2006
Identifier: CFE0001456, ucf:47039
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001456

Title: METHANE AND DIMETHYL ETHER OXIDATION AT ELEVATED TEMPERATURES AND PRESSURE.
Creator: Zinner, Christopher, Basu, Saptarshi, University of Central Florida
Abstract / Description: Autoignition and oxidation of two Methane (CH4) and Dimethyl Ether (CH3OCH3 or DME) mixtures in air were studied in shock tubes over a wide range of equivalence ratios at elevated temperatures and pressures. These experiments were conducted in the reflected shock region with pressures ranging from 0.8 to 35.7 atmospheres, temperatures ranging from 913 to 1650 K, and equivalence ratios of 2.0, 1.0, 0.5, and 0.3. Ignition delay times were obtained from shock-tube endwall pressure traces for...
Show moreAutoignition and oxidation of two Methane (CH4) and Dimethyl Ether (CH3OCH3 or DME) mixtures in air were studied in shock tubes over a wide range of equivalence ratios at elevated temperatures and pressures. These experiments were conducted in the reflected shock region with pressures ranging from 0.8 to 35.7 atmospheres, temperatures ranging from 913 to 1650 K, and equivalence ratios of 2.0, 1.0, 0.5, and 0.3. Ignition delay times were obtained from shock-tube endwall pressure traces for fuel mixtures of CH4/CH3OCH3 in ratios of 80/20 percent volume and 60/40 percent volume, respectively. Close examination of the data revealed that energy release from the mixture is occurring in the time between the arrival of the incident shock wave and the ignition event. An adjustment scheme for temperature and pressure was devised to account for this energy release and its effect on the ignition of the mixture. Two separate ignition delay correlations were developed for these pressure- and temperature-adjusted data. These correlations estimate ignition delay from known temperature, pressure, and species mole fractions of methane, dimethyl ether, and air (0.21 O2 + 0.79 N2). The first correlation was developed for ignition delay occurring at temperatures greater than or equal to 1175 K and pressures ranging from 0.8 to 35.3 atm. The second correlation was developed for ignition delay occurring at temperatures less than or equal to 1175 K and pressures ranging from 18.5 to 40.0 atm. Overall good agreement was found to exist between the two correlations and the data of these experiments. Findings of these experiments also include that with pressures at or below ten atm, increased concentrations of dimethyl ether will consistently produce faster ignition times. At pressures greater than ten atmospheres it is possible for fuel rich mixtures with lower concentrations of dimethyl ether to give the fastest ignition times. This work represents the most thorough shock tube investigation for oxidation of methane with high concentration levels of dimethyl ether at gas turbine engine relevant temperatures and pressures. The findings of this study should serve as a validation for detailed chemical kinetics mechanisms.
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Date Issued: 2008
Identifier: CFE0002096, ucf:47539
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002096

Title: PHYSICAL CHARACTERISTICS OF AN INDIVIDUAL: THE IDENTIFICATION OF BIOMARKERS FOR BIOLOGICAL AGE DETERMINATION.
Creator: Alvarez, Michelle, Ballantyne, Jack, University of Central Florida
Abstract / Description: It is now a matter of routine for the forensic scientist to obtain the genetic profile of an individual from DNA recovered from a biological stain deposited at a crime scene. Potential contributors of the stain must either be known to investigators (i.e. a developed suspect) or the questioned profile must be searched against a database of DNA profiles such as those maintained in the CODIS National DNA database. However, in those instances where there is no developed suspect and no match is...
Show moreIt is now a matter of routine for the forensic scientist to obtain the genetic profile of an individual from DNA recovered from a biological stain deposited at a crime scene. Potential contributors of the stain must either be known to investigators (i.e. a developed suspect) or the questioned profile must be searched against a database of DNA profiles such as those maintained in the CODIS National DNA database. However, in those instances where there is no developed suspect and no match is obtained after interrogation of appropriate DNA databases, the DNA profile per se presently provides no meaningful information to investigators, with the notable exception of gender determination. In these situations it would be advantageous to the investigation, if additional probative information could be obtained from the biological stain. A useful biometric that could provide important probative information, and one that may be amenable to molecular genetic analysis, is the biological age of an individual. The ability to provide investigators with information as to whether a DNA donor is a newborn, infant, toddler, child, adolescent, adult, middle-aged or elderly individual could be useful in certain cases, particularly those involving young children such as kidnappings or in providing additional intelligence during terrorist investigations. Currently no validated molecular assays exist for age determination. Biological human ageing can be defined by two distinct processes, degenerative and developmental ageing. The degenerative process of ageing is based on theories which identify an increase or decrease in physiological conditions with increasing age. In contrast, the developmental process of ageing is based on the theory that as individuals increase in chronological age, there will be subtle corresponding molecular based biological changes, each requiring genes to be expressed or silenced, indicative of that particular stage of life. We investigated the degenerative process of chromosomal telomere shortening, as well as the developmental process of gene expression profiling analysis, in an attempt to identify biomarkers of biological age in a self-renewing tissue such as blood. While telomere length analysis was an ineffective method for age determination; gene expression analysis revealed three gene transcripts expressed in an age-dependent physiological manner. These species namely- COL1A2, HBE1 and IGFBP3, were found to be expressed at elevated levels in younger individuals, newborns, or post-pubertal individuals, respectively. The biological process of hemoglobin switching was also investigated for the possibility of determining human age. While experimenting with the potential of using the gamma-hemoglobin chains, as newborn specific gene candidates, we serendipitously discovered four novel truncated transcripts, which we have termed HBG1n1, HBG1n2, HBG2n2 and HBG2n3; whose expression was restricted to whole-blood newborn samples and specific fetal tissues. The molecular origin of these transcripts appears to be at the RNA level, being produced by specific rearrangement events occurring in the standard gamma hemoglobin transcripts (HBG1 and HBG2), which yield these new isoforms that are expressed in a highly regulated tissue specific manner.
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Date Issued: 2007
Identifier: CFE0001737, ucf:47297
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001737

