View All Items
(41 - 60 of 113)
Pages
- Title
- FINITE ELEMENT ANALYSIS OF LEFT-HANDED WAVEGUIDES.
- Creator
-
Vellakkinar Balasubramaniam, Satish, Wu, Thomas X, University of Central Florida
- Abstract / Description
-
In this work, waveguides with simultaneous negative dielectric permittivity and magnetic permeability, otherwise known as left-handed waveguides, are investigated. An approach of formulating and solving an eigenvalue problem with finite element method resulting in the dispersion relation of the waveguides is adopted in the analysis. Detailed methodology of one-dimensional scalar and two-dimensional vector finite element formulation for the analysis of grounded slab and arbitrary shaped...
Show moreIn this work, waveguides with simultaneous negative dielectric permittivity and magnetic permeability, otherwise known as left-handed waveguides, are investigated. An approach of formulating and solving an eigenvalue problem with finite element method resulting in the dispersion relation of the waveguides is adopted in the analysis. Detailed methodology of one-dimensional scalar and two-dimensional vector finite element formulation for the analysis of grounded slab and arbitrary shaped waveguides is presented. Based on the analysis, for waveguides with conventional media, excellent agreement of results is observed between the finite element approach and the traditional approach. The method is then applied to analyze left-handed waveguides and anomalous dispersion of modes is found. The discontinuity structure of a left-handed waveguide sandwiched between two conventional dielectric slab waveguides is analyzed using mode matching technique and the results are discussed based on the inherent nature of the materials. The scattering characteristics of a parallel plate waveguide partially filled with left-handed and conventional media are also analyzed using finite element method with eigenfunction expansion technique.
Show less - Date Issued
- 2004
- Identifier
- CFE0000296, ucf:46208
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000296
- Title
- EFFECTS OF A MODIFIED JUDO PROGRAM ON PSYCHOSOCIAL FACTORS IN TYPICALLY DEVELOPING AND CHILDREN WITH AUTISM SPECTRUM DISORDER: A MIXED-METHODS STUDY.
- Creator
-
Tomey, Keanu L., Garcia, Jeanette M., Fukuda, David H., University of Central Florida
- Abstract / Description
-
PURPOSE: The purpose of this study was to examine the effect of a modified judo training program on psychosocial health in both typically developing (TD) and children with Autism Spectrum Disorder (ASD) using a mixed-methods approach. METHODS: The sample consisted of 5 children with ASD and 5 TD children (age=8-11yrs) who participated in 10 sessions of a modified judo program during their typical physical education time for school. Psychosocial factors (enjoyment, perceived competence,...
Show morePURPOSE: The purpose of this study was to examine the effect of a modified judo training program on psychosocial health in both typically developing (TD) and children with Autism Spectrum Disorder (ASD) using a mixed-methods approach. METHODS: The sample consisted of 5 children with ASD and 5 TD children (age=8-11yrs) who participated in 10 sessions of a modified judo program during their typical physical education time for school. Psychosocial factors (enjoyment, perceived competence, benefits of PA) were assessed at baseline and post intervention, with completion of all measures dependent upon the level of comfort expressed by the participant. At the end of the program, children took part in focus group discussions centered around their experience with the program, while key school staff participated in semi-structured interviews based on their observations of the program. All focus group discussions and interviews were audio-recorded and transcribed verbatim. RESULTS: Quantitative results for pre and post psychosocial measures showed no significant differences existed between PA self-efficacy (p=.99), PA enjoyment (p=.6), and barriers to PA (p=.27). Qualitative results revealed that the majority of the participants found the program to be enjoyable, with partner centered activities being particularly fun. Suggestions for improvement included increasing the duration and frequency of the judo classes. All children reported a desire to continue participating in the judo classes. Findings from staff interviews indicated that school staff observed improvements in psychosocial health and behavior both immediately following a judo class, and throughout the intervention period. Increased self-confidence was mentioned by all participating school staff members. CONCLUSION: Despite the lack of significant quantitative findings, psychosocial benefits were observed in both TD children and children with ASD, with all participants reporting their desire to continue with the program. Future studies should examine the psychosocial benefits in a judo-training program in larger sample of children over longer durations.
