View All Items

Title: ABIOTIC DIFFERENCES BETWEEN GREEN TURTLE (CHELONIA MYDAS) NESTS IN NATURAL BEACH AND ENGINEERED DUNES: EFFECTS ON HATCHING SUCCESS.
Creator: Balfour, Martha, Fauth, John, University of Central Florida
Abstract / Description: Habitat loss is among the biggest threats to conservation worldwide, so habitat restoration plays an increasing role in endangered species management. This is especially true for species with high site fidelity, such as nesting marine turtles. Sand replenishment is commonly used to restore coastal beaches after severe erosion events, and may affect marine turtles and other species that live or reproduce in that habitat. I investigated how abiotic characteristics of sand used in a dune...
Show moreHabitat loss is among the biggest threats to conservation worldwide, so habitat restoration plays an increasing role in endangered species management. This is especially true for species with high site fidelity, such as nesting marine turtles. Sand replenishment is commonly used to restore coastal beaches after severe erosion events, and may affect marine turtles and other species that live or reproduce in that habitat. I investigated how abiotic characteristics of sand used in a dune restoration project at Archie Carr National Wildlife Refuge, Florida, affected reproduction of the federally-endangered green turtle (Chelonia mydas). Sand structure and composition can affect egg development and hatching success by altering nest conditions, with nests in fine-grain or very coarse sand suffering decreased hatching success. I determined that calcium carbonate content (27.0% Ã‚Â± 1.4 SE vs. 15.1% Ã‚Â± 3.8 SE), moisture content (3.29% Ã‚Â± 0.26 SE vs. 4.59% Ã‚Â± 0.25 SE), and grain size (427.53 μm Ã‚Â± 14.1 SE vs. 274.66 μm ÃƒÂƒÃ‚Â‚ÃƒÂ‚Ã‚Â± 29.1 SE) differed significantly between natural and restored dunes. Hatching success of green turtles (44.7% ÃƒÂƒÃ‚Â‚ÃƒÂ‚Ã‚Â± 6.2 SE vs. 65.8% Ã‚Â± 5.3 SE) was significantly lower on restored dunes compared to natural dunes with an estimated loss of 22,646 hatched eggs. Hatching success also decreased as the nesting season progressed. These results demonstrate the importance of regulating fill material used in beach restoration projects; substrate characteristics are easily evaluated and can significantly influence marine turtle hatching success.
Show less
Date Issued: 2010
Identifier: CFE0003376, ucf:48453
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003376

