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Title: Effect of Acute L-Alanyl-L-Glutamine (Sustamine) and Electrolyte Ingestion on Cognitive Function, Multiple Object Tracking and Reaction Time Following Prolonged Exercise.
Creator: Pruna, Gabriel, Hoffman, Jay, Stout, Jeffrey, Fragala, Maren, University of Central Florida
Abstract / Description: Changes in physiological function occurring during a body water deficit may result in significant decrements in performance, cognitive function and fine motor control during exercise. This may be due to the magnitude of the body water deficit. Rehydration strategies are important to prevent these deleterious effects in performance. The purpose of this study was to examine the changes before and after prolonged exercise of an alanine-glutamine dipeptide (AG) on cognitive function and reaction...
Show moreChanges in physiological function occurring during a body water deficit may result in significant decrements in performance, cognitive function and fine motor control during exercise. This may be due to the magnitude of the body water deficit. Rehydration strategies are important to prevent these deleterious effects in performance. The purpose of this study was to examine the changes before and after prolonged exercise of an alanine-glutamine dipeptide (AG) on cognitive function and reaction time.Twelve male endurance-trained runners (age: 23.5 (&)#177; 3.7 y; height: 175.5 (&)#177; 5.4 cm; weight: 70.7 (&)#177; 7.6 kg) participated in this study. Participants were asked to run on a treadmill at 70% of their predetermined VO2max for 1 h and then run at 90% of VO2max until volitional exhaustion on four separate days (T1-T4). T1 was a dehydration trial and T2-T4 were all different hydration modalities (electrolyte drink, electrolyte drink with a low dose of AG, electrolyte drink with a high dose of AG, respectively) where the participants drank 250 mL every 15 min. Before and after each hour run, cognitive function and reaction tests were administered. Hopkins Magnitude Based Inferences were used to analyze cognitive function and reaction time data.Results showed that physical reaction time was likely faster for the low dose trial than the high dose trial. Dehydration had a possible negative effect on the number of hits in 60-sec compared to both the low and high dose trials. Comparisons between only the electrolyte drink and the high dose ingestion appeared to be possibly negative. Analysis of lower body quickness indicates that performance in both the low and high dose trials were likely improved (decreased) in comparison to the dehydration trial. Multiple object tracking analysis indicated a possible greater performance for dehydration and low dose compared to only the electrolyte drink, while there was a likely greater performance in multiple object tracking for the high dose trial compared to consumption of the electrolyte drink only. The serial subtraction test was possibly greater in the electrolyte drink trial compared to dehydration.Rehydration with the alanine-glutamine dipeptide during an hour run at a submaximal intensity appears to maintain or enhance subsequent visual reaction time in both upper and lower body activities compared to a no hydration trial. The combination of the alanine-glutamine dipeptide may have enhanced fluid and electrolyte absorption from the gut and possibly into skeletal tissue to maintain neuromuscular performance.
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Date Issued: 2014
Identifier: CFE0005233, ucf:50583
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005233

Title: Potential Relationship Between Vascular Depression and Autobiographical Memory Specificity in an Older Adult Population According to the CaR-FA-X Model.
Creator: Herrera Legon, Manuel, Paulson, Daniel, Rapport, Mark, Sims, Valerie, University of Central Florida
Abstract / Description: Vascular depression is a type of depression that has its onset later in life, and it has been associated with cardiovascular or metabolic diseases. Depression can be costly and associated with other health problems, which is why it becomes imperative to uncover the multiple mechanisms of action for depression symptomatology. A proposed mechanism of action for the emergence of depressive symptomatology is poor autobiographical memory specificity according to the CaR-FA-X model. However, it...
Show moreVascular depression is a type of depression that has its onset later in life, and it has been associated with cardiovascular or metabolic diseases. Depression can be costly and associated with other health problems, which is why it becomes imperative to uncover the multiple mechanisms of action for depression symptomatology. A proposed mechanism of action for the emergence of depressive symptomatology is poor autobiographical memory specificity according to the CaR-FA-X model. However, it remains unclear whether this mechanism contributes somehow to the vascular depression specific type. The purpose of this research was to determine the potential relationship between the mechanisms proposed by the CaR-FA-X model and the presence of vascular depression, which has not been addressed by previous literature or research. Forty three older adults over the age of seventy from the Orlando area completed multiple measures including the Geriatric Depression Scale, Autobiographical Memory Test, and physiological measures. Results showed no support for a relationship between CaR-FA-X model elements and vascular depression; however, support was found for the relationship between cerebrovascular burden and depression as proposed by the vascular depression theory with rumination serving as a moderator. To our knowledge, this is the first time a study finds the moderating effect of rumination in the development of vascular depression. Further studies will need to address other potential mechanisms that increase risk for this specific type of depression as well as investigate the reasons under which, if any, autobiographical memory specificity might be related to vascular depression by using other measures that might be more sensitive to a non-clinical population.
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Date Issued: 2018
Identifier: CFE0007014, ucf:52041
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007014