Show less - Date Issued
- 2017
- Identifier
- CFH2000252, ucf:46017
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000252
- Title
- ANALYSIS, MODELING, AND SIMULATION OF THE TIDES IN THE LOXAHATCHEE RIVER ESTUARY (SOUTHEASTERN FLORIDA).
- Creator
-
Bacopoulos, Peter, Hagen, Scott, University of Central Florida
- Abstract / Description
-
Recent cooperative efforts between the University of Central Florida, the Florida Department of Environmental Protection, and the South Florida Water Management District explore the development of a two-dimensional, depth-integrated tidal model for the Loxahatchee River estuary (Southeastern Florida). Employing a large-domain approach (i.e., the Western North Atlantic Tidal model domain), two-dimensional tidal flows within the Loxahatchee River estuary are reproduced to provide: 1)...
Show moreRecent cooperative efforts between the University of Central Florida, the Florida Department of Environmental Protection, and the South Florida Water Management District explore the development of a two-dimensional, depth-integrated tidal model for the Loxahatchee River estuary (Southeastern Florida). Employing a large-domain approach (i.e., the Western North Atlantic Tidal model domain), two-dimensional tidal flows within the Loxahatchee River estuary are reproduced to provide: 1) recommendations for the domain extent of an integrated, surface/groundwater, three-dimensional model; 2) nearshore, harmonically decomposed, tidal elevation boundary conditions. Tidal simulations are performed using a two-dimensional, depth-integrated, finite element-based code for coastal and ocean circulation, ADCIRC-2DDI. Multiple variations of an unstructured, finite element mesh are applied to encompass the Loxahatchee River estuary and different spatial extents of the Atlantic Intracoastal Waterway (AIW). Phase and amplitude errors between model output and historical data are quantified at five locations within the Loxahatchee River estuary to emphasize the importance of including the AIW in the computational domain. In addition, velocity residuals are computed globally to reveal significantly different net circulation patterns within the Loxahatchee River estuary, as depending on the spatial coverage of the AIW.
Show less - Date Issued
- 2006
- Identifier
- CFE0000925, ucf:46755
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000925
- Title
- AN INVERSE ALGORITHM TO ESTIMATE THERMAL CONTACT RESISTANCE.
- Creator
-
Gill, Jennifer, Kassab, Alain, University of Central Florida
- Abstract / Description
-
Thermal systems often feature composite regions that are mechanically mated. In general, there exists a significant temperature drop across the interface between such regions which may be composed of similar or different materials. The parameter characterizing this temperature drop is the thermal contact resistance, which is defined as the ratio of the temperature drop to the heat flux normal to the interface. The thermal contact resistance is due to roughness effects between mating surfaces...
Show moreThermal systems often feature composite regions that are mechanically mated. In general, there exists a significant temperature drop across the interface between such regions which may be composed of similar or different materials. The parameter characterizing this temperature drop is the thermal contact resistance, which is defined as the ratio of the temperature drop to the heat flux normal to the interface. The thermal contact resistance is due to roughness effects between mating surfaces which cause certain regions of the mating surfaces to loose contact thereby creating gaps. In these gap regions, the principal modes of heat transfer are conduction across the contacting regions of the interface, conduction or natural convection in the fluid filling the gap regions of the interface, and radiation across the gap surfaces. Moreover, the contact resistance is a function of contact pressure as this can significantly alter the topology of the contact region. The thermal contact resistance is a phenomenologically complex function and can significantly alter prediction of thermal models of complex multi-component structures. Accurate estimates of thermal contact resistances are important in engineering calculations and find application in thermal analysis ranging from relatively simple layered and composite materials to more complex biomaterials. There have been many studies devoted to the theoretical predictions of thermal contact resistance and although general theories have been somewhat successful in predicting thermal contact resistances, most reliable results have been obtained experimentally. This is due to the fact that the nature of thermal contact resistance is quite complex and depends on many parameters including types of mating materials, surface characteristics of the interfacial region such as roughness and hardness, and contact pressure distribution. In experiments, temperatures are measured at a certain number of locations, usually close to the contact surface, and these measurements are used as inputs to a parameter estimation procedure to arrive at the sought-after thermal contact resistance. Most studies seek a single value for the contact resistance, while the resistance may in fact also vary spatially. In this thesis, an inverse problem (IP) is formulated to estimate the spatial variation of the thermal contact resistance along an interface in a two-dimensional configuration. Temperatures measured at discrete locations using embedded sensors appropriately placed in proximity to the interface provide the additional information required to solve the inverse problem. A superposition method serves to determine sensitivity coefficients and provides guidance in the location of the measuring points. Temperature measurements are then used to define a regularized quadratic functional that is minimized to yield the contact resistance between the two mating surfaces. A boundary element method analysis (BEM) provides the temperature field under current estimates of the contact resistance in the solution of the inverse problem when the geometry of interest is not regular, while an analytical solution can be used for regular geometries. Minimization of the IP functional is carried out by the Levenberg-Marquadt method or by a Genetic Algorithm depending on the problem under consideration. The L-curve method of Hansen is used to choose the optimal regularization parameter. A series of numerical examples are provided to demonstrate and validate the approach.