Title: Saturn's Rings: Measuring Particle Size Distributions Using Cassini UVIS Occultation Data.
Creator: Becker, Tracy, Colwell, Joshua, Fernandez, Yan, Campins, Humberto, Showalter, Mark, Klemm, Richard, University of Central Florida
Abstract / Description: Since its arrival to Saturn in 2004, the Cassini spacecraft has utilized its suite of sophisticated instruments to further our understanding of the Saturnian ring system. We analyze occultation data from Cassini's Ultraviolet Imaging Spectrograph (UVIS) in order to measure the particle size distribution and place limits on the minimum particle sizes in Saturn's rings.Throughout the ring system, particle accretion is countered by collisional and tidal disruption and Keplerian shear. Therefore,...
Show moreSince its arrival to Saturn in 2004, the Cassini spacecraft has utilized its suite of sophisticated instruments to further our understanding of the Saturnian ring system. We analyze occultation data from Cassini's Ultraviolet Imaging Spectrograph (UVIS) in order to measure the particle size distribution and place limits on the minimum particle sizes in Saturn's rings.Throughout the ring system, particle accretion is countered by collisional and tidal disruption and Keplerian shear. Therefore, the particle size distribution of the rings is continually evolving. The presence of sub-centimeter particles, which have short lifetimes due to these processes, is indicative of ongoing dynamics in the rings. Sub-centimeter-sized particles efficiently diffract light at ultraviolet wavelengths, and thus produce signatures of diffraction in the occultation data. The shape and intensity of the diffraction signatures are indicative of the sizes of the particles that produce them. The UVIS wavelength bandpass, 51.2 - 180 nm, contains the shortest wavelengths of the Cassini instruments, making it most sensitive to the smallest particles in the rings. We have developed a computational model that reconstructs the geometry of a UVIS observation and produces a synthetic diffraction signal for a given truncated power-law particle size distribution, which we compare with the observed signal. We implement this model for two sets of observations: (1) diffraction spikes at sharp ring edges during stellar occultations and (2) the light curve due to attenuated and diffracted sunlight by particles in Saturn's F ring during solar occultations. Near sharp ring edges, ring particles can diffract light such that there is a measurable increase in the signal of an unocculted star exterior to the ring. In Saturn's A ring, diffracted light can augment the stellar signal by up to 6% and can be detected tens of kilometers radially beyond the edge. The radial profile of the diffraction signal is dependent on the size distribution of the particle population near the ring edge. These diffraction signals are observed at sharp edges throughout Saturn's rings, although in this work we focus on diffraction at the outer edge of Saturn's A ring and at the edges of the Encke Gap. We find an overall steepening of the power-law size distribution and a decrease in the minimum particle size at the outer edge of the A ring when compared with the Encke Gap edges. This suggests that interparticle collisions caused by satellite perturbations in the region result in more shedding of regolith or fragmentation of particles in the outermost parts of the A ring. We rule out any significant population of sub-millimeter-sized particles in Saturn's A ring, placing a lower limitation of 1-mm on the minimum particle size in the ring.We also model the light curves produced as Saturn's F ring occults the Sun. We consider both the attenuated signal and the light diffracted by the particles in the ring during the occultation. Five of the eleven solar occultations analyzed show a clear signature of diffracted light that surpasses the unocculted solar signal. This includes a misaligned solar occultation that placed most of the solar disk outside of the instrument's field of view, reducing the solar signal by 97.5% and resulting in the serendipitous detection of diffracted light. We measure a large variation in the the size distribution of the particles that fill the broad, ~500 km region surrounding the F ring core. We find that smaller particles ((<) 50 micrometers) are present during solar occultations for which diffraction was detected, and place a lower limit on the minimum particle size of 100 micrometers for occultations during which diffraction was not detected. A comparison with images of the F ring observed by the Cassini Imaging Science Subsystem near the times of the occultations reveals that the detections of small particles in the UVIS data correspond with locations of collisional events in the F ring. This implies that collisions within the F ring core replenish the sub-millimeter-sized dust in the 500-km region that encompasses the F ring core.
Show less
Date Issued: 2016
Identifier: CFE0006073, ucf:50940
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006073

Title: The Intricate Relationship between Measures of Vocabulary Size and Lexical Diversity as Evidenced in Non-Native and Native Speaker Academic Compositions.
Creator: Gonzalez, Melanie, Folse, Keith, Bai, Haiyan, Mihai, Florin, Webb, Stuart, University of Central Florida
Abstract / Description: The present study, a quantitative lexical analysis, examines the extent to which vocabulary size and lexical diversity contribute to writing scores on advanced non-native speakers' and native speakers' academic compositions. The data consists of essays composed by 104 adult non-native English learners enrolled in advanced second language writing courses and 68 native speaking university students in a first-year composition course. The lexical diversity of the sample essays is quantified by...
Show moreThe present study, a quantitative lexical analysis, examines the extent to which vocabulary size and lexical diversity contribute to writing scores on advanced non-native speakers' and native speakers' academic compositions. The data consists of essays composed by 104 adult non-native English learners enrolled in advanced second language writing courses and 68 native speaking university students in a first-year composition course. The lexical diversity of the sample essays is quantified by both the Measure of Textual Lexical Diversity (MTLD) and the voc-D while vocabulary size is measured by CELEX word frequency means, three instruments that are available in the computational linguistics program Coh-Metrix 3.0. Writing scores are provided by three independent raters' evaluations according to the TOEFL iBT Independent Writing Rubric.Results from a binary logistic regression reveal that lexical diversity has a significantly greater impact on writing score than vocabulary size (p (<) .01). Nevertheless, a series of MANOVAs indicate that vocabulary size initially facilitates writing scores at the lower proficiency levels, but it is an essay's lexical diversity that promotes it to the higher score levels. Additional findings from the MANOVAs demonstrate that native speakers' profiles of lexical diversity and size are significantly different from their non-native peers (p (<) .001). The lexical profiles also differed significantly among the individual score levels of the TOEFL iBT rubric (p (<) .05). A final outcome from a Pearson's product moment correlation analysis shows that vocabulary size has only a moderate relationship to lexical diversity, suggesting that variation of mid-range vocabulary may be more important to writing proficiency than the use of more sophisticated terms that occur less frequently in natural language.Implications for practice suggest that it is not enough to simply teach vocabulary words in the L2 composition classroom, but also to guide learners in how to employ these words in a varied manner within their writing. Furthermore, the results of this study indicate that teachers should spend more time on helping students use medium frequency words along with synonyms of a similar frequency rather than teaching students infrequent vocabulary, which may appear to sound more advanced.
Show less
Date Issued: 2013
Identifier: CFE0004852, ucf:49693
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004852