Title: MAC LAYER AND ROUTING PROTOCOLS FOR WIRELESS AD HOC NETWORKS WITH ASYMMETRIC LINKS AND PERFORMANCE EVALUATION STUDIES.
Creator: Wang, Guoqiang, Marinescu, Dan, University of Central Florida
Abstract / Description: In a heterogeneous mobile ad hoc network (MANET), assorted devices with different computation and communication capabilities co-exist. In this thesis, we consider the case when the nodes of a MANET have various degrees of mobility and range, and the communication links are asymmetric. Many routing protocols for ad hoc networks routinely assume that all communication links are symmetric, if node A can hear node B and node B can also hear node A. Most current MAC layer protocols are unable to...
Show moreIn a heterogeneous mobile ad hoc network (MANET), assorted devices with different computation and communication capabilities co-exist. In this thesis, we consider the case when the nodes of a MANET have various degrees of mobility and range, and the communication links are asymmetric. Many routing protocols for ad hoc networks routinely assume that all communication links are symmetric, if node A can hear node B and node B can also hear node A. Most current MAC layer protocols are unable to exploit the asymmetric links present in a network, thus leading to an inefficient overall bandwidth utilization, or, in the worst case, to lack of connectivity. To exploit the asymmetric links, the protocols must deal with the asymmetry of the path from a source node to a destination node which affects either the delivery of the original packets, or the paths taken by acknowledgments, or both. Furthermore, the problem of hidden nodes requires a more careful analysis in the case of asymmetric links. MAC layer and routing protocols for ad hoc networks with asymmetric links require a rigorous performance analysis. Analytical models are usually unable to provide even approximate solutions to questions such as end-to-end delay, packet loss ratio, throughput, etc. Traditional simulation techniques for large-scale wireless networks require vast amounts of storage and computing cycles rarely available on single computing systems. In our search for an effective solution to study the performance of wireless networks we investigate the time-parallel simulation. Time-parallel simulation has received significant attention in the past. The advantages, as well as, the theoretical and practical limitations of time-parallel simulation have been extensively researched for many applications when the complexity of the models involved severely limits the applicability of analytical studies and is unfeasible with traditional simulation techniques. Our goal is to study the behavior of large systems consisting of possibly thousands of nodes over extended periods of time and obtain results efficiently, and time-parallel simulation enables us to achieve this objective. We conclude that MAC layer and routing protocols capable of using asymmetric links are more complex than traditional ones, but can improve the connectivity, and provide better performance. We are confident that approximate results for various performance metrics of wireless networks obtained using time-parallel simulation are sufficiently accurate and able to provide the necessary insight into the inner workings of the protocols.
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Date Issued: 2007
Identifier: CFE0001736, ucf:47302
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001736

Title: WALL HEAT TRANSFER EFFECTS IN THE ENDWALL REGION BEHIND A REFLECTED SHOCK WAVE AT LONG TEST TIMES.
Creator: Frazier, Corey, Petersen, Eric, University of Central Florida
Abstract / Description: Shock-tube experiments are typically performed at high temperatures (>1200K) due to test-time constraints. These test times are usually ~1 ms in duration and the source of this short, test-time constraint is loss of temperature due to heat transfer. At short test times, there is very little appreciable heat transfer between the hot gas and the cold walls of the shock tube and a high test temperature can be maintained. However, some experiments are using lower temperatures (approx. 800K) to...
Show moreShock-tube experiments are typically performed at high temperatures (>1200K) due to test-time constraints. These test times are usually ~1 ms in duration and the source of this short, test-time constraint is loss of temperature due to heat transfer. At short test times, there is very little appreciable heat transfer between the hot gas and the cold walls of the shock tube and a high test temperature can be maintained. However, some experiments are using lower temperatures (approx. 800K) to achieve ignition and require much longer test times (up to 15 ms) to fully study the chemical kinetics and combustion chemistry of a reaction in a shock-tube experiment. Using mathematical models, analysis was performed studying the effects of temperature, pressure, shock-tube inner diameter, and test-port location at various test times (from 1 – 20 ms) on temperature maintenance. Three models, each more complex than the previous, were used to simulate test conditions in the endwall region behind the reflected shock wave with Ar and N2 as bath gases. Temperature profile, thermal BL thickness, and other parametric results are presented herein. It was observed that higher temperatures and lower pressures contributed to a thicker thermal boundary layer, as did shrinking inner diameter. Thus it was found that a test case such as 800K and 50 atm in a 16.2-cm-diameter shock tube in Argon maintained thermal integrity much better than other cases – pronounced by a thermal boundary layer < 1 mm thick and an average temperature > 799.9 K from 1–20 ms.
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Date Issued: 2007
Identifier: CFE0001593, ucf:47162
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001593

