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Title: MODELING OF LIQUID CRYSTAL DISPLAY AND PHOTONIC DEVICES.
Creator: Ge, Zhibing, Wu, Shin-Tson, University of Central Florida
Abstract / Description: Liquid crystal (LC) materials have been widely applied in electro-optical devices, among which display is the most successful playground and numerous new applications in photonic areas (such as laser beam steering devices) are also emerging. To well guide the device design for optimum performance, accurate modeling is of prior and practical importance. Generally, the modeling of LC devices includes two parts in sequence: accurate LC molecule deformation extraction under external electric...
Show moreLiquid crystal (LC) materials have been widely applied in electro-optical devices, among which display is the most successful playground and numerous new applications in photonic areas (such as laser beam steering devices) are also emerging. To well guide the device design for optimum performance, accurate modeling is of prior and practical importance. Generally, the modeling of LC devices includes two parts in sequence: accurate LC molecule deformation extraction under external electric fields and optical calculation thereafter for the corresponding electro-optical behaviors. In this dissertation, first, hybrid finite element method and finite difference method are developed to minimize the free energy of the LC systems. In this part of study, with computer-aided derivation, the full forms of the LC free energy equations without any simplification can be obtained. Besides, Galerkin's method and weak form technique are further introduced to successfully degrade the high order nonlinear derivative terms associated with the free energy equations into ones that can be treated by first order interpolation functions for high accuracy. The developed modeling methods for LC deformation are further employed to study display structures, such as 2D and 3D in-plane switching LC cells, and provides accurate results. Followed is the optical modeling using extended Jones matrix and beam propagation method to calculate the electro-optical performances of different devices, according to their amplitude modulation property or diffractive one. The developed methods are further taken to assist the understanding, development, and optimization of the display and photonic devices. For their application in the display area, sunlight readable transflective LCDs for mobile devices and the related optical films for wide viewing angle are developed and studied. New cell structure using vertically aligned liquid crystal mode is developed and studied to obtain a single cell gap, high light efficiency transflective LCD that can be driven by one gray scale control circuit for both transmissive and reflective modes. And employing an internal wire grid polarizer into a fringe field switching cell produces a single cell gap and wide viewing angle display with workable reflective mode under merely two linear polarizers. To solve the limited viewing angle of conventional circular polarizers, Poincaré sphere as an effective tool is taken to trace and understand the polarization change of the incident light throughout the whole LC system. This study further guides the design of high performance circular polarizers that can consist of purely uniaxial plates or a combination of uniaxial and biaxial plates. The developed circular polarizers greatly enhance the viewing angle of transflective LCDs. Especially, the circular polarizer design using a biaxial film can even provide comparable wide viewing angle performance for the same vertically aligned cell as it is used between merely two linear polarizers, while using circular polarizers can greatly boost the display brightness. As for the beam steering device modeling, the developed LC deformation method is taken to accurately calculate the associated LC director distribution in the spatial light modulator, while beam propagation method and Fourier transformation technique are combined to calculate the near and far fields from such devices. The modeling helps to better understand the origins and formations of the disclinations associated with the fringe fields, which further result in reduced steering efficiency and output asymmetric polarizations between positive and negative diffractions. Optimization in both voltage profile and driving methods is conducted to well tune the LC deformation under strong fringe fields and improve the light efficiency.
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Date Issued: 2007
Identifier: CFE0001908, ucf:47481
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001908

Title: DESIGN, MODELING, AND CONTROL OF THREE-PORT CONVERTERS FOR SOLAR POWER APPLICATIONS.
Creator: Reese, Justin, Batarseh, Issa, University of Central Florida
Abstract / Description: This paper describes the results of research into multi-port converter design and control, specifically a pair of three-port topologies based on the half-bridge and full-bridge topologies. These converters are capable of simultaneous and independent regulation of two out of their three ports, while the third port provides the power balance in the system. A dynamic model was developed for each topology to aid in testing and for designing the control loops. The models were then used to design...
Show moreThis paper describes the results of research into multi-port converter design and control, specifically a pair of three-port topologies based on the half-bridge and full-bridge topologies. These converters are capable of simultaneous and independent regulation of two out of their three ports, while the third port provides the power balance in the system. A dynamic model was developed for each topology to aid in testing and for designing the control loops. The models were then used to design the control structures, and the results were tested in Simulink. In addition, a basic outline of a system level architecture to control multiple converters working in parallel is presented. To improve the reliability of this system, output current sharing controls were also developed. Finally, one of the topologies is analyzed in detail in order to obtain a set of design equations that can be used to improve the efficiency, weight, and cost of the converter for a specific application.
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Date Issued: 2007
Identifier: CFE0001921, ucf:47487
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001921