Title: THE EFFECT OF COLLOIDAL STABILITY ON THE HEAT TRANSFER CHARACTERISTICS OF NANOSILICA DISPERSED FLUIDS.
Creator: Venkataraman, Manoj, Kumar, Ranganathan, University of Central Florida
Abstract / Description: Addition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and...
Show moreAddition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and commercialization of nanofluids. In this work, the stability of nano particles was studied by measuring the zeta potential of colloidal particles, particle concentration and size. Two different sizes of silica nano particles, 10 nm and 20 nm are used in this investigation at 0.2 vol. % and 0.5 vol. % concentrations. The measurements were made in deionized (DI) water, buffer solutions at various pH, DI water plus HCl acid solution (acidic pH) and DI water plus NaOH solution (basic pH). The stability or instability of silica dispersions in these solutions was related to the zeta potential of colloidal particles and confirmed by particle sizing measurements and independently by TEM observations. Low zeta potentials resulted in agglomeration as expected and the measured particle size was greater. The heat transfer characteristics of stable or unstable silica dispersions using the above solutions were experimentally determined by measuring heat flux as a function of temperature differential between a nichrome wire and the surrounding fluid. These experiments allowed the determination of the critical heat flux (CHF), which was then related to the dispersion characteristics of the nanosilica in various fluids described above. The thickness of the diffuse layer on nano particles was computed and experimentally confirmed in selected conditions for which there was no agglomeration. As the thickness of the diffuse layer decreased due to the increase in salt content or the ionic content, the electrostatic force of repulsion cease to exist and Van der Waal's force of agglomeration prevailed causing the particles to agglomerate affecting the CHF. The 10nm size silica particle dispersions showed better heat transfer characteristics compared to 20nm dispersion. It was also observed that at low zeta potential values, where agglomeration prevailed in the dispersion, the silica nano particles had a tendency to deposit on the nickel chromium wire used in CHF experiments. The thickness of the deposition was measured and the results show that with a very high deposition, CHF is enhanced due to the porosity on the wire. The 10nm size silica particles show higher CHF compared to 20nm silica particles. In addition, for both 10nm and 20nm silica particles, 0.5 vol. % concentration yielded higher heat transfer compared to 0.2 vol. % concentration. It is believed that although CHF is significantly increased with nano silica containing fluids compared to pure fluids, formation of particle clusters in unstable slurries will lead to detrimental long time performance, compared to that with stable silica dispersions.
Show less
Date Issued: 2005
Identifier: CFE0000837, ucf:46676
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000837

Title: THE EFFECT OF WEIGHT AND SIZE ON MENTAL ROTATION.
Creator: Furtak, Luke, Sims, Valerie, University of Central Florida
Abstract / Description: Shepard and Metzler (1971) argued that mental rotation is analogous to the real world in that people imagine the rotation of an object as if it were being physically rotated. This study tested this assertion by exposing participants to physical shapes that increased in size and weight. Participants interacted with blocks designed after Shepard and Metzler mental rotation size that differed in size and weight then performed subsequent mental rotation. We found no difference in reaction time...
Show moreShepard and Metzler (1971) argued that mental rotation is analogous to the real world in that people imagine the rotation of an object as if it were being physically rotated. This study tested this assertion by exposing participants to physical shapes that increased in size and weight. Participants interacted with blocks designed after Shepard and Metzler mental rotation size that differed in size and weight then performed subsequent mental rotation. We found no difference in reaction time but found that increased size reduced accuracy. We discuss the implications of this study as they pertain to embodied cognition.
Show less
Date Issued: 2014
Identifier: CFH0004711, ucf:45399
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004711