Show less - Date Issued
- 2005
- Identifier
- CFE0000748, ucf:46582
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000748
- Title
- SPORTS MASSAGE RESEARCH PROTOCOLS AND INDUSTRY STANDARDS.
- Creator
-
Kest, Amber, Valdes, Anna, University of Central Florida
- Abstract / Description
-
The purpose of this study was to determine which MT techniques current licensed massage therapists practicing sports massage are using to treat delayed onset muscle soreness (DOMS) by conducting an anonymous online survey of practicing sports massage therapists. The secondary purpose was to determine if previous sports massage research protocols match current practices in sports massage to treat DOMS. There were 85 anonymous respondents ranging in age from 24 to 74 years with a mean age of 44...
Show moreThe purpose of this study was to determine which MT techniques current licensed massage therapists practicing sports massage are using to treat delayed onset muscle soreness (DOMS) by conducting an anonymous online survey of practicing sports massage therapists. The secondary purpose was to determine if previous sports massage research protocols match current practices in sports massage to treat DOMS. There were 85 anonymous respondents ranging in age from 24 to 74 years with a mean age of 44.5 years. Participants included 55 female (65.5%) and 29 male (34.5%) therapists. Professional experience ranged from 4 years or less to more than 20 years, and the majority reported having training specific to sports massage. Previous research methods have placed an overwhelming emphasis on effleurage and petrissage in the treatment protocols to test the effects of massage on DOMS. However, practicing therapists rely on many more techniques and modalities when giving sports massage treatments for DOMS. On a scale of 1 to 5 respondents rated the importance of effleurage strokes in their sports massage treatment at 3.3, petrissage strokes averaged 3.4, friction 3.3, and tapotement ranked slightly lower with a weighted average of 2.1. Sixty six percent of respondents reported that they use stretching techniques often or always. Myofascial release techniques are used sometimes or often for 65% of the respondents, but fewer utilize manual lymphatic drainage in their sports massage. Additional techniques besides those mentioned in the survey are used by 64% of the respondents.
Show less - Date Issued
- 2015
- Identifier
- CFH0004846, ucf:45476
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004846
- Title
- FEAR OF FALLING ASSESSMENT AND INTERVENTIONS IN COMMUNITY-DWELLING OLDER ADULTS: A MIXED METHODS CASE STUDY.
- Creator
-
Cappleman, Amanda S., Thiamwong, Ladda, University of Central Florida
- Abstract / Description
-
Background: Fear of falling has significant adverse physical and psychological effects for the community-dwelling older adult. Objective: The purpose of this study was to assess fear of falling in community-dwelling older adults and explore participant perceptions of fear of falling assessments and interventions. Methods: A mixed methods case study was utilized to gain an in-depth understanding of older adults' perceptions. It consisted of quantitative data collection by objective measures...