Title: Evaluation of crash modification factors and functions including time trends at intersections.
Creator: Wang, Jung-Han, Abdel-Aty, Mohamed, Radwan, Essam, Eluru, Naveen, Lee, JaeYoung, Wang, Chung-Ching, University of Central Florida
Abstract / Description: Traffic demand has increased as population increased. The US population reached 313,914,040 in 2012 (US Census Bureau, 2015). Increased travel demand may have potential impact on roadway safety and the operational characteristics of roadways. Total crashes and injury crashes at intersections accounted for 40% and 44% of traffic crashes, respectively, on US roadways in 2007 according to the Intersection Safety Issue Brief (FHWA, 2009). Traffic researchers and engineers have developed a...
Show moreTraffic demand has increased as population increased. The US population reached 313,914,040 in 2012 (US Census Bureau, 2015). Increased travel demand may have potential impact on roadway safety and the operational characteristics of roadways. Total crashes and injury crashes at intersections accounted for 40% and 44% of traffic crashes, respectively, on US roadways in 2007 according to the Intersection Safety Issue Brief (FHWA, 2009). Traffic researchers and engineers have developed a quantitative measure of the safety effectiveness of treatments in the form of crash modification factors (CMF). Based on CMFs from multiple studies, the Highway Safety Manual (HSM) Part D (AASHTO, 2010) provides CMFs which can be used to determine the expected number of crash reduction or increase after treatments were installed. Even though CMFs have been introduced in the HSM, there are still limitations that require to be investigated. One important potential limitation is that the HSM provides various CMFs as fixed values, rather than CMFs under different configurations. In this dissertation, the CMFs were estimated using the observational before-after study to show that the CMFs vary across different traffic volume levels when signalizing intersections. Besides screening the effect of traffic volume, previous studies showed that CMFs could vary over time after the treatment was implemented. Thus, in this dissertation, the trends of CMFs for the signalization and adding red light running cameras (RLCs) were evaluated. CMFs for these treatments were measured in each month and 90- day moving windows using the time series ARMA model. The results of the signalization show that the CMFs for rear-end crashes were lower at the early phase after the signalization but gradually increased from the 9th month. Besides, it was also found that the safety effectiveness is significantly worse 18 months after installing RLCs.Although efforts have been made to seek reliable CMFs, the best estimate of CMFs is still widely debated. Since CMFs are non-zero estimates, the population of all CMFs does not follow normal distributions and even if it did, the true mean of CMFs at some intersections may be different than that at others. Therefore, a bootstrap method was proposed to estimate CMFs that makes no distributional assumptions. Through examining the distribution of CMFs estimated by bootstrapped resamples, a CMF precision rating method is suggested to evaluate the reliability of the estimated CMFs. The result shows that the estimated CMF for angle+left-turn crashes after signalization has the highest precision, while estimates of the CMF for rear-end crashes are extremely unreliable. The CMFs for KABCO, KABC, and KAB crashes proved to be reliable for the majority of intersections, but the estimated effect of signalization may not be accurate at some sites.In addition, the bootstrap method provides a quantitative measure to identify the reliability of CMFs, however, the CMF transferability is questionable. Since the development of CMFs requires safety performance functions (SPFs), could CMFs be developed using the SPFs from other states in the United States? This research applies the empirical Bayes method to develop CMFs using several SPFs from different jurisdictions and adjusted by calibration factors. After examination, it is found that applying SPFs from other jurisdictions is not desired when developing CMFs.The process of estimating CMFs using before-after studies requires the understanding of multiple statistical principles. In order to simplify the process of CMF estimation and make the CMFs research reproducible. This dissertation includes an open source statistics package built in R (R, 2013) to make the estimation accessible and reproducible. With this package, authorities are able to estimate reliable CMFs following the procedure suggested by FHWA. In addition, this software package equips a graphical interface which integrates the algorithm of calculating CMFs so that users can perform CMF calculation with minimum programming prerequisite. Expected contributions of this study are to 1) propose methodologies for CMFs to assess the variation of CMFs with different characteristics among treated sites, 2) suggest new objective criteria to judge the reliability of safety estimation, 3) examine the transferability of SPFs when developing CMF using before-after studies, and 4) develop a statistics software to calculate CMFs. 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: 2016
Identifier: CFE0006413, ucf:51454
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006413

Title: Rumination and executive dysfunction: Risk factors for vascular depression.
Creator: Brush, David, Paulson, Daniel, Rapport, Mark, Bohil, Corey, University of Central Florida
Abstract / Description: Introduction: The widely-supported vascular depression hypothesis is underspecified with respect to cognitive mechanisms by which high cerebrovascular burden (CVB) and neuropathology relate to depressive symptoms. Integration of the vascular depression hypothesis with the CaR-FA-X model, a framework of affect regulation mechanisms, suggest that Rumination (R) and executive dysfunction (X) may increase due to altered recruitment of the dorsolateral prefrontal cortex resulting from high CVB and...
Show moreIntroduction: The widely-supported vascular depression hypothesis is underspecified with respect to cognitive mechanisms by which high cerebrovascular burden (CVB) and neuropathology relate to depressive symptoms. Integration of the vascular depression hypothesis with the CaR-FA-X model, a framework of affect regulation mechanisms, suggest that Rumination (R) and executive dysfunction (X) may increase due to altered recruitment of the dorsolateral prefrontal cortex resulting from high CVB and underlying neuropathology. This process would contribute to depressive symptomatology among older adults with high CVB. The progression of examined hypotheses included mediation models examining mechanistic relationships between predictors (CVB, DLPFC activation), cognitive correlates (rumination, executive functioning), and affective outcomes (depressive symptoms). Method: A sample of 52 community-dwelling, stroke-free, individuals over the age of 70, without history of severe mental illness, dementia, or severe cognitive impairment, completed the Ruminative Responses Scale, provided self-reported cerebrovascular burden data (cardiac disease, hypertension, diabetes, high cholesterol), and completed executive function tasks (Stroop, Flanker) while their hemodynamic response was measured using fNIRS. The Geriatric Depression Scale was used to assess depressive symptomatology. Prefrontal cortical recruitment was assessed using functional near-infrared spectroscopy (fNIRS).Results: A progression of conventional and bootstrapped regression-based models broadly supported relationships between CVB and depressive symptoms, but not between DLPFC activation and depressive symptoms. No mechanistic relationships were found, with respect to analyses testing prospective cognitive mediators.Conclusions: Primary findings from this study indicate that cerebrovascular burden predicts depressive symptomatology among older adults and is related to a reduction in inhibitory control ability. Further, these findings inform CVB measurement and mental health implications of contrasting approaches to CVB measurement. A primary contribution of this thesis is that results appear to support utilization of fNIRS, a low-cost and accessible neuroimaging paradigm, for the study of lateralized cognition among older adults.
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Date Issued: 2018
Identifier: CFE0006981, ucf:51648
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006981