Title: Nano-pipette as nanoparticle analyzer and capillary gated ion transistor.
Creator: Rudzevich, Yauheni, Chow, Lee, Heinrich, Helge, Schulte, Alfons, Yuan, Jiann-Shiun, University of Central Florida
Abstract / Description: The ability to precisely count inorganic and organic nanoparticles and to measure their size distribution plays a major role in various applications such as drug delivery, nanoparticles counting, and many others. In this work I present a simple resistive pulse method that allows translocations, counting, and measuring the size and velocity distribution of silica nanoparticles and liposomes with diameters from 50 nm to 250 nm. This technique is based on the Coulter counter technique, but has...
Show moreThe ability to precisely count inorganic and organic nanoparticles and to measure their size distribution plays a major role in various applications such as drug delivery, nanoparticles counting, and many others. In this work I present a simple resistive pulse method that allows translocations, counting, and measuring the size and velocity distribution of silica nanoparticles and liposomes with diameters from 50 nm to 250 nm. This technique is based on the Coulter counter technique, but has nanometer size pores. It was found that ionic current drops when nanoparticles enter the nanopore of a pulled micropipette, producing a clear translocation signal. Pulled borosilicate micropipettes with opening 50 ~ 350 nm were used as the detecting instrument. This method provides a direct, fast and cost-effective way to characterize inorganic and organic nanoparticles in a solution. In this work I also introduce a newly developed Capillary Ionic Transistor (CIT). It is presented as a nanodevice which provides control of ionic transport through nanochannel by gate voltage. CIT is Ionic transistor, which employs pulled capillary as nanochannel with a tip diameter smaller than 100 mm. We observed that the gate voltage applied to gate electrode, deposited on the outer wall of a capillary, affect a conductance of nanochannel, due to change of surface charge at the solution/capillary interface. Negative gate voltage corresponds to lower conductivity and positive gate increases conductance of the channel. This effect strongly depends on the size of the channel. In general, at least one dimension of the channel has to be small enough for electrical double layer to overlap.
Show less
Date Issued: 2014
Identifier: CFE0005880, ucf:50882
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005880

Title: Comparing the Receptive Vocabulary Knowledge of Intermediate-level Students of Different Native languages in an Intensive English Program.
Creator: Alkhofi, Anas, Folse, Keith, Mihai, Florin, Purmensky, Kerry, Xu, Lihua, University of Central Florida
Abstract / Description: Because most(-)if not all(-)intensive English programs (IEP) assign students to specific levels based on a placement test that does not involve any form of explicit vocabulary testing, some degree of variation in lexical knowledge of students within an individual class should not be surprising. However, very little research has ever quantified this variation. The current study fills the gap in this important area of TESOL research by investigating vocabulary variation among intermediate-level...
Show moreBecause most(-)if not all(-)intensive English programs (IEP) assign students to specific levels based on a placement test that does not involve any form of explicit vocabulary testing, some degree of variation in lexical knowledge of students within an individual class should not be surprising. However, very little research has ever quantified this variation. The current study fills the gap in this important area of TESOL research by investigating vocabulary variation among intermediate-level students at one IEP. Participants (N=79) were split into two main proficiency groups, high intermediate (N=28) and low intermediate (N=51). The 2K, 3K, and 5K levels from the Vocabulary Levels Test (VLT) were used as a vocabulary measure. In this study, VLT scores were analyzed by proficiency level and by students' original individual classes (N=7). The results revealed considerable vocabulary variation. In some instances, vocabulary size varied by 900 word families per student. First language influence was also investigated by comparing the largest two language groups in the sample, Arabic (N= 28) and Spanish (N=12). Spanish-speaking students significantly outperformed the Arabic speaking students in all vocabulary measures (except for the 2K level). The study, therefore, raises questions about the approaches used in teaching a class that has both Spanish and Arabic speakers. Implications and suggestions for further studies are discussed.
Show less
Date Issued: 2015
Identifier: CFE0005569, ucf:50281
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005569