Show moreBackground: Fear of falling has significant adverse physical and psychological effects for the community-dwelling older adult. Objective: The purpose of this study was to assess fear of falling in community-dwelling older adults and explore participant perceptions of fear of falling assessments and interventions. Methods: A mixed methods case study was utilized to gain an in-depth understanding of older adults' perceptions. It consisted of quantitative data collection by objective measures and qualitative data collection by four individual in-depth interviews. A sample of four community-dwelling adults aged 65 years and older and living in Orlando, Florida, completed the study in their home environment. To combine quantitative and qualitative data for each participant, a case-specific analysis was used, resulting in narratives with a storytelling approach aiming to explore each participant independently. This was followed by a cross-case analysis to gain a more comprehensive understanding of the participants in relation to one another. Results: Four themes emerged: 1) Feedback from an objective measure is valuable; 2) Family experiences with fear of falling drive personal interventions; 3) Fundamental assessments for fear of falling are missing, and 4) Fluctuating definitions of "fear" contribute to difficulty in assessments and interventions. Conclusion: Clear perceptual themes developed to provide a comprehensive understanding of community-dwelling older adults' perceptions of fear of falling assessments and interventions. Future research is needed to determine how to best combine feedback-oriented assessments with established interventions, such as exercise. Standardization of a subjective measure for fear of falling to use in combination with objective measures is also needed. Keywords: assessment, intervention, fear of falling, older adults, community-dwelling, mixed methods
Show less - Date Issued
- 2019
- Identifier
- CFH2000567, ucf:45683
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000567
- Title
- MESHLESS HEMODYNAMICS MODELING AND EVOLUTIONARY SHAPE OPTIMIZATION OF BYPASS GRAFTS ANASTOMOSES.
- Creator
-
El Zahab, Zaher, Kassab, Alain, University of Central Florida
- Abstract / Description
-
Objectives: The main objective of the current dissertation is to establish a formal shape optimization procedure for a given bypass grafts end-to-side distal anastomosis (ETSDA). The motivation behind this dissertation is that most of the previous ETSDA shape optimization research activities cited in the literature relied on direct optimization approaches that do not guaranty accurate optimization results. Three different ETSDA models are considered herein: The conventional, the Miller cuff,...
Show moreObjectives: The main objective of the current dissertation is to establish a formal shape optimization procedure for a given bypass grafts end-to-side distal anastomosis (ETSDA). The motivation behind this dissertation is that most of the previous ETSDA shape optimization research activities cited in the literature relied on direct optimization approaches that do not guaranty accurate optimization results. Three different ETSDA models are considered herein: The conventional, the Miller cuff, and the hood models. Materials and Methods: The ETSDA shape optimization is driven by three computational objects: a localized collocation meshless method (LCMM) solver, an automated geometry pre-processor, and a genetic-algorithm-based optimizer. The usage of the LCMM solver is very convenient to set an autonomous optimization mechanism for the ETSDA models. The task of the automated pre-processor is to randomly distribute solution points in the ETSDA geometries. The task of the optimized is the adjust the ETSDA geometries based on mitigation of the abnormal hemodynamics parameters. Results: The results reported in this dissertation entail the stabilization and validation of the LCMM solver in addition to the shape optimization of the considered ETSDA models. The LCMM stabilization results consists validating a custom-designed upwinding scheme on different one-dimensional and two-dimensional test cases. The LCMM validation is done for incompressible steady and unsteady flow applications in the ETSDA models. The ETSDA shape optimization include single-objective optimization results in steady flow situations and bi-objective optimization results in pulsatile flow situations. Conclusions: The LCMM solver provides verifiably accurate resolution of hemodynamics and is demonstrated to be third order accurate in a comparison to a benchmark analytical solution of the Navier-Stokes. The genetic-algorithm-based shape optimization approach proved to be very effective for the conventional and Miller cuff ETSDA models. The shape optimization results for those two models definitely suggest that the graft caliber should be maximized whereas the anastomotic angle and the cuff height (in the Miller cuff model) should be chosen following a compromise between the wall shear stress spatial and temporal gradients. The shape optimization of the hood ETSDA model did not prove to be advantageous, however it could be meaningful with the inclusion of the suture line cut length as an optimization parameter.
Show less - Date Issued
- 2008
- Identifier
- CFE0002165, ucf:47927
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002165
- Title
- Investigating and Facilitating the Transferability of Safety Performance Functions.