Title: PHOSPHOLIPASE A2MECHANISM OF INTERFACIAL ACTIVATION,AN INTERDISCLIPLINARY APPROACH.
Creator: Nemec, Kathleen, Tatulian, Suren, University of Central Florida
Abstract / Description: Phospholipase A2 (PLA2) is an enzyme that hydrolyzes the sn-2-ester bond of membrane phospholipids and liberates arachidonic acid, which is converted to eicosanoids that act as potent mediators of inflammation and allergy. As such this enzyme plays a crucial role in many homeostatic physiological and immunologic processes and disease progression. PLA2s undergo substantial increase in activity upon binding to cellular membranes. This effect of interfacial activation is well recognized, yet its...
Show morePhospholipase A2 (PLA2) is an enzyme that hydrolyzes the sn-2-ester bond of membrane phospholipids and liberates arachidonic acid, which is converted to eicosanoids that act as potent mediators of inflammation and allergy. As such this enzyme plays a crucial role in many homeostatic physiological and immunologic processes and disease progression. PLA2s undergo substantial increase in activity upon binding to cellular membranes. This effect of interfacial activation is well recognized, yet its structural and physical aspects are poorly understood. In this work, we have employed the interdisciplinary methods of molecular biology, biochemistry, biophysics, bioinformatics and computational biology, in order to elucidate the structure-function relationships mediating the interfacial activation of human group IIA and group IB PLA2 isoforms. We have evaluated the structural and functional consequences of two conservative, single residue substitutions, located at key membrane-binding and substrate-binding positions of hIIA PLA2. We have also evaluated a human group IB fragment (hIBdeltaN10), missing the first 10 N-terminal residues which make up the N-terminal alpha helix, as well as a chimeric enzyme substituting the N-terminal alpha helix of hIB PLA2 with that from hIIA PLA2 (hIIA/IB PLA2). We have compared the engineered proteins against both the hIIA and hIB PLA2 native enzymes and their N-terminal peptides, N10-hIB and N10-hIIA, respectively. We have developed and used a novel multidisciplinary approach in order to position the segmentally labeled hIB PLA2 and hIIA/IB chimeric PLA2s at the membrane surface. The results of this work provide significant insight into the understanding of the physical aspects of interfacial activation by determining the precise membrane binding modes of PLA2 isoforms and identifying certain amino acid residues and whole protein segments that play key roles in membrane binding, activation, and involved allosteric conformational effects in PLA2s.
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Date Issued: 2006
Identifier: CFE0001324, ucf:47015
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001324

Title: DENSITY-FUNCTIONAL THEORY APPLIED TO PROBLEMS IN CATALYSIS AND ELECTROCHEMISTRY.
Creator: Kumar, Santosh, Schelling, Patrick, University of Central Florida
Abstract / Description: We study the structure and energetics of water molecules adsorbed at ceria (111) surfaces below one monolayer coverage using density-functional theory. The results of this study provide a theoretical framework for interpreting recent experimental results on the redox properties of water at ceria (111) surfaces. In particular, we have computed the structure and energetics of various absorption geometries at stoichiometric ceria (111) surface. In contrast to experiment results, we do not find a...
Show moreWe study the structure and energetics of water molecules adsorbed at ceria (111) surfaces below one monolayer coverage using density-functional theory. The results of this study provide a theoretical framework for interpreting recent experimental results on the redox properties of water at ceria (111) surfaces. In particular, we have computed the structure and energetics of various absorption geometries at stoichiometric ceria (111) surface. In contrast to experiment results, we do not find a strong coverage dependence of the adsorption energy. For the case of reduced surface, our results show that it may not be energetically favorable for water to oxidize oxygen vacancy site at the surface. Instead, oxygen vacancies tend to result in water more strongly binding to the surface. The result of this attractive water-vacancy interaction is that the apparent concentration of oxygen vacancies at the surface is enhanced in the presence of water. Finally, we discuss this problem with reference to recent experimental and theoretical studies of vacancy clustering at the (111) ceria surface. We also describe the simulation results for the structure and dynamics of liquid water using the SIESTA electronic structure approach. We find that the structure of water depends strongly on the particular basis set used. Applying a systematic approach to varying the basis set, we find that the basis set which results in good agreement with experimental binding energies for isolated water dimers also provides a reasonable description of the radial distribution functions of liquid water. We show that the structure of liquid water varies in a systematic fashion with the choice of basis set. Comparable to many other first-principle studies of liquid water using gradient-corrected density functionals, the liquid is found to be somewhat overstructured. The possibility of further improvements through a better choice of the basis set is discussed. We find that while improvements are likely to be possible, application to large-scale systems will require use of a computational algorithm whose computational cost scales linearly with system size. Finally, we study the molecular and atomic adsorption of oxygen on the gold nano-clusters. We show multiple stable and metastable structures for atomically and molecularly adsorbed oxygen to the gold cluster. We plan to predict the reaction pathway and calculate activation energy barrier for desorption of molecular oxygen from the atomically adsorbed gold cluster which is very important for any catalytic reaction occurring using gold nanoparticles.
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Date Issued: 2006
Identifier: CFE0001211, ucf:46938
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001211