Title: Understanding How, Where and How much Freight Flows Using 2012 Commodity Flow Survey Data.
Creator: Keya, Nowreen, Eluru, Naveen, Abdel-Aty, Mohamed, Anowar, Sabreena, Uddin, Nizam, University of Central Florida
Abstract / Description: In recent years, with increased economic globalization, growing e-commerce and internet based shopping, freight movement patterns are undergoing a transformative change. The shipment size distribution is moving towards a higher share of smaller size shipments affecting transportation mode and vehicle type requirements. In addition, freight transportation mode is closely affected by the destination location (and its attributes). In our dissertation, we contribute to freight research by...
Show moreIn recent years, with increased economic globalization, growing e-commerce and internet based shopping, freight movement patterns are undergoing a transformative change. The shipment size distribution is moving towards a higher share of smaller size shipments affecting transportation mode and vehicle type requirements. In addition, freight transportation mode is closely affected by the destination location (and its attributes). In our dissertation, we contribute to freight research by developing a comprehensive framework to examine the how, where and how much freight flows in US. Specifically, we study the following dimensions of freight flow: (1) transportation mode, (2) mode and shipment weight choice and (3) mode and destination choice. For analyzing mode choice, an advanced discrete freight mode choice model- a hybrid utility-regret based model system has been estimated while accommodating for shipper level unobserved heterogeneity. To demonstrate the applicability of the proposed model system, detailed policy analyses examining the implementation of vehicle fleet automation and rerouting of freight movements away from a region were considered. While shipment weight could be considered as an explanatory variable in modeling mode choice (or vice-versa), it is more likely that the decision of mode and shipment choice is a simultaneous process. This joint decision is investigated both simultaneously employing a closed form copula structure and sequentially employing latent segmentation based sequence model. For destination choice, we investigated the connection between shipping mode and destination choice of shipment in a latent segmentation based sequential form. The analysis for the dissertation is conducted using 2012 Commodity Flow Survey (CFS) data.
Show less
Date Issued: 2018
Identifier: CFE0007574, ucf:52569
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007574

Title: X-ray Scattering Investigations of Metallic Thin Films.
Creator: Warren, Andrew, Coffey, Kevin, Sohn, Yongho, Suryanarayana, Challapalli, Heinrich, Helge, Barmak, Katayun, Toney, Michael, University of Central Florida
Abstract / Description: Nanometric thin films are used widely throughout various industries and for various applications. Metallic thin films, specifically, are relied upon extensively in the microelectronics industry, among others. For example, alloy thin films are being investigated for CMOS applications, tungsten films find uses as contacts and diffusion barriers, and copper is used often as interconnect material. Appropriate metrology methods must therefore be used to characterize the physical properties of...
Show moreNanometric thin films are used widely throughout various industries and for various applications. Metallic thin films, specifically, are relied upon extensively in the microelectronics industry, among others. For example, alloy thin films are being investigated for CMOS applications, tungsten films find uses as contacts and diffusion barriers, and copper is used often as interconnect material. Appropriate metrology methods must therefore be used to characterize the physical properties of these films. X-ray scattering experiments are well suited for the investigation of nano-scaled systems, and are the focus of this doctoral dissertation. Emphasis is placed on (1) phase identification of polycrystalline thin films, (2) the evaluation of the grain size and microstrain of metallic thin films by line profile analysis, and (3) the study of morphological evolution in solid/solid interfaces.To illustrate the continued relevance of x-ray diffraction for phase identification of simple binary alloy systems, Pt-Ru thin films, spanning the compositional range from pure Pt to pure Ru were investigated. In these experiments, a meta-stable extension of the HCP phase is observed in which the steepest change in the electronic work function coincides with a rapid change in the c/a ratio of the HCP phase.For grain size and microstrain analysis, established line profile methods are discussed in terms of Cu and W thin film analysis. Grain sizes obtained by x-ray diffraction are compared to transmission electron microscopy based analyses. Significant discrepancies between x-ray and electron microscopy are attributed to sub-grain misorientations arising from dislocation core spreading at the film/substrate interface. A novel "residual" full width half max parameter is introduced for examining the contribution of strain to x-ray peak broadening. The residual width is subsequently used to propose an empirical method of line profile analysis for thin films on substrates.X-ray reflectivity was used to study the evolution of interface roughness with annealing for a series of Cu thin films that were encapsulated in both SiO2 and Ta/SiO2. While all samples follow similar growth dynamics, notable differences in the roughness evolution with high temperature ex-situ annealing were observed. The annealing resulted in a smoothing of only one interface for the SiO2 encapsulated films, while neither interface of the Ta/SiO2 encapsulated films evolved significantly. The fact that only the upper Cu/SiO2 interface evolves is attributed to mechanical pinning of the lower interface to the rigid substrate. The lack of evolution of the Cu/Ta/SiO2 interface is consistent with the lower diffusivity expected of Cu in a Cu/Ta interface as compared to that in a Cu/SiO2 interface. The smoothing of the upper Cu/SiO2 interface qualitatively follows that expected for capillarity driven surface diffusion but with notable quantitative deviation.
Show less
Date Issued: 2013
Identifier: CFE0004770, ucf:49784
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004770