Title: A DEVIANCE REGULATION THEORY INTERVENTION TO REDUCE ALCOHOL PROBLEMS AMONG FIRST-YEAR COLLEGE STUDENTS.
Creator: Leary, Angelina V, Dvorak, Robert, University of Central Florida
Abstract / Description: OBJECTIVE: An alcohol-drinking culture exists among first-time-in-college students, where many of these students come to their university relatively inexperienced with alcohol, which may increase alcohol-related consequences. Several interventions exist to combat this campus problem. The current study investigates the use of a Deviance Regulation Theory (DRT) intervention, presented in a web-based manner, to increase alcohol Protective Behavioral Strategies (PBS), such as monitoring drinks,...
Show moreOBJECTIVE: An alcohol-drinking culture exists among first-time-in-college students, where many of these students come to their university relatively inexperienced with alcohol, which may increase alcohol-related consequences. Several interventions exist to combat this campus problem. The current study investigates the use of a Deviance Regulation Theory (DRT) intervention, presented in a web-based manner, to increase alcohol Protective Behavioral Strategies (PBS), such as monitoring drinks, using a designated driver, and drinking water in between alcoholic beverages, among college freshmen. METHOD: College freshmen participants (N = 157) completed web-based surveys examining alcohol behaviors once a week for six weeks. Participants were randomly assigned to one of three conditions: a positive frame about individuals who used PBS, a negative frame about individuals who did not use PBS, or a control group that did not receive a DRT intervention. Participants also reported their perception of PBS use among UCF students and friend. Data was analyzed in each PBS subtype: Manner of Drinking, Stop/Limiting Drinking, and Serious Harm Reduction. RESULTS AND CONCLUSION: Results indicate a negatively framed message with high perceived norm levels results in increased PBS use, which may suggest college freshmen have a strong drive to "fit in", or avoid standing out in negative ways. Further, there seems to be little desire to standout in positive ways among first-year students. This may be indicative of individuals who modify their behavior in order to assimilate to a new and unfamiliar environment. Furthermore, some PBS strategies were associated with decreases in alcohol consumption and alcohol-related problems. Results suggest a DRT intervention may be beneficial to first-time-in-college students.
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Date Issued: 2018
Identifier: CFH2000427, ucf:45715
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000427

Title: COMPARISON OF ACOUSTIC MEASURES IN DISCRIMINATING BETWEEN THOSE WITH FRIEDREICH'S ATAXIA AND NEUROLOGICALLY NORMAL PEERS.
Creator: Luna-Webb, Sophia, Carson, Cecyle, University of Central Florida
Abstract / Description: Background: Technological advancements in speech acoustic analysis have led to the development of spectral/cepstral analyses due to questions regarding the validity of traditional time-based measures (i.e., Jitter, Shimmer, and Harmonics-to-Noise-Ratio) in objectifying perturbations in dysphonic voices. Aim: This study investigated the validity of time-based measures in discriminating those with Friedreich's ataxia (FA) from normal voiced (NV) peers when compared to cepstral-spectral measures...
Show moreBackground: Technological advancements in speech acoustic analysis have led to the development of spectral/cepstral analyses due to questions regarding the validity of traditional time-based measures (i.e., Jitter, Shimmer, and Harmonics-to-Noise-Ratio) in objectifying perturbations in dysphonic voices. Aim: This study investigated the validity of time-based measures in discriminating those with Friedreich's ataxia (FA) from normal voiced (NV) peers when compared to cepstral-spectral measures. Method: A total of 120 sustained vowel phonations from an existing database of 40 participants (20 FA; 20 NV) of the vowels /Q/, /i/, and /o/ were analyzed to determine which set of variables (i.e., time-based vs. cepstral-spectral) better predicted group membership. Four variables of time-based measures (Jitter Local %, Jitter RAP, Shimmer Local %, Shimmer APQ11, and HNR) were analyzed via the freeware program PRAAT and compared to four cepstral-spectral measures (Cepstral Peak Prominence, Cepstral Peak Prominence Standard Deviation, Low/High Ratio Standard Deviation, and the Cepstral/ Spectral Index of Dysphonia) extracted from the Analysis of Dysphonia in Speech and Voice (ADSV) software program. Results: Findings from a discriminant analysis showed sensitivity and specificity results to be better for ADSV measures; 100% of those in the FA group were classified correctly (sensitivity), and 95% of members in the NV group were correctly identified (specificity) as compared to PRAAT (70% sensitivity and 85% specificity). Conclusions: Cepstral-spectral measures are much more accurate in discriminating between those with FA and NV peers as compared to time-based estimates.
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Date Issued: 2015
Identifier: CFH0004824, ucf:45463
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004824