Title: AN OCEAN SURFACE WIND VECTOR MODEL FUNCTION FOR A SPACEBORNE MICROWAVE RADIOMETER AND ITS APPLICATION.
Creator: Soisuvarn, Seubson, Jones, W. Linwood, University of Central Florida
Abstract / Description: Ocean surface wind vectors over the ocean present vital information for scientists and forecasters in their attempt to understand the Earth's global weather and climate. As the demand for global wind velocity information has increased, the number of satellite missions that carry wind-measuring sensors has also increased; however, there are still not sufficient numbers of instruments in orbit today to fulfill the need for operational meteorological and scientific wind vector data. Over the...
Show moreOcean surface wind vectors over the ocean present vital information for scientists and forecasters in their attempt to understand the Earth's global weather and climate. As the demand for global wind velocity information has increased, the number of satellite missions that carry wind-measuring sensors has also increased; however, there are still not sufficient numbers of instruments in orbit today to fulfill the need for operational meteorological and scientific wind vector data. Over the last three decades operational measurements of global ocean wind speeds have been obtained from passive microwave radiometers. Also, vector ocean surface wind data were primarily obtained from several scatterometry missions that have flown since the early 1990's. However, other than SeaSat-A in 1978, there has not been combined active and passive wind measurements on the same satellite until the launch of the second Advanced Earth Observing Satellite (ADEOS-II) in 2002. This mission has provided a unique data set of coincident measurements between the SeaWinds scatterometer and the Advanced Microwave Scanning Radiometer (AMSR). AMSR observes the vertical and horizontal brightness temperature (TB) at six frequency bands between 6.9 GHz and 89.0 GHz. Although these measurements contain some wind direction information, the overlying atmospheric influence can easily obscure this signal and make wind direction retrieval from passive microwave measurements very difficult. However, at radiometer frequencies between 10 and 37 GHz, a certain linear combination of vertical and horizontal brightness temperatures causes the atmospheric dependence to be nearly cancelled and surface parameters such as wind speed, wind direction and sea surface temperature to dominate the resulting signal. This brightness temperature combination may be expressed as ATBV-TBH, where A is a constant to be determined and the TBV and TBH are the brightness temperatures for the vertical and horizontal polarization respectively. In this dissertation, an empirical relationship between the AMSR's ATBV-TBH and SeaWinds' surface wind vector retrievals was established for three microwave frequencies: 10, 18 and 37 GHz. This newly developed model function for a passive microwave radiometer could provide the basis for wind vector retrievals either separately or in combination with scatterometer measurements.
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Date Issued: 2006
Identifier: CFE0001493, ucf:47088
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001493

Title: IMPROVING PROJECT MANAGEMENT WITH SIMULATION AND COMPLETION DISTRIBUTION FUNCTIONS.
Creator: Cates, Grant, Mollaghasemi, Mansooreh, University of Central Florida
Abstract / Description: Despite the critical importance of project completion timeliness, management practices in place today remain inadequate for addressing the persistent problem of project completion tardiness. Uncertainty has been identified as a contributing factor in late projects. This uncertainty resides in activity duration estimates, unplanned upsetting events, and the potential unavailability of critical resources. This research developed a comprehensive simulation based methodology for conducting...
Show moreDespite the critical importance of project completion timeliness, management practices in place today remain inadequate for addressing the persistent problem of project completion tardiness. Uncertainty has been identified as a contributing factor in late projects. This uncertainty resides in activity duration estimates, unplanned upsetting events, and the potential unavailability of critical resources. This research developed a comprehensive simulation based methodology for conducting quantitative project completion-time risk assessments. The methodology enables project stakeholders to visualize uncertainty or risk, i.e. the likelihood of their project completing late and the magnitude of the lateness, by providing them with a completion time distribution function of their projects. Discrete event simulation is used to determine a project's completion distribution function. The project simulation is populated with both deterministic and stochastic elements. Deterministic inputs include planned activities and resource requirements. Stochastic inputs include activity duration growth distributions, probabilities for unplanned upsetting events, and other dynamic constraints upon project activities. Stochastic inputs are based upon past data from similar projects. The time for an entity to complete the simulation network, subject to both the deterministic and stochastic factors, represents the time to complete the project. Multiple replications of the simulation are run to create the completion distribution function. The methodology was demonstrated to be effective for the on-going project to assemble the International Space Station. Approximately $500 million per month is being spent on this project, which is scheduled to complete by 2010. Project stakeholders participated in determining and managing completion distribution functions. The first result was improved project completion risk awareness. Secondly, mitigation options were analyzed to improve project completion performance and reduce total project cost.
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Date Issued: 2004
Identifier: CFE0000209, ucf:46243
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000209

Title: AN INTRODUCTION TO HELLMANN-FEYNMAN THEORY.
Creator: Wallace, David, Ismail, Mourad, University of Central Florida
Abstract / Description: The Hellmann-Feynman theorem is presented together with certain allied theorems. The origin of the Hellmann-Feynman theorem in quantum physical chemistry is described. The theorem is stated with proof and with discussion of applicability and reliability. Some adaptations of the theorem to the study of the variation of zeros of special functions and orthogonal polynomials are surveyed. Possible extensions are discussed.
Date Issued: 2005
Identifier: CFE0000403, ucf:46349
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000403

Title: THE SHEFFER B-TYPE 1 ORTHOGONAL POLYNOMIAL SEQUENCES.
Creator: Galiffa, Daniel, Ismail, Mourad, University of Central Florida
Abstract / Description: In 1939, I.M. Sheffer proved that every polynomial sequence belongs to one and only one $type$. Sheffer extensively developed properties of the $B$-\emph{Type 0} polynomial sequences and determined which sets are also orthogonal. He subsequently generalized his classification method to the case of arbitrary $B$-\emph{Type k} by constructing the generalized generating function $A(t)\mathrm=\sum_^\infty$, with $H_i(t)=h_t^i+h_t^+\cdots,\phantomh_\neq 0$. Although extensive research has been...
Show moreIn 1939, I.M. Sheffer proved that every polynomial sequence belongs to one and only one $type$. Sheffer extensively developed properties of the $B$-\emph{Type 0} polynomial sequences and determined which sets are also orthogonal. He subsequently generalized his classification method to the case of arbitrary $B$-\emph{Type k} by constructing the generalized generating function $A(t)\mathrm=\sum_^\infty$, with $H_i(t)=h_t^i+h_t^+\cdots,\phantomh_\neq 0$. Although extensive research has been done on characterizing polynomial sequences, no analysis has yet been completed on sets of type one or higher ($k\geq1$). We present a preliminary analysis of a special case of the $B$-\emph{Type 1} ($k=1$) class, which is an extension of the $B$-\emph{Type 0} class, in order to determine which sets, if any, are also orthogonal sets. Lastly, we consider an extension of this research and comment on future considerations. In this work the utilization of computer algebra packages is indispensable, as computational difficulties arise in the $B$-\emph{Type 1} class that are unlike those in the $B$-\emph{Type 0} class.
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Date Issued: 2009
Identifier: CFE0002551, ucf:47655
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002551