Title: An Investigation of Online Tools and Teaching, Social, and Cognitive Presence in a Large Hybrid Online Class.
Creator: Rath, Victoria, Gunter, Glenda, Boote, David, Holt, Larry, Hornik, Steven, University of Central Florida
Abstract / Description: The purpose of this research study was to explore the impact of specific Web 2.0 tools on students' experience of teaching, social, and cognitive presence and motivation when enrolled in a very large hybrid course. With online course enrollments continuing to grow at a higher rate than traditional enrollments in higher education (Allen (&) Seaman, 2011) and universities increasing class sizes as a way to meet this demand with fewer fiscal resources, it is imperative to find ways to keep...
Show moreThe purpose of this research study was to explore the impact of specific Web 2.0 tools on students' experience of teaching, social, and cognitive presence and motivation when enrolled in a very large hybrid course. With online course enrollments continuing to grow at a higher rate than traditional enrollments in higher education (Allen (&) Seaman, 2011) and universities increasing class sizes as a way to meet this demand with fewer fiscal resources, it is imperative to find ways to keep students engaged and motivated when enrolled in very large classes. This study used the Community of Inquiry framework (Garrison, Anderson (&) Archer, 2000) to examine the effect of specific Web 2.0 tools (asynchronous discussion, streaming lectures, multimedia lecture demonstrations, Twitter, and the Second Life virtual world) on teaching, social, and cognitive presence and motivation. The sample population for this study (n = 567) consisted of undergraduate students enrolled in a very large hybrid accounting course in the fall of 2010 at the University of Central Florida. The total enrollment for the course was 943 students. Students could attend face-to-face (f2f) class sessions in a large lecture room that seated 285 students or they could view a streaming video capture of the lectures online. Students were not required to attend the f2f class sessions and could complete the course entirely online.Data were analyzed using one-way analysis of variances (ANOVA), and results of the statistical analyses indicated that students who frequently used the Web 2.0 tools had statistically significant higher mean motivation scores than students who did not use the tools as frequently. Additionally, students who frequently attended the f2f sessions had statistically significant higher mean social presence scores compared to students who attended sometimes or not at all. Attending the f2f sessions, however, did not result in higher mean scores of teaching or cognitive presence.When examined for the impact of the specific Web 2.0 tools, analysis of the ANOVA results indicated that students who used the discussion, streaming lectures, multimedia lecture demonstrations, and Twitter all of the time had significantly higher mean scores of teaching, social, and cognitive presence compared to those students who used the tools less frequently. Further research should be conducted on large hybrid and online courses in different content areas and on those that use different types of learning approaches.
Show less
Date Issued: 2012
Identifier: CFE0004638, ucf:49890
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004638