- Creator
-
Farid, Ahmed Tarek Ahmed, Abdel-Aty, Mohamed, Lee, JaeYoung, Eluru, Naveen, University of Central Florida
- Abstract / Description
-
Safety performance functions (SPFs) are essential analytical tools in the road safety field. The SPFs are statistical regression models used to predict crash counts by roadway facility type, crash type and severity. The national Highway Safety Manual (HSM) is a generic guidebook used for road safety evaluation and enhancement. In it, default SPFs, developed using negative binomial (NB) regression, are provided for multiple facility types and crash categories. Roadway agencies, whether public...
Show moreSafety performance functions (SPFs) are essential analytical tools in the road safety field. The SPFs are statistical regression models used to predict crash counts by roadway facility type, crash type and severity. The national Highway Safety Manual (HSM) is a generic guidebook used for road safety evaluation and enhancement. In it, default SPFs, developed using negative binomial (NB) regression, are provided for multiple facility types and crash categories. Roadway agencies, whether public or private, may opt to not invest their resources in data collection and processing to develop own localized SPFs. Instead, the agencies may adopt the HSM's. However, the HSM's SPFs may not necessarily be applicable to any conditions. Hence, this research is focused on SPF transferability, specifically for rural divided multilane highway segments. Use of Bayesian informative priors to aid in the transferability of NB SPFs, developed for Florida, to California's conditions and vice versa is investigated. It is demonstrated that informative priors facilitate SPF transferability. Furthermore, NB SPFs are developed for Florida, Ohio, Illinois, Minnesota, California, Washington and North Carolina. That is to evaluate the transferability of each state's SPFs to the other states' conditions. The results indicate that Ohio, Illinois, Minnesota and California have SPFs that are transferable to conditions of each of the four states. Also, two methods are proposed for calibrating transferred SPFs to the destinations' conditions and are shown to outperform the SPF calibration methods in the road safety literature. Finally, a variety of modeling frameworks are proposed for developing and transferring SPFs of the seven aforementioned states to each state's data. Not a single model exhibits the best fit when transferred in all cases. However, the Tobit model, NB model and a hybrid model that coalesces the results of both perform the best in a substantial number of the transferred SPFs.
Show less - Date Issued
- 2018
- Identifier
- CFE0007000, ucf:52054
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007000
- Title
- A Contextual Approach to Real Time, Interactive Narrative Generation.
- Creator
-
Hollister, James, Richie, Samuel, Weeks, Arthur, Wanielista, Martin, University of Central Florida
- Abstract / Description
-
Oral story telling has become a lost art of family histories because social media and technology have taken over the personal interactions that once passed on the important stories and facts from generation to generation. This dissertation presents and evaluates a method of generating a narrative with input from the listener without actually forcing him or her to become an actual character in the narrative. This system is called CAMPFIRE Story Telling System (STS) and employs a contextual...
Show moreOral story telling has become a lost art of family histories because social media and technology have taken over the personal interactions that once passed on the important stories and facts from generation to generation. This dissertation presents and evaluates a method of generating a narrative with input from the listener without actually forcing him or her to become an actual character in the narrative. This system is called CAMPFIRE Story Telling System (STS) and employs a contextual approach to story generation. This system uses the Cooperating Context Method (CCM) to generate and tell dynamic stories in real time and can be modified by the listener. CCM was created to overcome the weaknesses found in other contextual approaches during story generation while still meeting the design criteria of 1) being able to plan out a story; 2) being able to create a narrative that is entertaining to the listener; and 3) being able to modify the story that could incorporate the listener's request in the story. The CCM process begins by creating a list of tasks by analyzing the current situation. A list of contexts is narrowed down through a series of algorithms into two lists: high priority and low priority lists. These lists are analyzed and a set of context best suited to handle the tasks are selected. The CAMPFIRE STS was rigorously assessed for its functionality, novelty, and user acceptance as well as the time needed to modify the knowledge base. These evaluations showed that the CAMPFIRE STS has the ability to create novel stories using the same knowledge base. A group of 38 test subjects used and evaluated CAMPFIRE STS with respect to its use for children, story entertainment, story creativity and the system's ease of use answering a extensive survey of 54 questions. The survey showed that CAMPFIRE STS can create stories appropriate for bedtime stories with some minor modifications and that the generated stories are novel and entertaining stories, and that it was an easy system to use.