Title: PREDICTING THE PERFORMANCE OF INTERPRETING INSTRUCTION BASED ON DIGITAL PROPENSITY INDEX SCORE IN TEXT AND GRAPHIC FORMATS.
Creator: Norman, David, Hirumi, Atsusi, University of Central Florida
Abstract / Description: Practitioners have proposed that Digital Natives prefer graphics while Digital Immigrants prefer text. While Instructional Design has been extensively studied and researched, the impact of the graphical emphasis in instructional designs as it relates to digital propensity has not been widely explored. Specifically, this study examined the performance of students when presented with text-only and graphic-only instructional formats. The purpose of this study was to test the relationship between...
Show morePractitioners have proposed that Digital Natives prefer graphics while Digital Immigrants prefer text. While Instructional Design has been extensively studied and researched, the impact of the graphical emphasis in instructional designs as it relates to digital propensity has not been widely explored. Specifically, this study examined the performance of students when presented with text-only and graphic-only instructional formats. The purpose of this study was to test the relationship between Digital Propensity Index scores of individuals and their performance when interpreting online instruction. A sample of students from the population of a large metropolitan university received the Digital Propensity Index questionnaire, which is a measure of an individual's time spent interacting with digital media. Each student was randomly assigned varying formats of a computer-based instructional unit via a public survey. The instructional unit consisted of the DPI questionnaire and six tasks related to the Central Florida commuter rail system. Participants were asked to answer the DPI questionnaire on a website by clicking on a link in an emailed invitation. Following the DPI questionnaire, participants were randomly assigned to one of two groups. Group One saw three instructional tasks shown in text and shuffled in random order. Each task was displayed on its own webpage. By submitting an answer to the task, the group progressed through the website to the next task. Group Two saw graphic tasks first, again, shuffled in random order. After the first three tasks, the groups swapped instructional formats to view the opposing group's initial questions. Participants were timed on how many seconds they spent reviewing each task. Each task had an assessment question to evaluate the learning outcomes of the instructional unit. Finally, the DPI score of the participant was matched with the time spent viewing each presentation format. The findings indicate that DPI score had a statistically significant prediction of time spent navigating each type of instruction. Though the link between DPI score and time spent navigating instruction was statistically significant, the actual measurable time difference between navigating text and graphic formats was only a fraction of a second for each increment in DPI score. Limitations and potential future research related to the study are discussed as well.
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Date Issued: 2008
Identifier: CFE0002234, ucf:47896
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002234

Title: A COMPARATIVE ANALYSIS OF DIFFERENCES IN RESIDENT SATISFACTION, RETENTION, AND CUMULATIVE GRADE POINT AVERAGE BETWEEN UNIVERSITY OF CENTRAL FLORIDA OWNED AND AFFILIATED HOUSING.
Creator: Novak, Jeffrey, Taylor, Rosemarye, University of Central Florida
Abstract / Description: This study compared students' perceptions and satisfaction as they related to their place of residence. In addition, this study sought to determine if a difference existed between student retention rates from their first year in college to their second year and one's grade point average with respect to one's place of residence within the collegiate setting. As such, the problem this study examined was the overall impact of where a first-time-in-college student lived within the...
Show moreThis study compared students' perceptions and satisfaction as they related to their place of residence. In addition, this study sought to determine if a difference existed between student retention rates from their first year in college to their second year and one's grade point average with respect to one's place of residence within the collegiate setting. As such, the problem this study examined was the overall impact of where a first-time-in-college student lived within the University of Central Florida housing system and how that living environment impacted students' levels of satisfaction, overall retention rates, and cumulative grade point averages. The data used for this study were obtained from a previously distributed survey conducted by the Department of Housing and Residence Life at the University of Central Florida in February 2007. Secondary data were obtained through the Department of Institutional Research at the University of Central Florida. A website link to an optional, self-administered Internet-based survey was sent via email to University of Central Florida students residing in university owned housing and university affiliated housing. The size of the sample was determined by the number of delivered emails 3800 for university owned housing, 1,500 for university affiliated housing (Towers), and 1,831 for university affiliated housing (Pegasus Landing). Of the total populations: 1) 38.57 percent were returned for university owned housing, 2) 26.26 percent were returned for university affiliated (Towers at Golden Knights Plaza), and 3) 24.63 percent were returned for university affiliated housing (Pegasus Landing). There were many statistically significant relationships. Consistently, students residing in university owned housing showed higher satisfaction and agreement levels when compared with students living in university affiliated housing. Additionally, students living in university owned housing showed a higher retention rate and cumulative grade point average when compared with students living in university affiliated housing.
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Date Issued: 2008
Identifier: CFE0002245, ucf:47894
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002245

Title: Data-Driven Modeling and Optimization of Building Energy Consumption.
Creator: Grover, Divas, Pourmohammadi Fallah, Yaser, Vosoughi, Azadeh, Zhou, Qun, University of Central Florida
Abstract / Description: Sustainability and reducing energy consumption are targets for building operations. The installation of smart sensors and Building Automation Systems (BAS) makes it possible to study facility operations under different circumstances. These technologies generate large amounts of data. That data can be scrapped and used for the analysis. In this thesis, we focus on the process of data-driven modeling and decision making from scraping the data to simulate the building and optimizing the...
Show moreSustainability and reducing energy consumption are targets for building operations. The installation of smart sensors and Building Automation Systems (BAS) makes it possible to study facility operations under different circumstances. These technologies generate large amounts of data. That data can be scrapped and used for the analysis. In this thesis, we focus on the process of data-driven modeling and decision making from scraping the data to simulate the building and optimizing the operation. The City of Orlando has similar goals of sustainability and reduction of energy consumption so, they provided us access to their BAS for the data and study the operation of its facilities. The data scraped from the City's BAS serves can be used to develop statistical/machine learning methods for decision making. We selected a mid-size pilot building to apply these techniques. The process begins with the collection of data from BAS. An Application Programming Interface (API) is developed to login to the servers and scrape data for all data points and store it on the local machine. Then data is cleaned to analyze and model. The dataset contains various data points ranging from indoor and outdoor temperature to fan speed inside the Air Handling Unit (AHU) which are operated by Variable Frequency Drive (VFD). This whole dataset is a time series and is handled accordingly. The cleaned dataset is analyzed to find different patterns and investigate relations between different data points. The analysis helps us in choosing parameters for models that are developed in the next step. Different statistical models are developed to simulate building and equipment behavior. Finally, the models along with the data are used to optimize the building Operation with the equipment constraints to make decisions for building operation which leads to a reduction in energy consumption while maintaining temperature and pressure inside the building.
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Date Issued: 2019
Identifier: CFE0007810, ucf:52335
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007810