Title: Investigation of infrared thermography for subsurface damage detection of concrete structures.
Creator: Hiasa, Shuhei, Catbas, Necati, Tatari, Omer, Nam, Boo Hyun, Zaurin, Ricardo, Xanthopoulos, Petros, University of Central Florida
Abstract / Description: Deterioration of road infrastructure arises from aging and various other factors. Consequently, inspection and maintenance have been a serious worldwide problem. In the United States, degradation of concrete bridge decks is a widespread problem among several bridge components. In order to prevent the impending degradation of bridges, periodic inspection and proper maintenance are indispensable. However, the transportation system faces unprecedented challenges because the number of aging...
Show moreDeterioration of road infrastructure arises from aging and various other factors. Consequently, inspection and maintenance have been a serious worldwide problem. In the United States, degradation of concrete bridge decks is a widespread problem among several bridge components. In order to prevent the impending degradation of bridges, periodic inspection and proper maintenance are indispensable. However, the transportation system faces unprecedented challenges because the number of aging bridges is increasing under limited resources, both in terms of budget and personnel. Therefore, innovative technologies and processes that enable bridge owners to inspect and evaluate bridge conditions more effectively and efficiently with less human and monetary resources are desired. Traditionally, qualified engineers and inspectors implemented hammer sounding and/or chain drag, and visual inspection for concrete bridge deck evaluations, but these methods require substantial field labor, experience, and lane closures for bridge deck inspections. Under these circumstances, Non-Destructive Evaluation (NDE) techniques such as computer vision-based crack detection, impact echo (IE), ground-penetrating radar (GPR) and infrared thermography (IRT) have been developed to inspect and monitor aging and deteriorating structures rapidly and effectively. However, no single method can detect all kinds of defects in concrete structures as well as the traditional inspection combination of visual and sounding inspections; hence, there is still no international standard NDE methods for concrete bridges, although significant progress has been made up to the present.This research presents the potential to reduce a burden of bridge inspections, especially for bridge decks, in place of traditional chain drag and hammer sounding methods by IRT with the combination of computer vision-based technology. However, there were still several challenges and uncertainties in using IRT for bridge inspections. This study revealed those challenges and uncertainties, and explored those solutions, proper methods and ideal conditions for applying IRT in order to enhance the usability, reliability and accuracy of IRT for concrete bridge inspections. Throughout the study, detailed investigations of IRT are presented. Firstly, three different types of infrared (IR) cameras were compared under active IRT conditions in the laboratory to examine the effect of photography angle on IRT along with the specifications of cameras. The results showed that when IR images are taken from a certain angle, each camera shows different temperature readings. However, since each IR camera can capture temperature differences between sound and delaminated areas, they have a potential to detect delaminated areas under a given condition in spite of camera specifications even when they are utilized from a certain angle. Furthermore, a more objective data analysis method than just comparing IR images was explored to assess IR data. Secondly, coupled structural mechanics and heat transfer models of concrete blocks with artificial delaminations used for a field test were developed and analyzed to explore sensitive parameters for effective utilization of IRT. After these finite element (FE) models were validated, critical parameters and factors of delamination detectability such as the size of delamination (area, thickness and volume), ambient temperature and sun loading condition (different season), and the depth of delamination from the surface were explored. This study presents that the area of delamination is much more influential in the detectability of IRT than thickness and volume. It is also found that there is no significant difference depending on the season when IRT is employed. Then, FE model simulations were used to obtain the temperature differences between sound and delaminated areas in order to process IR data. By using this method, delaminated areas of concrete slabs could be detected more objectively than by judging the color contrast of IR images. However, it was also found that the boundary condition affects the accuracy of this method, and the effect varies depending on the data collection time. Even though there are some limitations, integrated use of FE model simulation with IRT showed that the combination can be reduce other pre-tests on bridges, reduce the need to have access to the bridge and also can help automate the IRT data analysis process for concrete bridge deck inspections. After that, the favorable time windows for concrete bridge deck inspections by IRT were explored through field experiment and FE model simulations. Based on the numerical simulations and experimental IRT results, higher temperature differences in the day were observed from both results around noontime and nighttime, although IRT is affected by sun loading during the daytime heating cycle resulting in possible misdetections. Furthermore, the numerical simulations show that the maximum effect occurs at night during the nighttime cooling cycle, and the temperature difference decreases gradually from that time to a few hours after sunrise of the next day. Thus, it can be concluded that the nighttime application of IRT is the most suitable time window for bridge decks. Furthermore, three IR cameras with different specifications were compared to explore several factors affecting the utilization of IRT in regards to subsurface damage detection in concrete structures, specifically when the IRT is utilized for high-speed bridge deck inspections at normal driving speeds under field laboratory conditions. The results show that IRT can detect up to 2.54 cm delamination from the concrete surface at any time period. This study revealed two important factors of camera specifications for high-speed inspection by IRT as shorter integration time and higher pixel resolution.Finally, a real bridge was scanned by three different types of IR cameras and the results were compared with other NDE technologies that were implemented by other researchers on the same bridge. When compared at fully documented locations with 8 concrete cores, a high-end IR camera with cooled detector distinguished sound and delaminated areas accurately. Furthermore, indicated location and shape of delaminations by three IR cameras were compared to other NDE methods from past research, and the result revealed that the cooled camera showed almost identical shapes to other NDE methods including chain drag. It should be noted that the data were collected at normal driving speed without any lane closures, making it a more practical and faster method than other NDE technologies. It was also presented that the factor most likely to affect high-speed application is integration time of IR camera as well as the conclusion of the field laboratory test.The notable contribution of this study for the improvement of IRT is that this study revealed the preferable conditions for IRT, specifically for high-speed scanning of concrete bridge decks. This study shows that IRT implementation under normal driving speeds has high potential to evaluate concrete bridge decks accurately without any lane closures much more quickly than other NDE methods, if a cooled camera equipped with higher pixel resolution is used during nighttime. Despite some limitations of IRT, the data collection speed is a great advantage for periodic bridge inspections compared to other NDE methods. Moreover, there is a high possibility to reduce inspection time, labor and budget drastically if high-speed bridge deck scanning by the combination of IRT and computer vision-based technology becomes a standard bridge deck inspection method. Therefore, the author recommends combined application of the high-speed scanning combination and other NDE methods to optimize bridge deck inspections.
Show less
Date Issued: 2016
Identifier: CFE0006323, ucf:51575
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006323