Title: A HIGH-RESOLUTION STORM SURGE MODEL FOR THE PASCAGOULA REGION, MISSISSIPPI.
Creator: Takahashi, Naeko, Hagen, Scott, University of Central Florida
Abstract / Description: The city of Pascagoula and its coastal areas along the United States Gulf Coast have experienced many catastrophic hurricanes and were devastated by high storm surges caused by Hurricane Katrina (August 23 to 30, 2005). The National Hurricane Center reported high water marks exceeding 6 meters near the port of Pascagoula with a near 10-meter high water mark recorded near the Hurricane Katrina landfall location in Waveland, MS. Although the Pascagoula River is located 105 km east of the...
Show moreThe city of Pascagoula and its coastal areas along the United States Gulf Coast have experienced many catastrophic hurricanes and were devastated by high storm surges caused by Hurricane Katrina (August 23 to 30, 2005). The National Hurricane Center reported high water marks exceeding 6 meters near the port of Pascagoula with a near 10-meter high water mark recorded near the Hurricane Katrina landfall location in Waveland, MS. Although the Pascagoula River is located 105 km east of the landfall location of Hurricane Katrina, the area was devastated by storm surge-induced inundation because of its low elevation. Building on a preliminary finite element mesh for the Pascagoula River, the work presented herein is aimed at incorporating the marsh areas lying adjacent to the Lower Pascagoula and Escatawpa Rivers for the purpose of simulating the inland inundation which occurred during Hurricane Katrina. ADCIRC-2DDI (ADvanced CIRCulation Model for Shelves, Coasts and Estuaries, Two-Dimensional Depth Integrated) is employed as the hydrodynamic circulation code. The simulations performed in this study apply high-resolution winds and pressures over the 7-day period associated with Hurricane Katrina. The high resolution of the meteorological inputs to the problem coupled with the highly detailed description of the adjacent inundation areas will provide an appropriate modeling tool for studying storm surge dynamics within the Pascagoula River. All simulation results discussed herein are directed towards providing for a full accounting of the hydrodynamics within the Pascagoula River in support of ongoing flood/river forecasting efforts. In order to better understand the hydrodynamics within the Pascagoula River when driven by an extreme storm surge event, the following tasks were completed as a part of this study: 1) Develop an inlet-based floodplain DEM (Digital Elevation Model) for the Pascagoula River. The model employs topography up to the 1.5-meter contour extracted from the Southern Louisiana Gulf Coast Mesh (SL15 Mesh) developed by the Federal Emergency Management Agency (FEMA). 2) Incorporate the inlet-based floodplain model into the Western North Atlantic Tidal (WNAT) model domain, which consists of the Gulf of Mexico, the Caribbean Sea, and the entire portion of the North Atlantic Ocean found west of the 60 degree West meridian, in order to more fully account for the storm surge dynamics occurring within the Pascagoula River. This large-scale modeling approach will utilize high-resolution wind and pressure fields associated with Hurricane Katrina, so that storm surge hydrographs (elevation variance) at the open-ocean boundary locations associated with the localized domain can be adequately obtained. 3) Understand the importance of the various meteorological forcings that are attributable to the storm surge dynamics that are setup within the Pascagoula River. Different implementations of the two model domains (large-scale, including the WNAT model domain; localized, with its focus concentrated solely on the Pascagoula River) will involve the application of tides, storm surge hydrographs and meteorological forcing (winds and pressures) in isolation (i.e., as the single forcing mechanism) and collectively (i.e., together in combination). The following conclusions are drawn from the research presented in this thesis: 1) Incorporating the marsh areas into the preliminary in-bank mesh provides for significant improvement in the astronomic tide simulation; 2) the large-scale modeling approach (i.e., the localized floodplain mesh incorporated into the WNAT model domain) is shown to be most adequate towards simulating storm surge dynamics within the Pascagoula River. Further, we demonstrate the utility of the large-scale model domain towards providing storm surge hydrographs for the open-ocean boundary of the localized domain. Only when the localized domain is forced with the storm surge hydrograph (generated by the large-scale model domain) does it most adequately capture the full behavior of the storm surge. Finally, we discover that while the floodplain description up to the 1.5-m contour greatly improves the model response by allowing for the overtopping of the river banks, a true recreation of the water levels caused by Hurricane Katrina will require a floodplain description up to the 5-m contour.
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Date Issued: 2008
Identifier: CFE0002476, ucf:47719
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002476

Title: AN IMPROVED THERMOREGULATORY MODEL FOR COOLING GARMENT APPLICATIONS WITH TRANSIENT METABOLIC RATES.
Creator: Westin, Johan, Kapat, Jayanta, University of Central Florida
Abstract / Description: Current state-of-the-art thermoregulatory models do not predict body temperatures with the accuracies that are required for the development of automatic cooling control in liquid cooling garment (LCG) systems. Automatic cooling control would be beneficial in a variety of space, aviation, military, and industrial environments for optimizing cooling efficiency, for making LCGs as portable and practical as possible, for alleviating the individual from manual cooling control, and for improving...
Show moreCurrent state-of-the-art thermoregulatory models do not predict body temperatures with the accuracies that are required for the development of automatic cooling control in liquid cooling garment (LCG) systems. Automatic cooling control would be beneficial in a variety of space, aviation, military, and industrial environments for optimizing cooling efficiency, for making LCGs as portable and practical as possible, for alleviating the individual from manual cooling control, and for improving thermal comfort and cognitive performance. In this study, we adopt the Fiala thermoregulatory model, which has previously demonstrated state-of-the-art predictive abilities in air environments, for use in LCG environments. We validate the numerical formulation with analytical solutions to the bioheat equation, and find our model to be accurate and stable with a variety of different grid configurations. We then compare the thermoregulatory model's tissue temperature predictions with experimental data where individuals, equipped with an LCG, exercise according to a 700 W rectangular type activity schedule. The root mean square (RMS) deviation between the model response and the mean experimental group response is 0.16°C for the rectal temperature and 0.70°C for the mean skin temperature, which is within state-of-the-art variations. However, with a mean absolute body heat storage error (e_BHS_mean) of 9.7 W·h, the model fails to satisfy the ±6.5 W·h accuracy that is required for the automatic LCG cooling control development. In order to improve model predictions, we modify the blood flow dynamics of the thermoregulatory model. Instead of using step responses to changing requirements, we introduce exponential responses to the muscle blood flow and the vasoconstriction command. We find that such modifications have an insignificant effect on temperature predictions. However, a new vasoconstriction dependency, i.e. the rate of change of hypothalamus temperature weighted by the hypothalamus error signal (DThy·dThy/dt), proves to be an important signal that governs the thermoregulatory response during conditions of simultaneously increasing core and decreasing skin temperatures, which is a common scenario in LCG environments. With the new DThy·dThy/dt dependency in the vasoconstriction command, the e_BHS_mean for the exercise period is reduced by 59% (from 12.9 W·h to 5.2 W·h). Even though the new e_BHS_mean of 5.8 W·h for the total activity schedule is within the target accuracy of ±6.5 W·h, e_BHS fails to stay within the target accuracy during the entire activity schedule. With additional improvements to the central blood pool formulation, the LCG boundary condition, and the agreement between model set-points and actual experimental initial conditions, it seems possible to achieve the strict accuracy that is needed for automatic cooling control development.
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Date Issued: 2008
Identifier: CFE0002460, ucf:47707
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002460