Title: Risk Management in Reservoir Operations in the Context of Undefined Competitive Consumption.
Creator: Salami, Yunus, Nnadi, Fidelia, Wang, Dingbao, Chopra, Manoj, Rowney, Alexander, Divo, Eduardo, University of Central Florida
Abstract / Description: Dams and reservoirs with multiple purposes require effective management to fully realize their purposes and maximize efficiency. For instance, a reservoir intended mainly for the purposes of flood control and hydropower generation may result in a system with primary objectives that conflict with each other. This is because higher hydraulic heads are required to achieve the hydropower generation objective while relatively lower reservoir levels are required to fulfill flood control objectives....
Show moreDams and reservoirs with multiple purposes require effective management to fully realize their purposes and maximize efficiency. For instance, a reservoir intended mainly for the purposes of flood control and hydropower generation may result in a system with primary objectives that conflict with each other. This is because higher hydraulic heads are required to achieve the hydropower generation objective while relatively lower reservoir levels are required to fulfill flood control objectives. Protracted imbalances between these two could increase the susceptibility of the system to risks of water shortage or flood, depending on inflow volumes and operational policy effectiveness. The magnitudes of these risks can become even more pronounced when upstream use of the river is unregulated and uncoordinated so that upstream consumptions and releases are arbitrary. As a result, safe operational practices and risk management alternatives must be structured after an improved understanding of historical and anticipated inflows, actual and speculative upstream uses, and the overall hydrology of catchments upstream of the reservoir. One of such systems with an almost yearly occurrence of floods and shortages due to both natural and anthropogenic factors is the dual reservoir system of Kainji and Jebba in Nigeria. To analyze and manage these risks, a methodology that combines a stochastic and deterministic approach was employed. Using methods outlined by Box and Jenkins (1976), autoregressive integrated moving average (ARIMA) models were developed for forecasting Niger river inflows at Kainji reservoir based on twenty-seven-year-long historical inflow data (1970-1996). These were then validated using seven-year inflow records (1997-2003). The model with the best correlation was a seasonal multiplicative ARIMA (2,1,1)x(2,1,2)12 model. Supplementary validation of this model was done with discharge rating curves developed for the inlet of the reservoir using in situ inflows and satellite altimetry data. By comparing net inflow volumes with storage deficit, flood and shortage risk factors at the reservoir were determined based on (a) actual inflows, (b) forecasted inflows (up to 2015), and (c) simulated scenarios depicting undefined competitive upstream consumption. Calculated high-risk years matched actual flood years again suggesting the reliability of the model. Monte Carlo simulations were then used to prescribe safe outflows and storage allocations in order to reduce futuristic risk factors. The theoretical safety levels achieved indicated risk factors below threshold values and showed that this methodology is a powerful tool for estimating and managing flood and shortage risks in reservoirs with undefined competitive upstream consumption.
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Date Issued: 2012
Identifier: CFE0004593, ucf:49193
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004593

Title: Characterization of composite broadband absorbing conjugated polymer nanoparticles by steady-state, time-resolved and single particle spectroscopy.
Creator: Bonner, Maxwell, Gesquiere, Andre, Campiglia, Andres, Santra, Swadeshmukul, Hernandez, Florencio, Perez Figueroa, Jesus, Ye, Jingdong, Fernandez-Valle, Cristina, University of...
Show moreBonner, Maxwell, Gesquiere, Andre, Campiglia, Andres, Santra, Swadeshmukul, Hernandez, Florencio, Perez Figueroa, Jesus, Ye, Jingdong, Fernandez-Valle, Cristina, University of Central Florida
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Abstract / Description: As the global economy searches for reliable, inexpensive and environmentally friendly renewable energy resources, energy conservation by means of photovoltaics has seen near exponential growth in the last decade. Compared to state-of-the-art inorganic solar cells, organic photovoltaics (OPVs) composed of conjugated polymers are particularly interesting because of their processability, flexibility and the potential for large area devices at a reduced fabrication cost. It has been extensively...
Show moreAs the global economy searches for reliable, inexpensive and environmentally friendly renewable energy resources, energy conservation by means of photovoltaics has seen near exponential growth in the last decade. Compared to state-of-the-art inorganic solar cells, organic photovoltaics (OPVs) composed of conjugated polymers are particularly interesting because of their processability, flexibility and the potential for large area devices at a reduced fabrication cost. It has been extensively documented that the interchain and intrachain interactions of conjugated polymers complicate the fundamental understanding of the optical and electronic properties in the solid-state (i.e. thin film active layer). These interactions are highly dependent on the nanoscale morphology of the solid-state material, leading to a heterogeneous morphology where individual conjugated polymer molecules obtain a variety of different optoelectronic properties. Therefore, it is of the utmost importance to fundamentally study conjugated polymer systems at the single molecule or nanoparticle level instead of the complex macroscopic bulk level.This dissertation research aims to develop simplified nanoparticle models that are representation of the nanodomains found in the solid-state material, while fundamentally addressing light harvesting, energy transfer and interfacial charge transfer mechanisms and their relationship to the electronic structure, material composition and morphology of the nanoparticle system. In preceding work, monofunctional doped nanoparticles (polymer-polymer) were fabricated with enhanced light harvesting and F?rster energy transfer properties by blending Poly[(o-phenylenevinylene)-alt-(2-methoxy-5-(2-ethylhexyloxy)-p-phenylenevinylene)] (BPPV) and Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) at various MEH-PPV doping ratios. While single particle spectroscopy (SPS) reveals a broad distribution of optoelectronic and photophysical properties, time-correlated single photon counting (TC-SPC) spectroscopy displays multiple fluorescence lifetime components for each nanoparticle composition, resulting from changing polymer chain morphologies and polymer-polymer aggregation. In addition, difunctional doped nanoparticles were fabricated by doping the monofunctional doped nanoparticles with PC60BM ([6,6]-phenyl-C61-butyric acid methyl ester) to investigate competition between intermolecular energy transfer and interfacial charge transfer. Specifically, the difunctional SPS data illustrated enhanced and reduced energy transfer mechanisms that are dependent on the material composition of MEH-PPV and PC60BM. These data are indicative of changes in inter- and intrachain interactions of BPPV and MEH-PPV and their respective nanoscale morphologies. Together, these fundamental studies provide a thorough understanding of monofunctional and difunctional doped nanoparticle photophysics, necessary for understanding the morphological, optoelectronic and photophysical processes that can limit the efficiency of OPVs and provide insight for strategies aimed at improving device efficiencies.
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Date Issued: 2011
Identifier: CFE0004089, ucf:49143
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004089