Title: Sampling and Subspace Methods for Learning Sparse Group Structures in Computer Vision.
Creator: Jaberi, Maryam, Foroosh, Hassan, Pensky, Marianna, Gong, Boqing, Qi, GuoJun, Pensky, Marianna, University of Central Florida
Abstract / Description: The unprecedented growth of data in volume and dimension has led to an increased number of computationally-demanding and data-driven decision-making methods in many disciplines, such as computer vision, genomics, finance, etc. Research on big data aims to understand and describe trends in massive volumes of high-dimensional data. High volume and dimension are the determining factors in both computational and time complexity of algorithms. The challenge grows when the data are formed of the...
Show moreThe unprecedented growth of data in volume and dimension has led to an increased number of computationally-demanding and data-driven decision-making methods in many disciplines, such as computer vision, genomics, finance, etc. Research on big data aims to understand and describe trends in massive volumes of high-dimensional data. High volume and dimension are the determining factors in both computational and time complexity of algorithms. The challenge grows when the data are formed of the union of group-structures of different dimensions embedded in a high-dimensional ambient space.To address the problem of high volume, we propose a sampling method referred to as the Sparse Withdrawal of Inliers in a First Trial (SWIFT), which determines the smallest sample size in one grab so that all group-structures are adequately represented and discovered with high probability. The key features of SWIFT are: (i) sparsity, which is independent of the population size; (ii) no prior knowledge of the distribution of data, or the number of underlying group-structures; and (iii) robustness in the presence of an overwhelming number of outliers. We report a comprehensive study of the proposed sampling method in terms of accuracy, functionality, and effectiveness in reducing the computational cost in various applications of computer vision. In the second part of this dissertation, we study dimensionality reduction for multi-structural data. We propose a probabilistic subspace clustering method that unifies soft- and hard-clustering in a single framework. This is achieved by introducing a delayed association of uncertain points to subspaces of lower dimensions based on a confidence measure. Delayed association yields higher accuracy in clustering subspaces that have ambiguities, i.e. due to intersections and high-level of outliers/noise, and hence leads to more accurate self-representation of underlying subspaces. Altogether, this dissertation addresses the key theoretical and practically issues of size and dimension in big data analysis.
Show less
Date Issued: 2018
Identifier: CFE0007017, ucf:52039
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007017

Cu (3)	+ -
Cassini (2)	+ -
Occultations (2)	+ -
Planetary Rings (2)	+ -
class size (2)	+ -

size (2)	+ -
student achievement (2)	+ -
vocabulary size (2)	+ -
Agglomeration (1)	+ -
Alteration of resistivity (1)	+ -
Au (1)	+ -
Bayes (1)	+ -
Big Data (1)	+ -
Big Data Analysis (1)	+ -
Bigram Frequency (1)	+ -
Biosensor (1)	+ -
Buffer Sizing (1)	+ -
Burnout (1)	+ -
Capillarity (1)	+ -
Characterization (1)	+ -
Chinese Characters (1)	+ -
Class Size (1)	+ -
Classical Size Effect (1)	+ -
Clustering (1)	+ -
Commodity Flow Survey Data (1)	+ -
Community of Inquiry (1)	+ -
Confidence Intervals (1)	+ -
Copula (1)	+ -
Crash patterns (1)	+ -
DMA (1)	+ -

ETD Collection (28)	+ -
Honors Collection (4)	+ -

English (31)	+ -
Engilsh (1)	+ -

University of Central Florida (32)	+ -
Bai, Haiyan (2)	+ -
Coffey, Kevin (2)	+ -
Colwell, Joshua (2)	+ -
Fernandez, Yan (2)	+ -

Search In

Pages

Pages

Sort Results By:

Narrow results by:

Topical Subject

Collection

Type of Resource

Language

Creator

Format

Owner