Title: A MULTI-OBJECTIVE NO-REGRET DECISION MAKING MODEL WITH BAYESIAN LEARNING FOR AUTONOMOUS UNMANNED SYSTEMS.
Creator: Howard, Matthew, Qu, Zhihua, University of Central Florida
Abstract / Description: The development of a multi-objective decision making and learning model for the use in unmanned systems is the focus of this project. Starting with traditional game theory and psychological learning theories developed in the past, a new model for machine learning is developed. This model incorporates a no-regret decision making model with a Bayesian learning process which has the ability to adapt to errors found in preconceived costs associated with each objective. This learning ability is...
Show moreThe development of a multi-objective decision making and learning model for the use in unmanned systems is the focus of this project. Starting with traditional game theory and psychological learning theories developed in the past, a new model for machine learning is developed. This model incorporates a no-regret decision making model with a Bayesian learning process which has the ability to adapt to errors found in preconceived costs associated with each objective. This learning ability is what sets this model apart from many others. By creating a model based on previously developed human learning models, hundreds of years of experience in these fields can be applied to the recently developing field of machine learning. This also allows for operators to more comfortably adapt to the machine's learning process in order to better understand how to take advantage of its features. One of the main purposes of this system is to incorporate multiple objectives into a decision making process. This feature can better allow its users to clearly define objectives and prioritize these objectives allowing the system to calculate the best approach for completing the mission. For instance, if an operator is given objectives such as obstacle avoidance, safety, and limiting resource usage, the operator would traditionally be required to decide how to meet all of these objectives. The use of a multi-objective decision making process such as the one designed in this project, allows the operator to input the objectives and their priorities and receive an output of the calculated optimal compromise.
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Date Issued: 2008
Identifier: CFE0002453, ucf:47711
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002453

Title: PHASE-FIELD SIMULATION OF MICROSTRUCTURALDEVELOPMENT INDUCED BY INTERDIFFUSIONFLUXES UNDER MULTIPLE GRADIENTS.
Creator: Mohanty, Rashmi, Sohn, Yongho, University of Central Florida
Abstract / Description: The diffuse-interface phase-field model is a powerful method to simulate and predict mesoscale microstructure evolution in materials using fundamental properties of thermodynamics and kinetics. The objective of this dissertation is to develop phase-field model for simulation and prediction of interdiffusion behavior and evolution of microstructure in multi-phase binary and ternary systems under composition and/or temperature gradients. Simulations were carried out with emphasis on...
Show moreThe diffuse-interface phase-field model is a powerful method to simulate and predict mesoscale microstructure evolution in materials using fundamental properties of thermodynamics and kinetics. The objective of this dissertation is to develop phase-field model for simulation and prediction of interdiffusion behavior and evolution of microstructure in multi-phase binary and ternary systems under composition and/or temperature gradients. Simulations were carried out with emphasis on multicomponent diffusional interactions in single-phase system, and microstructure evolution in multiphase systems using thermodynamics and kinetics of real systems such as Ni-Al and Ni-Cr-Al. In addition, selected experimental studies were carried out to examine interdiffusion and microstructure evolution in Ni-Cr-Al and Fe-Ni-Al alloys at 1000C. Based on Onsager's formalism, a phase-field model was developed for the first time to simulate the diffusion process under an applied temperature gradient (i.e., thermotransport) in single- and two-phase binary alloys. Development of concentration profiles with uphill diffusion and the occurrence of zero-flux planes were studied in single-phase diffusion couples using a regular solution model for a hypothetical ternary system. Zero-flux plane for a component was observed to develop for diffusion couples at the composition that corresponds to the activity of that component in one of the terminal alloys. Morphological evolution of interphase boundary in solid-to-solid two-phase diffusion couples (fcc- vs. B2-) was examined in Ni-Cr-Al system with actual thermodynamic data and concentration dependent chemical mobility. With the instability introduced as a small initial compositional fluctuation at the interphase boundary, the evolution of the interface morphology was found to vary largely as a function of terminal alloys and related composition-dependent chemical mobility. In a binary Ni-Al system, multiphase diffusion couples of fcc- vs. L12-,  vs. and  vs.  were simulated with alloys of varying compositions and volume fractions of second phase (i.e., ). Chemical mobility as a function of composition was employed in the study with constant gradient energy coefficient, and their effects on the final interdiffusion microstructure was examined. Interdiffusion microstructure was characterized by the type of boundaries formed, i.e. Type 0, Type I, and Type II boundaries, following various experimental observations in literature and thermodynamic considerations. Volume fraction profiles of alloy phases present in the diffusion couples were measured to quantitatively analyze the formation or dissolution of phases across the boundaries. Kinetics of dissolution of  phase was found to be a function of interdiffusion coefficients that can vary with composition and temperature. The evolution of interdiffusion microstructures in ternary Ni-Cr-Al solid-to-solid diffusion couples containing fcc- and + (fcc+B2) alloys was studied using a 2D phase-field model. Alloys of varying compositions and volume fractions of the second phase () were used to simulate the dissolution kinetics of the  phase. Semi-implicit Fourier-spectral method was used to solve the governing equations with chemical mobility as a function of compositions. The simulation results showed that the rate of dissolution of the  phase (i.e., recession of  two-phase region) was dependent on the composition of the single-phase  alloy and the volume fraction of the  phase in the two-phase alloy of the couple. Higher Cr and Al content in the  alloy and higher volume fraction of  in the  alloy lower the rate of dissolution. Simulated results were found to be in good agreement with the experimental observations in ternary Ni-Cr-Al solid-to-solid diffusion couples containing  and  alloys. For the first time, a phase-field model was developed to simulate the diffusion process under an applied temperature gradient (i.e., thermotransport) in multiphase binary alloys. Starting from the phenomenological description of Onsager's formalism, the field kinetic equations are derived and applied to single-phase and two-phase binary system. Simulation results show that a concentration gradient develops due to preferential movement of atoms towards the cold and hot end of an initially homogeneous single-phase binary alloy subjected to a temperature gradient. The temperature gradient causes the redistribution of both constituents and phases in the two-phase binary alloy. The direction of movement of elements depends on their atomic mobility and heat of transport values.
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Date Issued: 2009
Identifier: CFE0002515, ucf:47658
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002515