Title: MESHFREE APPROXIMATION METHODS FOR FREE-FORM OPTICAL SURFACES WITH APPLICATIONS TO HEAD-WORN DISPLAYS.
Creator: Cakmakci, Ozan, Rolland, Jannick, University of Central Florida
Abstract / Description: Compact and lightweight optical designs achieving acceptable image quality, field of view, eye clearance, eyebox size, operating across the visible spectrum, are the key to the success of next generation head-worn displays. The first part of this thesis reports on the design, fabrication, and analysis of off-axis magnifier designs. The first design is catadioptric and consists of two elements. The lens utilizes a diffractive optical element and the mirror has a free-form surface described...
Show moreCompact and lightweight optical designs achieving acceptable image quality, field of view, eye clearance, eyebox size, operating across the visible spectrum, are the key to the success of next generation head-worn displays. The first part of this thesis reports on the design, fabrication, and analysis of off-axis magnifier designs. The first design is catadioptric and consists of two elements. The lens utilizes a diffractive optical element and the mirror has a free-form surface described with an x-y polynomial. A comparison of color correction between doublets and single layer diffractive optical elements in an eyepiece as a function of eye clearance is provided to justify the use of a diffractive optical element. The dual-element design has an 8 mm diameter eyebox, 15 mm eye clearance, 20 degree diagonal full field, and is designed to operate across the visible spectrum between 450-650 nm. 20% MTF at the Nyquist frequency with less than 3% distortion has been achieved in the dual-element head-worn display. An ideal solution for a head-worn display would be a single free-form surface mirror design. A single surface mirror does not have dispersion; therefore, color correction is not required. A single surface mirror can be made see-through by machining the appropriate surface shape on the opposite side to form a zero power shell. The second design consists of a single off-axis free-form mirror described with an x-y polynomial, which achieves a 3 mm diameter exit pupil, 15 mm eye relief, and a 24 degree diagonal full field of view. The second design achieves 10% MTF at the Nyquist frequency set by the pixel spacing of the VGA microdisplay with less than 3% distortion. Both designs have been fabricated using diamond turning techniques. Finally, this thesis addresses the question of "what is the optimal surface shape for a single mirror constrained in an off-axis magnifier configuration with multiple fields?" Typical optical surfaces implemented in raytrace codes today are functions mapping two dimensional vectors to real numbers. The majority of optical designs to-date have relied on conic sections and polynomials as the functions of choice. The choice of conic sections is justified since conic sections are stigmatic surfaces under certain imaging geometries. The choice of polynomials from the point of view of surface description can be challenged. A polynomial surface description may link a designer's understanding of the wavefront aberrations and the surface description. The limitations of using multivariate polynomials are described by a theorem due to Mairhuber and Curtis from approximation theory. This thesis proposes and applies radial basis functions to represent free-form optical surfaces as an alternative to multivariate polynomials. We compare the polynomial descriptions to radial basis functions using the MTF criteria. The benefits of using radial basis functions for surface description are summarized in the context of specific head-worn displays. The benefits include, for example, the performance increase measured by the MTF, or the ability to increase the field of view or pupil size. Even though Zernike polynomials are a complete and orthogonal set of basis over the unit circle and they can be orthogonalized for rectangular or hexagonal pupils using Gram-Schmidt, taking practical considerations into account, such as optimization time and the maximum number of variables available in current raytrace codes, for the specific case of the single off-axis magnifier with a 3 mm pupil, 15 mm eye relief, 24 degree diagonal full field of view, we found the Gaussian radial basis functions to yield a 20% gain in the average MTF at 17 field points compared to a Zernike (using 66 terms) and an x-y polynomial up to and including 10th order. The linear combination of radial basis function representation is not limited to circular apertures. Visualization tools such as field map plots provided by nodal aberration theory have been applied during the analysis of the off-axis systems discussed in this thesis. Full-field displays are used to establish node locations within the field of view for the dual-element head-worn display. The judicious separation of the nodes along the x-direction in the field of view results in well-behaved MTF plots. This is in contrast to an expectation of achieving better performance through restoring symmetry via collapsing the nodes to yield field-quadratic astigmatism.
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Date Issued: 2008
Identifier: CFE0002479, ucf:47674
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002479

Title: APPLICATION OF STATISTICAL METHODS IN RISK AND RELIABILITY.
Creator: Heard, Astrid, Pensky, Marianna, University of Central Florida
Abstract / Description: The dissertation considers construction of confidence intervals for a cumulative distribution function F(z) and its inverse at some fixed points z and u on the basis of an i.i.d. sample where the sample size is relatively small. The sample is modeled as having the flexible Generalized Gamma distribution with all three parameters being unknown. This approach can be viewed as an alternative to nonparametric techniques which do not specify distribution of X and lead to less efficient procedures....
Show moreThe dissertation considers construction of confidence intervals for a cumulative distribution function F(z) and its inverse at some fixed points z and u on the basis of an i.i.d. sample where the sample size is relatively small. The sample is modeled as having the flexible Generalized Gamma distribution with all three parameters being unknown. This approach can be viewed as an alternative to nonparametric techniques which do not specify distribution of X and lead to less efficient procedures. The confidence intervals are constructed by objective Bayesian methods and use the Jeffreys noninformative prior. Performance of the resulting confidence intervals is studied via Monte Carlo simulations and compared to the performance of nonparametric confidence intervals based on binomial proportion. In addition, techniques for change point detection are analyzed and further evaluated via Monte Carlo simulations. The effect of a change point on the interval estimators is studied both analytically and via Monte Carlo simulations.
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Date Issued: 2005
Identifier: CFE0000736, ucf:46565
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000736