Title: Towards Real-time Mixed Reality Matting in Natural Scenes.
Creator: Beato, Nicholas, Hughes, Charles, Foroosh, Hassan, Tappen, Marshall, Moshell, Jack, University of Central Florida
Abstract / Description: In Mixed Reality scenarios, background replacement is a common way to immerse a user in a synthetic environment. Properly identifying the background pixels in an image or video is a difficult problem known as matting. In constant color matting, research identifies and replaces a background that is a single color, known as the chroma key color. Unfortunately, the algorithms force a controlled physical environment and favor constant, uniform lighting. More generic approaches, such as natural...
Show moreIn Mixed Reality scenarios, background replacement is a common way to immerse a user in a synthetic environment. Properly identifying the background pixels in an image or video is a difficult problem known as matting. In constant color matting, research identifies and replaces a background that is a single color, known as the chroma key color. Unfortunately, the algorithms force a controlled physical environment and favor constant, uniform lighting. More generic approaches, such as natural image matting, have made progress finding alpha matte solutions in environments with naturally occurring backgrounds. However, even for the quicker algorithms, the generation of trimaps, indicating regions of known foreground and background pixels, normally requires human interaction or offline computation. This research addresses ways to automatically solve an alpha matte for an image in real-time, and by extension video, using a consumer level GPU. It do so even in the context of noisy environments that result in less reliable constraints than found in controlled settings. To attack these challenges, we are particularly interested in automatically generating trimaps from depth buffers for dynamic scenes so that algorithms requiring more dense constraints may be used. We then explore a sub-image based approach to parallelize an existing hierarchical approach on high resolution imagery by taking advantage of local information. We show that locality can be exploited to significantly reduce the memory and compute requirements of previously necessary when computing alpha mattes of high resolution images. We achieve this using a parallelizable scheme that is both independent of the matting algorithm and image features. Combined, these research topics provide a basis for Mixed Reality scenarios using real-time natural image matting on high definition video sources.
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Date Issued: 2012
Identifier: CFE0004515, ucf:49284
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004515

Title: Laser Spark Ignition of Counter-flow Diffusion Flames: Effects of diluents and diffusive-thermal properties.
Creator: Sime Segura, Fidelio, Deng, Weiwei, Chen, Ruey-Hung, Kapat, Jayanta, University of Central Florida
Abstract / Description: A pulsed Nd:YAG laser is used to study laser spark ignition of methane counter-flow diffusion flames with the use of helium and argon as diluents to achieve a wide range of variations in transport properties. The global strain rate and Damk(&)#246;hler number on successful ignition were investigated for the effects of Lewis number and transport properties, which are dependent on the diluent type and dilution level. A high-speed camera is used to record the ignition events and a software is...
Show moreA pulsed Nd:YAG laser is used to study laser spark ignition of methane counter-flow diffusion flames with the use of helium and argon as diluents to achieve a wide range of variations in transport properties. The global strain rate and Damk(&)#246;hler number on successful ignition were investigated for the effects of Lewis number and transport properties, which are dependent on the diluent type and dilution level. A high-speed camera is used to record the ignition events and a software is used for pre-ignition flow field and mixing calculations. It is found that the role of effective Lewis number on the critical global strain rate, beyond which ignition is not possible, is qualitatively similar that on the extinction strain rate. With the same level of dilution, the inert diluent with smaller Lewis number yields larger critical global strain rate. The critical Damk(&)#246;hler number below which no ignition is possible is found to be within approximately 20% for all the fuel-inert gas mixtures studied. When successful ignition takes place, the ignition time increases as the level of dilution of argon is increased. The ignition time decreases with increasing level of helium dilution due to decreases in thermal diffusion time, which causes rapid cooling of the flammable layer during the ignition process. However, the critical strain for ignition with helium dilution rapidly decreases as the dilution level is increased. The experimental results show that with the increase of strain rate the time to steady flame decreases, and that with the increase of dilution level time for the flame to become steady increases. For the same level of dilution, the time for steady flame is observed to be longer for He-diluted flames than for Ar-diluted flames due to its thermal diffusivity being larger than that of Ar.
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Date Issued: 2012
Identifier: CFE0004295, ucf:49467
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004295