Title: BENCHMARK STUDIES FOR STRUCTURAL HEALTH MONITORING USING ANALYTICAL AND EXPERIMENTAL MODELS.
Creator: Burkett, Jason, Catbas, Necati, University of Central Florida
Abstract / Description: The latest bridge inventory report for the United States indicates that 25% of the highway bridges are structurally deficient or functionally obsolete. With such a large number of bridges in this condition, safety and serviceability concerns become increasingly relevant along with the associated increase in user costs and delays. Biennial inspections have proven subjective and need to be coupled with standardized non-destructive testing methods to accurately assess a bridge's condition for...
Show moreThe latest bridge inventory report for the United States indicates that 25% of the highway bridges are structurally deficient or functionally obsolete. With such a large number of bridges in this condition, safety and serviceability concerns become increasingly relevant along with the associated increase in user costs and delays. Biennial inspections have proven subjective and need to be coupled with standardized non-destructive testing methods to accurately assess a bridge's condition for decision making purposes. Structural health monitoring is typically used to track and evaluate performance, symptoms of operational incidents, anomalies due to deterioration and damage during regular operation as well as after an extreme event. Dynamic testing and analysis are concepts widely used for health monitoring of existing structures. Successful health monitoring applications on real structures can be achieved by integrating experimental, analytical and information technologies on real life, operating structures. Real-life investigations must be backed up by laboratory benchmark studies. In addition, laboratory benchmark studies are critical for validating theory, concepts, and new technologies as well as creating a collaborative environment between different researchers. To implement structural health monitoring methods and technologies, a physical bridge model was developed in the UCF structures laboratory as part of this thesis research. In this study, the development and testing of the bridge model are discussed after a literature review of physical models. Different aspects of model development, with respect to the physical bridge model are outlined in terms of design considerations, instrumentation, finite element modeling, and simulating damage scenarios. Examples of promising damage detection methods were evaluated for common damage scenarios simulated on the numerical and physical models. These promising damage indices were applied and directly compared for the same experimental and numerical tests. To assess the simulated damage, indices such as modal flexibility and curvature were applied using mechanics and structural dynamics theory. Damage indices based on modal flexibility were observed to be promising as one of the primary indicators of damage that can be monitored over the service life of a structure. Finally, this thesis study will serve an international effort that has been initiated to explore bridge health monitoring methodologies under the auspices of International Association for Bridge Maintenance and Safety (IABMAS). The data generated in this thesis research will be made available to researchers as well as practitioners in the broad field of structural health monitoring through several national and international societies, associations and committees such as American Society of Civil Engineers (ASCE) Dynamics Committee, and the newly formed ASCE Structural Health Monitoring and Control Committee.
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Date Issued: 2005
Identifier: CFE0000636, ucf:46514
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000636

Title: LIFE EVENT PERCEPTION:A STRUCTURAL EQUATION MODELING APPROACH TO THE ANTECEDENTS OF THE LIFE STRESS RESPONSE.
Creator: Myers, Christopher, Bowers, Clint, University of Central Florida
Abstract / Description: It has been often argued that life events have an impact on our physical and psychological well-being. In general, research supports this connection between life events and general health, though some argue that simply experiencing life events has a measurable and predictable impact our health, while others contend that this effect is mediated by the appraisal process. Further, research has identified a number of different factors (hypothetically stratified into pre-existing beliefs, external...
Show moreIt has been often argued that life events have an impact on our physical and psychological well-being. In general, research supports this connection between life events and general health, though some argue that simply experiencing life events has a measurable and predictable impact our health, while others contend that this effect is mediated by the appraisal process. Further, research has identified a number of different factors (hypothetically stratified into pre-existing beliefs, external resources and demands, and behavioral activation and coping strategies) that may influence appraisal and general health. The current study attempts to integrate these findings by testing structural models of the relationship between life events, life stress, and general health while considering the appraisal process and other potential moderators of appraisal and general health. University students (N=204) were tested using 17 assessment measures representing 7 latent constructs of Life Events, Life Stress, Appraisal, General Health, Beliefs, External, and Activation. Results of the measurement models required model respecification to combine Appraisal and Beliefs into one construct and External and Activation into another construct, resulting in a five-factor hypothetical structural model. The resulting empirical structural model is a partially-mediated model that suggests that appraisal and pre-existing beliefs influence the relationship between life events and life stress, and that life events significantly impact measured life stress. The empirical model also indicates that general health is significantly impacted by life stress, as well as behavioral activation and external resources and demands. Practical implications of the findings and recommendations for further research were discussed.
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Date Issued: 2005
Identifier: CFE0000628, ucf:46519
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000628

Title: HOW DOES THE USE OF PICTURE BOOKS DURING INSTRUCTION IMPROVE STUDENT WORD CHOICE IN WRITING?.
Creator: McAdams, Laurie, Camp, Donna, University of Central Florida
Abstract / Description: The purpose of my research was to determine how the use of picture books during instruction would improve student word choice in writing. Donald Graves (2003), a renowned researcher in the teaching of writing, states, "All children need . . . to be surrounded with poetry, stories, information books, biography, science and history, imaginative and factual books." Graves' research presents successful classroom instruction when teachers incorporate literature as a fundamental part of their...
Show moreThe purpose of my research was to determine how the use of picture books during instruction would improve student word choice in writing. Donald Graves (2003), a renowned researcher in the teaching of writing, states, "All children need . . . to be surrounded with poetry, stories, information books, biography, science and history, imaginative and factual books." Graves' research presents successful classroom instruction when teachers incorporate literature as a fundamental part of their reading and writing instruction. Likewise, Susan Anderson McElveen and Connie Campbell Dierking (2000) conducted a study with their students using picture books as "precise examples" to teach writing. Their analysis of data showed that using children's literature, or picture books, served as a "bridge that linked the target skill with the reason for thinking, speaking, and writing like a writer" with their students. The subjects of my study were my fourth-grade students. I obtained data for this study from student writing samples, anecdotal records of my students, my daily reflections, class discussions, debriefings, and writing activities. I assessed students' writing samples using criteria for assessing word choice in the 6-Point Writing Guide in Vicki Spandel's (2005) Creating Young Writers. This study found that the majority of my students demonstrated improved word choice in their writing. Limitations of this study are discussed, as well as implications for future use of picture books during instruction.
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Date Issued: 2005
Identifier: CFE0000592, ucf:46473
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000592