Title: THE ROLE OF COMMUNITY COLLEGE REGISTRARS IN RELATION TO STUDENT INFORMATION SYSTEMS IMPLEMENTATION.
Creator: Lepley, Sandra, House, Jesse, University of Central Florida
Abstract / Description: This study examined the effects of implementing Web-enabled technology systems on the functional role of the community college registrar. The focus on systems implementation included in-house, outsourced, consortia, or combination of implementation strategies. A quantitative and qualitative approach included several interviews and a mailed survey questionnaire. The researcher developed the instrument from human resources position description forms, an adapted administrative Q-sort technique,...
Show moreThis study examined the effects of implementing Web-enabled technology systems on the functional role of the community college registrar. The focus on systems implementation included in-house, outsourced, consortia, or combination of implementation strategies. A quantitative and qualitative approach included several interviews and a mailed survey questionnaire. The researcher developed the instrument from human resources position description forms, an adapted administrative Q-sort technique, and a role conflict and ambiguity perception questionnaire. The study targeted the members of the American Association of Collegiate Registrars and Admissions Officers. The research findings indicated that some aspects of perceived role, role conflict (harmony), and ambiguity (clarity) were different for registrars whose colleges used in-house, outsourced, consortium, or a combination of implementation strategies, and for certain background characteristics. For example, the study identified different levels of involvement for some duties and some differences in collaboration among divisions and departments within institutions and with other organizations. Suggested uses of the research results include professional development programming for more efficient technology implementation. The research instrument could be adapted to study functional role of other job positions, implementation projects, and administrative strategies.
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Date Issued: 2006
Identifier: CFE0001161, ucf:46869
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001161

Title: APPLICATION OF TRAINED POD-RBF TO INTERPOLATION IN HEAT TRANSFER AND FLUID MECHANICS.
Creator: Ashley, Rebecca A, Kassab, Alain, University of Central Florida
Abstract / Description: To accurately model or predict future operating conditions of a system in engineering or applied mechanics, it is necessary to understand its fundamental principles. These may be the material parameters, defining dimensional characteristics, or the boundary conditions. However, there are instances when there is little to no prior knowledge of the system properties or conditions, and consequently, the problem cannot be modeled accurately. It is therefore critical to define a method that can...
Show moreTo accurately model or predict future operating conditions of a system in engineering or applied mechanics, it is necessary to understand its fundamental principles. These may be the material parameters, defining dimensional characteristics, or the boundary conditions. However, there are instances when there is little to no prior knowledge of the system properties or conditions, and consequently, the problem cannot be modeled accurately. It is therefore critical to define a method that can identify the desired characteristics of the current system without accumulating extensive computation time. This thesis formulates an inverse approach using proper orthogonal decomposition (POD) with an accompanying radial basis function (RBF) interpolation network. This method is capable of predicting the desired characteristics of a specimen even with little prior knowledge of the system. This thesis first develops a conductive heat transfer problem, and by using the truncated POD - RBF interpolation network, temperature values are predicted given a varying Biot number. Then, a simple bifurcation problem is modeled and solved for velocity profiles while changing the mass flow rate. This bifurcation problem provides the data and foundation for future research into the left ventricular assist device (LVAD) and implementation of POD - RBF. The trained POD - RBF inverse approach defined in this thesis can be implemented in several applications of engineering and mechanics. It provides model reduction, error filtration, regularization and an improvement over previous analysis utilizing computational fluid dynamics (CFD).
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Date Issued: 2018
Identifier: CFH2000279, ucf:45782
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000279

Title: EFFECTIVENESS OF CARDIAC REHABILITATION: SECONDARY PREVENTION INCREASES FUNCTIONAL CAPACITY IN POST-MYOCARDIAL INFARCTION PATIENTS.
Creator: Badillo, Kristin, Fisher, Thomas, University of Central Florida
Abstract / Description: The purpose of this study was to discern the effectiveness of Cardiac Rehabilitation/ Secondary Prevention Programs (CR/ SPPs) by evaluating increased functional capacity in the form of MET (metabolic equivalent) scores post-myocardial infarction (MI) or heart attack. The Duke Activity Status Index (DASI) survey is administered as part of the Standard Operating Procedure (SOP) for participation in the Secondary Prevention Program. Criterion for the research included patients 65 and older,...
Show moreThe purpose of this study was to discern the effectiveness of Cardiac Rehabilitation/ Secondary Prevention Programs (CR/ SPPs) by evaluating increased functional capacity in the form of MET (metabolic equivalent) scores post-myocardial infarction (MI) or heart attack. The Duke Activity Status Index (DASI) survey is administered as part of the Standard Operating Procedure (SOP) for participation in the Secondary Prevention Program. Criterion for the research included patients 65 and older, with a history of one myocardial infarction, and had completed all 36 sessions of CR. The scores from 11 SPP surveys were analyzed and compared in three time increments from sessions 1-18 (initial, or"pre"), sessions 19-36 ("pan"), and sessions 1-36 ("post"). A total of 11 (n=11) surveys were collected and analyzed at The Computing and Statistical Technology Laboratory in Education (CASTLE) in the Teaching Academy on UCF Main Campus. Results from the data showed mean MET scores of 6.21 at session 1, 7.59 at session 18, and 8.15 at session 36. The mean changes over time represented in METs were 1.38 (1), .56 (18), and 1.93 (36). Percent changes over time were 27% (1), 8% (18), and 36% (36). This study showed increased functional capacity over time and will improve program design in terms of frequency and duration.
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Date Issued: 2015
Identifier: CFH0004770, ucf:45339
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004770