Title: Experimental Study of Sinkhole Failure Related to Groundwater Level Drops.
Creator: Alrowaimi, Mohamed, Chopra, Manoj, Nam, Boo Hyun, Yun, Hae-Bum, Sallam, Amr, University of Central Florida
Abstract / Description: Sinkholes are natural geohazard phenomena that cause damage to property and may lead to loss of life. They can also cause added pollution to the aquifer by draining unfiltered water from streams, wetland, and lakes into the aquifer. Sinkholes occur in a very distinctive karst geology where carbonate, limestone, dolomite, or gypsum, are encountered as the bedrock that can naturally be dissolved by groundwater circulating through them. Sinkholes can occur gradually or suddenly with catastrophic...
Show moreSinkholes are natural geohazard phenomena that cause damage to property and may lead to loss of life. They can also cause added pollution to the aquifer by draining unfiltered water from streams, wetland, and lakes into the aquifer. Sinkholes occur in a very distinctive karst geology where carbonate, limestone, dolomite, or gypsum, are encountered as the bedrock that can naturally be dissolved by groundwater circulating through them. Sinkholes can occur gradually or suddenly with catastrophic impact depending on the geology and hydrology of the area. Predicting the formation and the collapse of a sinkhole based on the current ground investigation technologies is limited by the high levels of uncertainties in the soil properties and behavior. It is possible that progressing sinkholes can be missed by geotechnical site investigations especially during the development of a very wide area. In this study, a laboratory-scale sinkhole model was constructed to physically simulate the sinkhole phenomenon. The physical model was designed to monitor a network of groundwater table over time around a predetermined sinkhole location. This model was designed to establish a correlation between the groundwater table drops and the sinkhole development. The experimental small-scale model showed that there is a groundwater cone of depression that forms prior the surface collapse of the sinkhole. The cone of water depression can be used to identify the potential location of the sinkhole at early stage of the overburden underground cavities formation in a reverse manner. In addition, monitoring of single groundwater well showed that groundwater level signal has some sudden water drops (progressive drops) which occur at different times (time lags) during the sinkhole development. A time frequency analysis was also used in this study to detect the pattern of these progressive drops of the groundwater table readings. It is observed, based on the model, that the development and growth of sinkhole can be correlated to progressive drops of the groundwater table since the drops start at the monitoring wells that are closer radially to the center of the sinkhole. Subsequently, with time, these drops get transferred to more distant monitoring wells. The time frequency analysis is used to decompose and detect the progressive drops by using a Pattern Detection Algorithm called Auto Modulating Detection Pattern Algorithm (AMD), which was developed by Yun (2013). The results of this analysis showed that the peaks of these progressive drops in the raw groundwater readings are a good indicator of the potential location of sinkholes at early stage when there are no any visible depression of the ground surface. Finally, the effect of several soil parameters on the cone of the water depression during the sinkhole formation is studied. The parametric study showed that both of overburden soil thickness and the initial (encountered) groundwater table level have a clear impact on the time of the sinkhole collapse. While this model used a predetermined crack location to study the groundwater level response around it, the concept of groundwater drops as an indicator of sinkhole progression and collapse may be used to determine the ultimate location of the sinkhole. By monitoring the changes in natural groundwater levels in the field from either an existing network of groundwater monitoring wells or additional installation, the methodology discussed in this dissertation may be used for possible foreseeing of the surface collapse of sinkholes.
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Date Issued: 2016
Identifier: CFE0006249, ucf:51060
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006249

Title: On-Chip Optical Stabilization of High-Speed Mode-locked Quantum Dot Lasers for Next Generation Optical Networks.
Creator: Ardey, Abhijeet, Delfyett, Peter, Chow, Lee, Peale, Robert, Likamwa, Patrick, University of Central Florida
Abstract / Description: Monolithic passively mode-locked colliding pulse semiconductor lasers generating pico- to sub-picosecond terahertz optical pulse trains are promising sources for future applications in ultra-high speed data transmission systems and optical measurements. However, in the absence of external synchronization, these passively mode-locked lasers suffer from large amplitude and timing jitter instabilities resulting in broad comb linewidths, which precludes many applications in the field of coherent...
Show moreMonolithic passively mode-locked colliding pulse semiconductor lasers generating pico- to sub-picosecond terahertz optical pulse trains are promising sources for future applications in ultra-high speed data transmission systems and optical measurements. However, in the absence of external synchronization, these passively mode-locked lasers suffer from large amplitude and timing jitter instabilities resulting in broad comb linewidths, which precludes many applications in the field of coherent communications and signal processing where a much narrower frequency line set is needed. In this dissertation, a novel quantum dot based coupled cavity laser is presented, where for the first time, four-wave mixing (FWM) in the monolithically integrated saturable absorber is used to injection lock a monolithic colliding pulse mode-locked (CPM) laser with a mode-locked high-Q ring laser. Starting with a passively mode-locked master ring laser, a stable 30 GHz optical pulse train is generated with more than 10 dB reduction in the RF noise level at 20 MHz offset and close to 3-times reduction in the average optical linewidth of the injection locked CPM slave laser. The FWM process is subsequently verified experimentally and conclusively shown to be the primary mechanism responsible for the observed injection locking. Other linear scattering effects are found to be negligible, as predicted in the orthogonal waveguide configuration. The novel injection locking technique is further exploited by employing optical hybrid mode-locking and increasing the Q of the master ring cavity, to realize an improved stabilization architecture. Dramatic reduction is shown with more than 14-times reduction in the photodetected beat linewidth and almost 5-times reduction in the optical linewidth of the injection locked slave laser with generation of close to transform limited pulses at ~ 30 GHz. These results demonstrate the effectiveness of the novel injection locking technique for an all-on-chip stability transfer and provides a new way of stabilizing monolithic optical pulse sources for applications in future high speed optical networks.
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Date Issued: 2014
Identifier: CFE0005299, ucf:50518
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005299