Title: A THEORETICAL APPROACH TO ASSESSING ANNUAL ENERGY BALANCE IN GRAY WHALES (ESCHRICHTIUS ROBUSTUS).
Creator: Greenwald, Nathalie, Worthy, Graham, University of Central Florida
Abstract / Description: While direct measurements of energetic demands are nearly impossible to collect on large cetaceans, comprehensive bioenergetic models can give insights on such parameters by combining physiological and ecological knowledge. This model was developed to estimate necessary food intake of gray whales, Eschrichtius robustus, of the Eastern North Pacific stock. Field Metabolic Rates (FMR) for gray whales were first estimated based on various assumptions (e.g. volumetric representation of gray...
Show moreWhile direct measurements of energetic demands are nearly impossible to collect on large cetaceans, comprehensive bioenergetic models can give insights on such parameters by combining physiological and ecological knowledge. This model was developed to estimate necessary food intake of gray whales, Eschrichtius robustus, of the Eastern North Pacific stock. Field Metabolic Rates (FMR) for gray whales were first estimated based on various assumptions (e.g. volumetric representation of gray whales, extent of their feeding season, and blubber depth distribution) using morphometric data, energetic costs, and food assimilation according to age and gender specific requirements. Food intake rates for gray whales of varying maturity and gender were then estimated based on FMR and caloric value of prey and compared to food intake rates of previous studies. Monte Carlo simulations and sensitivity analysis were performed to assess the model's predictions compared to observed field data from previous studies. Predicted average food intakes for adult male, pregnant/ lactating female, and immature whales were 475 ± 300, 525 ± 300 and 600 ± 300 kg d-1, respectively. Estimated blubber depths resulting from these food intakes were comparable to field data obtained from whaling data. Sensitivity analysis indicated food intake, from all parameters, as having the highest impact on the percent change in ending mass from a simulation. These food intake estimates are similar to those found in a previous study and fall within the range of food intake per body mass observed in other species of cetaceans. Though thermoregulation can be a factor in some cetaceans, it appears not to be an additional cost for gray whales as the present model's predicted lower critical temperatures for the whales (TLC) were below ambient temperatures. With temperatures increasing in the Bering Sea, the main prey of gray whales, ampeliscid amphipods, could be adversely affected, possibly resulting in increased food shortages leading to a surge in gray whale strandings.
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Date Issued: 2005
Identifier: CFE0000560, ucf:46442
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000560

Title: NITRIFICATION INVESTIGATION AND MODELING IN THE CHLORAMINATED DRINKING WATER DISTRIBUTION SYSTEM.
Creator: Liu, Suibing, Taylor, James, University of Central Florida
Abstract / Description: This dissertation consists of five papers concerning nitrification in chloraminated drinking water distribution systems in a one and a half year field study. Seven finished waters were produced from different treatment processes and distributed to eighteen pilot distribution systems (PDSs) that were made pipes taken from actual distribution systems. Unlined cast iron (UCI), galvanized steel (G), lined cast iron (LCI), and PVC pipes were used to build the PDSs. All finished waters were...
Show moreThis dissertation consists of five papers concerning nitrification in chloraminated drinking water distribution systems in a one and a half year field study. Seven finished waters were produced from different treatment processes and distributed to eighteen pilot distribution systems (PDSs) that were made pipes taken from actual distribution systems. Unlined cast iron (UCI), galvanized steel (G), lined cast iron (LCI), and PVC pipes were used to build the PDSs. All finished waters were stabilized and chloraminated before entering the PDSs. This dissertation consists of five major parts.(1) System variations of nitrates, nitrites, DO, pH, alkalinity, temperature, chloramine residuals and hydraulic residence times (HRT) during biological nitrification are interrelated and discussed relative to nitrification, which demonstrated Stoichiometric relationships associated with conventional biochemical nitrification reactions. Ammonia is always released when chloramines are used for residual maintenance in drinking water distribution systems, which practically insures the occurrence of biological nitrification to some degree. Biological nitrification was initiated by a loss of chloramine residual brought about by increasing temperatures at a five day HRT, which was accompanied by DO loss and slightly decreased pH. Ammonia increased due to chloramine decomposition and then decreased as nitrification began. Nitrites and nitrates increased initially with time after the chloramine residual was lost but decreased if denitrification began. Dissolved oxygen limited nitrifier growth and nitrification. No significant alkalinity variation was observed during nitrification. Residual and nitrites are key parameters for monitoring nitrification in drinking water distribution systems.(2) Using Monod kinetics, a steady state plug-flow kinetics model was developed to describe the variations of ammonia, nitrite and nitrate-N concentrations in a chloraminated distribution system. Active AOB and NOB biomass in the distribution system was determined using predictive equations within the model. The kinetic model used numerical analysis and was solved by C language to predict ammonia, nitrite, nitrate variation.(3) Nitrification control strategies were investigated during an unexpected episode and controlled study in a field study. Once nitrification began, increasing chloramine dose from 4.0 to 4.5 mg/L as Cl2 and Cl2:N ratio from 4/1 to 5/1 did not stop nitrification. Nitrification was significantly reduced but not stopped, when the distribution system hydraulic retention time was decreased from 5 to 2 days. A free chlorine burn for one week at 5 mg/L Cl2 stopped nitrification. In a controlled nitrification study, nitrification increased with increasing free ammonia and Cl2:N ratios less than 5. Flushing with increased chloramine concentration reduced nitrification, but varying flush frequency from 1 to 2 weeks had no effect on nitrification.(4) HPC variations in a chloraminated drinking water distribution system were investigated. Results showed average residual and temperature were the only water quality variables shown to affect HPC change at a five day distribution system hydraulic residence time was five days. Once nitrification began, HPC change was correlated to HRT, average residual and generated nitrite-N in the distribution system. (5) Biostability was assessed for water treatment processes and distribution system pipe by AOCs, BDOCs, and HPCs of the bulk water, and by PEPAs of the attached biofilms. All membrane finished waters were more likely to be biologically stable as indicated by lower AOCs. RO produced the lowest AOC. The order of biofilm growth by pipe material was UCI > G > LCI > PVC. Biostability decreased as temperature increased.
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Date Issued: 2004
Identifier: CFE0000039, ucf:46151
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000039