Title: IMPROVING FMRI CLASSIFICATION THROUGH NETWORK DECONVOLUTION.
Creator: Martinek, Jacob, Zhang, Shaojie, University of Central Florida
Abstract / Description: The structure of regional correlation graphs built from fMRI-derived data is frequently used in algorithms to automatically classify brain data. Transformation on the data is performed during pre-processing to remove irrelevant or inaccurate information to ensure that an accurate representation of the subject's resting-state connectivity is attained. Our research suggests and confirms that such pre-processed data still exhibits inherent transitivity, which is expected to obscure the true...
Show moreThe structure of regional correlation graphs built from fMRI-derived data is frequently used in algorithms to automatically classify brain data. Transformation on the data is performed during pre-processing to remove irrelevant or inaccurate information to ensure that an accurate representation of the subject's resting-state connectivity is attained. Our research suggests and confirms that such pre-processed data still exhibits inherent transitivity, which is expected to obscure the true relationships between regions. This obfuscation prevents known solutions from developing an accurate understanding of a subject's functional connectivity. By removing correlative transitivity, connectivity between regions is made more specific and automated classification is expected to improve. The task of utilizing fMRI to automatically diagnose Attention Deficit/Hyperactivity Disorder was posed by the ADHD-200 Consortium in a competition to draw in researchers and new ideas from outside of the neuroimaging discipline. Researchers have since worked with the competition dataset to produce ever-increasing detection rates. Our approach was empirically tested with a known solution to this problem to compare processing of treated and untreated data, and the detection rates were shown to improve in all cases with a weighted average increase of 5.88%.
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Date Issued: 2015
Identifier: CFH0004895, ucf:45410
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004895

Title: INTEGRATION OF A NANOSTRUCTURE EMBEDDED THERMORESPONSIVE POLYMER FOR MICROFLUIDIC APPLICATIONS.
Creator: Londe, Ghanashyam, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: This work describes the modeling, synthesis, integration and characterization of a novel nanostructure embedded thermoresponsive material for microfluidic applications. The innumerable applications of thermoresponsive surfaces in the recent years have necessitated the development of a rigorous mathematical treatment for these surfaces to understand and improve their behavior. An analytical model is proposed to describe the transfer characteristic (variation of contact angle versus temperature...
Show moreThis work describes the modeling, synthesis, integration and characterization of a novel nanostructure embedded thermoresponsive material for microfluidic applications. The innumerable applications of thermoresponsive surfaces in the recent years have necessitated the development of a rigorous mathematical treatment for these surfaces to understand and improve their behavior. An analytical model is proposed to describe the transfer characteristic (variation of contact angle versus temperature) of a unique switchable, nanostructured, thermoresponsive surface consisting of silica nanoparticles and the thermoresponsive polymer, Poly(N-isopropylacrylamide ) (PNIPAAm) which changes its wetting angle upon heating. Important metrics such as the absolute lower critical solution temperature, threshold & saturation temperatures and gain are modeled and quantified by mathematical expressions. Based on the modeling, a heat source for the thermoresponsive surface was integrated on the glass substrate itself to create a fully functional smart surface. The design and fabrication of a smart platform consisting of the switchable, nanostructured, thermoresponsive surface with an integrated gold microheater for wettability control and its time response analysis was conducted. The insight gained into the behavior of the thermoresponsive surface by using the analytical model, aided the effort in the effective integration of the surface into a microfluidic channel for flow regulation applications. The implementations of novel microfluidic flow regulator concepts were tested. The aim is to integrate a regulator function to a channel surface utilizing the layer-by-layer (LBL) deposition technique. The characterization and pressure differential study of the microfluidic regulators was carried out on simple straight microchannels which were selectively coated with the thermoresponsive surface. Theoretical and experimental studies were performed to determine the important characteristic parameters including capillary, Weber and Reynolds numbers. The pressure differential data was used to develop critical operating specifications. This work lays out a new microfluidic device concept consisting of a channel with a built-in regulatory function.
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Date Issued: 2008
Identifier: CFE0002368, ucf:47786
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002368

Title: Investigating and Facilitating the Transferability of Safety Performance Functions.
Creator: Farid, Ahmed Tarek Ahmed, Abdel-Aty, Mohamed, Lee, JaeYoung, Eluru, Naveen, University of Central Florida
Abstract / Description: Safety performance functions (SPFs) are essential analytical tools in the road safety field. The SPFs are statistical regression models used to predict crash counts by roadway facility type, crash type and severity. The national Highway Safety Manual (HSM) is a generic guidebook used for road safety evaluation and enhancement. In it, default SPFs, developed using negative binomial (NB) regression, are provided for multiple facility types and crash categories. Roadway agencies, whether public...
Show moreSafety performance functions (SPFs) are essential analytical tools in the road safety field. The SPFs are statistical regression models used to predict crash counts by roadway facility type, crash type and severity. The national Highway Safety Manual (HSM) is a generic guidebook used for road safety evaluation and enhancement. In it, default SPFs, developed using negative binomial (NB) regression, are provided for multiple facility types and crash categories. Roadway agencies, whether public or private, may opt to not invest their resources in data collection and processing to develop own localized SPFs. Instead, the agencies may adopt the HSM's. However, the HSM's SPFs may not necessarily be applicable to any conditions. Hence, this research is focused on SPF transferability, specifically for rural divided multilane highway segments. Use of Bayesian informative priors to aid in the transferability of NB SPFs, developed for Florida, to California's conditions and vice versa is investigated. It is demonstrated that informative priors facilitate SPF transferability. Furthermore, NB SPFs are developed for Florida, Ohio, Illinois, Minnesota, California, Washington and North Carolina. That is to evaluate the transferability of each state's SPFs to the other states' conditions. The results indicate that Ohio, Illinois, Minnesota and California have SPFs that are transferable to conditions of each of the four states. Also, two methods are proposed for calibrating transferred SPFs to the destinations' conditions and are shown to outperform the SPF calibration methods in the road safety literature. Finally, a variety of modeling frameworks are proposed for developing and transferring SPFs of the seven aforementioned states to each state's data. Not a single model exhibits the best fit when transferred in all cases. However, the Tobit model, NB model and a hybrid model that coalesces the results of both perform the best in a substantial number of the transferred SPFs.
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Date Issued: 2018
Identifier: CFE0007000, ucf:52054
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007000