Title: NONLINEAR OPTICAL PROPERTIES OF ORGANIC CHROMOPHORES CALCULATED WITHIN TIME DEPENDENT DENSITY FUNCTIONAL THEORY.
Creator: Tafur, Sergio, Kokoouline, Viatcheslav, University of Central Florida
Abstract / Description: Time Dependent Density Functional Theory offers a good accuracy/computational cost ratio among different methods used to predict the electronic structure for molecules of practical interest. The Coupled Electronic Oscillator (CEO) formalism was recently shown to accurately predict Nonlinear Optical (NLO) properties of organic chromophores when combined with Time Dependent Density Functional Theory. Unfortunately, CEO does not lend itself easily to interpretation of the structure activity...
Show moreTime Dependent Density Functional Theory offers a good accuracy/computational cost ratio among different methods used to predict the electronic structure for molecules of practical interest. The Coupled Electronic Oscillator (CEO) formalism was recently shown to accurately predict Nonlinear Optical (NLO) properties of organic chromophores when combined with Time Dependent Density Functional Theory. Unfortunately, CEO does not lend itself easily to interpretation of the structure activity relationships of chromophores. On the other hand, the Sum Over States formalism in combination with semiempirical wavefunction methods has been used in the past for the design of simplified essential states models. These models can be applied to optimization of NLO properties of interest for applications. Unfortunately, TD-DFT can not be combined directly with SOS because state-to-state transition dipoles are not defined in the linear response TD approach. In this work, a second order CEO approach to TD-DFT is simplified so that properties of double excited states and state-to-state transition dipoles may be expressed through the combination of linear response properties. This approach is termed the a posteriori Tamm-Dancoff approximation (ATDA), and validated against high-level wavefunction theory methods. Sum over States (SOS) and related Two-Photon Transition Matrix formalism are then used to predict Two-Photon Absorption (2PA) profiles and anisotropy, as well as Second Harmonic Generation (SHG) properties. Numerical results for several conjugated molecules are in excellent agreement with CEO and finite field calculations, and reproduce experimental measurements well.
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Date Issued: 2007
Identifier: CFE0001853, ucf:47372
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001853

Title: PHONETIC AND ACOUSTIC ANALYSES OF TWO NEW CASES OF FOREIGN ACCENT SYNDROME.
Creator: Perkins, Rosalie, Ryalls, Jack, University of Central Florida
Abstract / Description: This study presents detailed phonetic and acoustic analyses of the speech characteristics of two new cases of Foreign Accent Syndrome (FAS). Participants include a 48-year-old female who began speaking with an "Eastern European" accent following a traumatic brain injury, and a 45-year-old male who presented with a "British" accent following a subcortical cerebral vascular accident (CVA). Identical samples of the participants' pre- and post-morbid speech were obtained, thus affording a new...
Show moreThis study presents detailed phonetic and acoustic analyses of the speech characteristics of two new cases of Foreign Accent Syndrome (FAS). Participants include a 48-year-old female who began speaking with an "Eastern European" accent following a traumatic brain injury, and a 45-year-old male who presented with a "British" accent following a subcortical cerebral vascular accident (CVA). Identical samples of the participants' pre- and post-morbid speech were obtained, thus affording a new level of control in the study of Foreign Accent Syndrome. The speech tasks consisted of oral readings of the Grandfather Passage and 18 real words comprised of the stop consonants /p/, /t/, /k/, /b/, /d/, /g/ combined with the peripheral vowels /i/, /a/ and /u/ and ending in a voiceless stop. Computer-based acoustic measures included: 1) voice onset time (VOT), 2) vowel durations, 3) whole word durations, 4) first, second and third formant frequencies, and 5) fundamental frequency. Formant frequencies were measured at three points in the vowel duration: a) 20%, b) 50%, and c) 80% to assess differences in vowel 'onglides' and 'offglides'. The phonetic analysis provided perceptual identification of the major phonetic features associated with the foreign quality of participant's FAS speech, while acoustic measures allowed precise quantification of these features. Results indicated evidence of backing of consonant and vowel productions for both participants. The implications for future research and clinical applications are also considered.
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Date Issued: 2007
Identifier: CFE0001916, ucf:47488
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001916

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