Title: TECHNIQUES FOR ASSESSING AND IMPROVING PERFORMANCE IN NAVIGATION AND WAYFINDING USING MOBILE AUGMENTED REALITY.
Creator: Goldiez, Brian, Hancock, Peter, University of Central Florida
Abstract / Description: Augmented reality is a field of technology in which the real world is overlaid with additional information from a computer generated display. Enhancements to augmented reality technology presently support limited mobility which is expected to increase in the future to provide much greater real world functionality. This work reports on a set of experiments that investigate performance in search and rescue navigating tasks using augmented reality. Augmentation consisted of a spatially and...
Show moreAugmented reality is a field of technology in which the real world is overlaid with additional information from a computer generated display. Enhancements to augmented reality technology presently support limited mobility which is expected to increase in the future to provide much greater real world functionality. This work reports on a set of experiments that investigate performance in search and rescue navigating tasks using augmented reality. Augmentation consisted of a spatially and temporally registered map of a maze that was overlaid onto a real world maze. Participants were required to traverse the maze, answer spatially oriented questions in the maze, acquire a target object, and exit. Pre and post hoc questionnaires were administered. Time and accuracy data from one hundred twenty participants were collected across six treatments. The between subject treatments, which had an equal number of male and female participants, were a control condition with only a compass, a control condition with a paper map available prior to maze traversal and four experimental conditions consisting of combinations of egocentric and exocentric maps, and a continuously on and on demand map display. Data collected from each participant consisted of time to traverse the maze, percent of the maze covered, estimations of euclidian distance and direction, estimations of cardinal direction, and spatial recall. Data was also collected via pre and post hoc questionnaires. Results indicate that best performance with respect to time was in the control condition with a map. The small size of the maze could have facilitated this result through route memorization. Augmented reality can offer enhancement to performance as navigational tasks become more complex and saturate working memory. Augmented reality showed best performance in accuracy by facilitating participants' coverage of the maze. Exocentric maps generally exhibited better performance than egocentric maps. On demand displays also generally resulted in better performance than continuously on displays. Gender differences also were evident with males exhibiting better performance than females. Participants reporting an initial tendency to not rotate maps exhibited better performance than those reporting a tendency to rotate maps. Enhancements being made to augmented reality and related technologies will result in more features, improved form factor for users, and improved performance in the future. Guidelines provided in this work seek to ensure augmented reality systems continue to progress in enhancing performance
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Date Issued: 2004
Identifier: CFE0000177, ucf:46157
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000177

Title: STUDY OF NANOSCALE CMOS DEVICE AND CIRCUIT RELIABILITY.
Creator: Yu, Chuanzhao, Yuan, Jiann S., University of Central Florida
Abstract / Description: The development of semiconductor technology has led to the significant scaling of the transistor dimensions -The transistor gate length drops down to tens of nanometers and the gate oxide thickness to 1 nm. In the future several years, the deep submicron devices will dominate the semiconductor industry for the high transistor density and the corresponding performance enhancement. For these devices, the reliability issues are the first concern for the commercialization. The major reliability...
Show moreThe development of semiconductor technology has led to the significant scaling of the transistor dimensions -The transistor gate length drops down to tens of nanometers and the gate oxide thickness to 1 nm. In the future several years, the deep submicron devices will dominate the semiconductor industry for the high transistor density and the corresponding performance enhancement. For these devices, the reliability issues are the first concern for the commercialization. The major reliability issues caused by voltage and/or temperature stress are gate oxide breakdown (BD), hot carrier effects (HCs), and negative bias temperature instability (NBTI). They become even more important for the nanoscale CMOS devices, because of the high electrical field due to the small device size and high temperature due to the high transistor densities and high-speed performances. This dissertation focuses on the study of voltage and temperature stress-induced reliability issues in nanoscale CMOS devices and circuits. The physical mechanisms for BD, HCs, and NBTI have been presented. A practical and accurate equivalent circuit model for nanoscale devices was employed to simulate the RF performance degradation in circuit level. The parameter measurement and model extraction have been addressed. Furthermore, a methodology was developed to predict the HC, TDDB, and NBTI effects on the RF circuits with the nanoscale CMOS. It provides guidance for the reliability considerations of the RF circuit design. The BD, HC, and NBTI effects on digital gates and RF building blocks with the nanoscale devices – low noise amplifier, oscillator, mixer, and power amplifier, have been investigated systematically. The contributions of this dissertation include: It provides a thorough study of the reliability issues caused by voltage and/or temperature stresses on nanoscale devices – from device level to circuit level; The more real voltage stress case – high frequency (900 MHz) dynamic stress, has been first explored and compared with the traditional DC stress; A simple and practical analytical method to predict RF performance degradation due to voltage stress in the nanoscale devices and RF circuits was given based on the normalized parameter degradations in device models. It provides a quick way for the designers to evaluate the performance degradations; Measurement and model extraction technologies, special for the nanoscale MOSFETs with ultra-thin, ultra-leaky gate oxide, were addressed and employed for the model establishments; Using the present existing computer-aided design tools (Cadence, Agilent ADS) with the developed models for performance degradation evaluation due to voltage or/and temperature stress by simulations provides a potential way that industry could use to save tens of millions of dollars annually in testing costs. The world now stands at the threshold of the age of nanotechnology, and scientists and engineers have been exploring here for years. The reliability is the first challenge for the commercialization of the nanoscale CMOS devices, which will be further downscaling into several tens or ten nanometers. The reliability is no longer the post-design evaluation, but the pre-design consideration. The successful and fruitful results of this dissertation, from device level to circuit level, provide not only an insight on how the voltage and/or temperature stress effects on the performances, but also methods and guidance for the designers to achieve more reliable circuits with nanoscale MOSFETs in the future.
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Date Issued: 2006
Identifier: CFE0000948, ucf:46746
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000948