Title: A Localized Blended RBF Collocation Method for Effective Shock Capturing.
Creator: Harris, Michael, Kassab, Alain, Moslehy, Faissal, Divo, Eduardo, Chopra, Manoj, University of Central Florida
Abstract / Description: Solving partial differential equations (PDEs) can require numerical methods, especially for non-linear problems and complex geometry. Common numerical methods used today are the finite difference method (FDM), finite element method (FEM) and the finite volume method (FVM). These methods require a mesh or grid before a solution is attempted. Developing the mesh can require expensive preprocessing time and the quality of the mesh can have major effects on the solution. In recent years, meshless...
Show moreSolving partial differential equations (PDEs) can require numerical methods, especially for non-linear problems and complex geometry. Common numerical methods used today are the finite difference method (FDM), finite element method (FEM) and the finite volume method (FVM). These methods require a mesh or grid before a solution is attempted. Developing the mesh can require expensive preprocessing time and the quality of the mesh can have major effects on the solution. In recent years, meshless methods have become a research interest due to the simplicity of using scattered data points. Many types of meshless methods exist stemming from the spectral or pseudo-spectral methods, but the focus of this research involves a meshless method using radial basis function (RBF) interpolation. Radial basis functions (RBF) interpolation is a class of meshless method and can be used in solving partial differential equations. Radial basis functions are impressive because of the capability of multivariate interpolation over scattered data, even for data with discontinuities. Also, radial basis function interpolation is capable of spectral accuracy and exponential convergence. For infinitely smooth radial basis functions such as the Hardy Multiquadric and inverse Multiquadric, the RBF is dependent on a shape parameter that must be chosen properly to obtain accurate approximations. The optimum shape parameter can vary depending on the smoothness of the field. Typically, the shape parameter is chosen to be a large value rendering the RBF flat and yielding high condition number interpolation matrix. This strategy works well for smooth data and as shown to produce phenomenal results for problems in heat transfer and incompressible fluid dynamics. The approach of flat RBF or high condition matrices tends to fail for steep gradients and shocks. Instead, a low-value shape parameter rendering the RBF steep and the condition number of the interpolation matrix small should be used in the presence of steep gradients or shocks. This work demonstrates a method to capture steep gradients and shocks using a blended RBF approach. The method switches between flat and steep RBF interpolation depending on the smoothness of the data. Flat RBF or high condition number RBF interpolation is used for smooth regions maintaining high accuracy. Steep RBF or low condition number RBF interpolation provides stability for steep gradients and shocks. This method is demonstrated using several numerical experiments such as 1-D advection equation, 2-D advection equation, Burgers equation, 2-D inviscid compressible Euler equations, and the Navier-Stokes equations.
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Date Issued: 2018
Identifier: CFE0007332, ucf:52108
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007332

Title: From Excited Charge Dynamics to Cluster Diffusion: Development and Application of Techniques Beyond DFT and KMC.
Creator: Acharya, Shree Ram, Rahman, Talat, Chow, Lee, Stolbov, Sergey, Wu, Annie, University of Central Florida
Abstract / Description: This dissertation focuses on developing reliable and accurate computational techniques which enable the examination of static and dynamic properties of various activated phenomena using deterministic and stochastic approaches. To explore ultrafast electron dynamics in materials with strong electron-electron correlation, under the influence of a laser pulse, an ab initio electronic structure method based on time-dependent density functional theory (TDDFT) in combination with dynamical mean...
Show moreThis dissertation focuses on developing reliable and accurate computational techniques which enable the examination of static and dynamic properties of various activated phenomena using deterministic and stochastic approaches. To explore ultrafast electron dynamics in materials with strong electron-electron correlation, under the influence of a laser pulse, an ab initio electronic structure method based on time-dependent density functional theory (TDDFT) in combination with dynamical mean field theory (DMFT) is developed and applied to: 1) single-band Hubbard model; 2) multi-band metal Ni; and 3) multi-band insulator MnO. The ultrafast demagnetization in Ni reveal the importance of memory and correlation effects, leading to much better agreement with experimental data than previously obtained, while for MnO the main channels of charge response are identified. Furthermore, an analytical form of the exchange-correlation kernel is obtained for future applications, saving tremendous computational cost. In another project, size-dependent temporal and spatial evolution of homo- and hetero-epitaxial adatom islands on fcc(111) transition metals surfaces are investigated using the self-learning kinetic Monte Carlo (SLKMC) method that explores long-time dynamics unbiased by apriori selected diffusion processes. Novel multi-atom diffusion processes are revealed. Trends in the diffusion coefficients point to the relative role of adatom lateral interaction and island-substrate binding energy in determining island diffusivity. Moreover, analysis of the large data-base of the activation energy barriers generated for multitude of diffusion processes for variety of systems allows extraction of a set of descriptors that in turn generate predictive models for energy barrier evaluation. Finally, the kinetics of the industrially important methanol partial oxidation reaction on a model nanocatalyst is explored using KMC supplemented by DFT energetics. Calculated thermodynamics explores the active surface sites for reaction components including different intermediates and energetics of competing probable reaction pathways, while kinetic study attends to the selectivity of products and its variation with external factors.
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Date Issued: 2018
Identifier: CFE0006965, ucf:52910
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006965

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