Title: SESSION-BASED INTRUSION DETECTION SYSTEM TO MAP ANOMALOUS NETWORK TRAFFIC.
Creator: Caulkins, Bruce, Wang, Morgan, University of Central Florida
Abstract / Description: Computer crime is a large problem (CSI, 2004; Kabay, 2001a; Kabay, 2001b). Security managers have a variety of tools at their disposal – firewalls, Intrusion Detection Systems (IDSs), encryption, authentication, and other hardware and software solutions to combat computer crime. Many IDS variants exist which allow security managers and engineers to identify attack network packets primarily through the use of signature detection; i.e., the IDS recognizes attack packets due to their well...
Show moreComputer crime is a large problem (CSI, 2004; Kabay, 2001a; Kabay, 2001b). Security managers have a variety of tools at their disposal – firewalls, Intrusion Detection Systems (IDSs), encryption, authentication, and other hardware and software solutions to combat computer crime. Many IDS variants exist which allow security managers and engineers to identify attack network packets primarily through the use of signature detection; i.e., the IDS recognizes attack packets due to their well-known "fingerprints" or signatures as those packets cross the network's gateway threshold. On the other hand, anomaly-based ID systems determine what is normal traffic within a network and reports abnormal traffic behavior. This paper will describe a methodology towards developing a more-robust Intrusion Detection System through the use of data-mining techniques and anomaly detection. These data-mining techniques will dynamically model what a normal network should look like and reduce the false positive and false negative alarm rates in the process. We will use classification-tree techniques to accurately predict probable attack sessions. Overall, our goal is to model network traffic into network sessions and identify those network sessions that have a high-probability of being an attack and can be labeled as a "suspect session." Subsequently, we will use these techniques inclusive of signature detection methods, as they will be used in concert with known signatures and patterns in order to present a better model for detection and protection of networks and systems.
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Date Issued: 2005
Identifier: CFE0000906, ucf:46762
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000906

Title: APPLYING LOG-LINEAR MODELS AND GIS TO STUDY THE SAFETY OF PEDESTRIANS AND BICYCLISTS : A CASE STUDY OF ORANGE COUNTY SCHOOL CHILDREN.
Creator: Chundi, Sai Srinivas, Mohamed, Abdel Aty, University of Central Florida
Abstract / Description: Abstract Pedestrian /bicycle safety of school children has been a growing menace that has been attracting attention from transportation professionals, school boards, media and the community all over the country. As such there has been a necessity to identify critical variables and assess their importance in pedestrian/bicycle crashes occurring in and around school zones. The current study is an endeavor in this direction. The literature review identified some studies that were conducted on...
Show moreAbstract Pedestrian /bicycle safety of school children has been a growing menace that has been attracting attention from transportation professionals, school boards, media and the community all over the country. As such there has been a necessity to identify critical variables and assess their importance in pedestrian/bicycle crashes occurring in and around school zones. The current study is an endeavor in this direction. The literature review identified some studies that were conducted on school zone safety related to pedestrian/bicyclist crashes. Most of the studies pertained to crashes with all age groups. There have been few studies with emphasis only on school aged children. In this study we focus on pedestrian age group (4 to 18 years), the time of the day when the school children are expected to be commuting (6:30 AM to 10:00 AM and 1:00 PM to 5:00.PM), the day of week (Monday through Friday) and the days when the school is opened (January 6th to May 31st and August 6th to December 21st). Geographical Information Systems was used to locate buffer zones around schools with higher crash incidence rates. The use of log-linear analysis has culminated in explaining the relationship between various variables and crash incidence or crash frequency Crash data for this study was obtained in the form of crash database and GIS maps from the Department of Highway Safety and Motor Vehicles and the Orange County School Board respectively. Crash reports were downloaded from the CAR database of the FDOT mainframe website. The crash data was related to the GIS maps to visually depict the proximity of crashes to the school zones and thus identified risky schools and school districts. It was concluded from the spatial analysis that the incidence of crashes was higher at middle schools. In the log-linear analysis different models were i tested to explain the effects of driver characteristics, geometric characteristics and pedestrian characteristics on the crash frequency. It was found that driver age, number of lanes, median type, pedestrian age and speed limit are the critical variables in explaining crash frequency. By examining the levels of the variables that were significantly involved in the crashes we would get an insight on ways to explain and control pedestrian/bicyclists crashes at school zones. It is hoped that this thesis would make an active contribution in improving the safety of bicyclists and pedestrians in and around school zones and make the schools much safer for the children.
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Date Issued: 2005
Identifier: CFE0000885, ucf:46643
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000885

Title: EMPIRICAL MODELING OF A MARIJUANA EXPECTANCY MEMORY NETWORK IN CHILDREN AS A FUNCTION OF AGE AND MARIJUANA USE.
Creator: Alfonso, Jacqueline, Dunn, Michael, University of Central Florida
Abstract / Description: The present investigation modeled the expectancy memory organization and likely memory activation patterns of marijuana expectancies of children across age and marijuana use. The first phase of the study surveyed 142 children to obtain their first associate to marijuana use. From their responses, the Marijuana Expectancy Inventory for Children and Adolescents (MEICA) was developed. The second phase of the study administered the MEICA to a second sample of 392 children to model marijuana...
Show moreThe present investigation modeled the expectancy memory organization and likely memory activation patterns of marijuana expectancies of children across age and marijuana use. The first phase of the study surveyed 142 children to obtain their first associate to marijuana use. From their responses, the Marijuana Expectancy Inventory for Children and Adolescents (MEICA) was developed. The second phase of the study administered the MEICA to a second sample of 392 children to model marijuana expectancy organization and probable memory activation paths of marijuana users versus never-users. Results indicated that irrespective of age, adolescents who have used marijuana tend to emphasize positive-negative effects, whereas adolescents who have never used marijuana tend to emphasize psychological-physiological effects. Memory activation patterns also differed by marijuana use history such that users are more likely to begin their paths with short-term positive effects of marijuana, versus non-users who access long-term cognitive and physiological effects with more likelihood. This study is the first to examine specific marijuana outcome expectancies of children and adolescents as they relate to marijuana-using behavior. Implications for marijuana prevention and intervention programs, future research, and limitations of the current investigation are discussed.
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Date Issued: 2005
Identifier: CFE0000897, ucf:46629
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000897

Title: CREATING MODELS OF INTERNET BACKGROUND TRAFFIC SUITABLE FOR USE IN EVALUATING NETWORK INTRUSION DETECTION SYSTEMS.
Creator: LUO, SONG, Marin, Gerald, University of Central Florida
Abstract / Description: This dissertation addresses Internet background traffic generation and network intrusion detection. It is organized in two parts. Part one introduces a method to model realistic Internet background traffic and demonstrates how the models are used both in a simulation environment and in a lab environment. Part two introduces two different NID (Network Intrusion Detection) techniques and evaluates them using the modeled background traffic. To demonstrate the approach we modeled five major...
Show moreThis dissertation addresses Internet background traffic generation and network intrusion detection. It is organized in two parts. Part one introduces a method to model realistic Internet background traffic and demonstrates how the models are used both in a simulation environment and in a lab environment. Part two introduces two different NID (Network Intrusion Detection) techniques and evaluates them using the modeled background traffic. To demonstrate the approach we modeled five major application layer protocols: HTTP, FTP, SSH, SMTP and POP3. The model of each protocol includes an empirical probability distribution plus estimates of application-specific parameters. Due to the complexity of the traffic, hybrid distributions (called mixture distributions) were sometimes required. The traffic models are demonstrated in two environments: NS-2 (a simulator) and HONEST (a lab environment). The simulation results are compared against the original captured data sets. Users of HONEST have the option of adding network attacks to the background. The dissertation also introduces two new template-based techniques for network intrusion detection. One is based on a template of autocorrelations of the investigated traffic, while the other uses a template of correlation integrals. Detection experiments have been performed on real traffic and attacks; the results show that the two techniques can achieve high detection probability and low false alarm in certain instances.
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Date Issued: 2005
Identifier: CFE0000852, ucf:46667
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000852

Title: DESIGN AND OPTIMIZATION OF NANO-OPTICAL ELEMENTS BY COUPLING FABRICATION TO OPTICAL BEHAVIOR.
Creator: Rumpf, Raymond, Johnson, Eric, University of Central Florida
Abstract / Description: Photonic crystals and nanophotonics have received a great deal of attention over the last decade, largely due to improved numerical modeling and advances in fabrication technologies. To this day, fabrication and optical behavior remain decoupled during the design phase and numerous assumptions are made about "perfect" geometry. As research moves from theory to real devices, predicting device behavior based on realistic geometry becomes critical. In this dissertation, a set of numerical tools...
Show morePhotonic crystals and nanophotonics have received a great deal of attention over the last decade, largely due to improved numerical modeling and advances in fabrication technologies. To this day, fabrication and optical behavior remain decoupled during the design phase and numerous assumptions are made about "perfect" geometry. As research moves from theory to real devices, predicting device behavior based on realistic geometry becomes critical. In this dissertation, a set of numerical tools was developed to model micro and nano fabrication processes. They were combined with equally capable tools to model optical performance of the simulated structures. Using these tools, it was predicted and demonstrated that 3D nanostructures may be formed on a standard mask aligner. A space-variant photonic crystal filter was designed and optimized based on a simple fabrication method of etching holes through hetero-structured substrates. It was found that hole taper limited their optical performance and a method was developed to compensate. A method was developed to tune the spectral response of guided-mode resonance filters at the time of fabrication using models of etching and deposition. Autocloning was modeled and shown that it could be used to form extremely high aspect ratio structures to improve performance of form-birefringent devices. Finally, the numerical tools were applied to metallic photonic crystal devices.
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Date Issued: 2006
Identifier: CFE0001159, ucf:46849
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001159

Title: MATHEMATICAL MODELING OF SMALLPOX WITHOPTIMAL INTERVENTION POLICY.
Creator: LAWOT, NIWAS, ROLLINS, DAVID, University of Central Florida
Abstract / Description: In this work, two differential equation models for smallpox are numerically solved to find the optimal intervention policy. In each model we look for the range of values of the parameters that give rise to the worst case scenarios. Since the scale of an epidemic is determined by the number of people infected, and eventually dead, as a result of infection, we attempt to quantify the scale of the epidemic and recommend the optimum intervention policy. In the first case study, we mimic a densely...
Show moreIn this work, two differential equation models for smallpox are numerically solved to find the optimal intervention policy. In each model we look for the range of values of the parameters that give rise to the worst case scenarios. Since the scale of an epidemic is determined by the number of people infected, and eventually dead, as a result of infection, we attempt to quantify the scale of the epidemic and recommend the optimum intervention policy. In the first case study, we mimic a densely populated city with comparatively big tourist population, and heavily used mass transportation system. A mathematical model for the transmission of smallpox is formulated, and numerically solved. In the second case study, we incorporate five different stages of infection: (1) susceptible (2) infected but asymptomatic, non infectious, and vaccine-sensitive; (3) infected but asymptomatic, noninfectious, and vaccine-in-sensitive; (4) infected but asymptomatic, and infectious; and (5) symptomatic and isolated. Exponential probability distribution is used for modeling this case. We compare outcomes of mass vaccination and trace vaccination on the final size of the epidemic.
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Date Issued: 2006
Identifier: CFE0001193, ucf:46848
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001193

Title: THE EFFECTS OF THE 5E LEARNING CYCLE MODEL ON STUDENTS' UNDERSTANDING OF FORCE AND MOTION CONCEPTS.
Creator: Campbell, Meghann, Sweeney, Aldrin, University of Central Florida
Abstract / Description: As advocated by the National Research Council [NRC] (1996) and the American Association for the Advancement of Science [AAAS] (1989), a change in the manner in which science is taught must be recognized at a national level and also embraced at a level that is reflected in every science teacher's classroom. With these ideas set forth as a guide for change,this study investigated the fifth grade students' understanding of force and motion concepts as they engaged in inquiry-based science...
Show moreAs advocated by the National Research Council [NRC] (1996) and the American Association for the Advancement of Science [AAAS] (1989), a change in the manner in which science is taught must be recognized at a national level and also embraced at a level that is reflected in every science teacher's classroom. With these ideas set forth as a guide for change,this study investigated the fifth grade students' understanding of force and motion concepts as they engaged in inquiry-based science investigations through the use of the 5E Learning Cycle. The researcher's journey through this process was also a focus of the study. Initial data were provided by a pretest indicating students' understanding of force and motion concepts. Four times weekly for a period of 14 weeks, students participated in investigations related to force and motion concepts. Their subsequent understanding of these concepts and their ability to generalize their understandings was evaluated via a posttest. Additionally, a review of lab activity sheets, other classroom-based assessments, and filmed interviews allowed for the triangulation of pertinent data necessary to draw conclusions from the study. Findings showed that student knowledge of force and motion concepts did increase although their understanding as demonstrated on paper lacked completeness versus understanding in an interview setting. Survey results also showed that after the study students believed they did not learn science best via textbook-based instruction.
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Date Issued: 2006
Identifier: CFE0001007, ucf:46831
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001007

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