Show less - Date Issued
- 2016
- Identifier
- CFE0006687, ucf:51923
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006687
- Title
- HIGH QUALITY GATE DIELECTRIC/MoS2 INTERFACES PROBED BY THE CONDUCTANCE METHOD.
- Creator
-
Krishnaprasad Sharada, Adithi Pandrahal, Roy, Tania, Abdolvand, Reza, Yuan, Jiann-Shiun, University of Central Florida
- Abstract / Description
-
Two-dimensional materials provide a versatile platform for various electronic and optoelectronic devices, due to their uniform thickness and pristine surfaces. We probe the superior quality of 2D/2D and 2D/3D interfaces by fabricating molybdenum disulfide (MoS2)-based field effect transistors having hexagonal boron nitride (h-BN) and Al2O3 as the top gate dielectrics. An extremely low trap density of ~7x10^10 states/cm2-eV is extracted at the 2D/2D interfaces with h-BN as the top gate...
Show moreTwo-dimensional materials provide a versatile platform for various electronic and optoelectronic devices, due to their uniform thickness and pristine surfaces. We probe the superior quality of 2D/2D and 2D/3D interfaces by fabricating molybdenum disulfide (MoS2)-based field effect transistors having hexagonal boron nitride (h-BN) and Al2O3 as the top gate dielectrics. An extremely low trap density of ~7x10^10 states/cm2-eV is extracted at the 2D/2D interfaces with h-BN as the top gate dielectric on the MoS2 channel. 2D/3D interfaces with Al2O3 as the top gate dielectric and SiOx as the nucleation layer exhibit trap densities between 7x10^10 and 10^11 states/cm2-eV, which is lower than previously reported 2D-channel/high-k-dielectric interface trap densities. The comparable values of trap time constants for both interfaces imply that similar types of defects contribute to the interface traps. This work establishes the case for van der Waals systems where the superior quality of 2D/2D and 2D/high-k dielectric interfaces can produce high performance electronic and optoelectronic devices.
Show less - Date Issued
- 2018
- Identifier
- CFE0007214, ucf:52209
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007214
- Title
- A Localized Blended RBF Collocation Method for Effective Shock Capturing.
- Creator
-
Harris, Michael, Kassab, Alain, Moslehy, Faissal, Divo, Eduardo, Chopra, Manoj, University of Central Florida
- Abstract / Description
-
Solving partial differential equations (PDEs) can require numerical methods, especially for non-linear problems and complex geometry. Common numerical methods used today are the finite difference method (FDM), finite element method (FEM) and the finite volume method (FVM). These methods require a mesh or grid before a solution is attempted. Developing the mesh can require expensive preprocessing time and the quality of the mesh can have major effects on the solution. In recent years, meshless...
Show moreSolving partial differential equations (PDEs) can require numerical methods, especially for non-linear problems and complex geometry. Common numerical methods used today are the finite difference method (FDM), finite element method (FEM) and the finite volume method (FVM). These methods require a mesh or grid before a solution is attempted. Developing the mesh can require expensive preprocessing time and the quality of the mesh can have major effects on the solution. In recent years, meshless methods have become a research interest due to the simplicity of using scattered data points. Many types of meshless methods exist stemming from the spectral or pseudo-spectral methods, but the focus of this research involves a meshless method using radial basis function (RBF) interpolation. Radial basis functions (RBF) interpolation is a class of meshless method and can be used in solving partial differential equations. Radial basis functions are impressive because of the capability of multivariate interpolation over scattered data, even for data with discontinuities. Also, radial basis function interpolation is capable of spectral accuracy and exponential convergence. For infinitely smooth radial basis functions such as the Hardy Multiquadric and inverse Multiquadric, the RBF is dependent on a shape parameter that must be chosen properly to obtain accurate approximations. The optimum shape parameter can vary depending on the smoothness of the field. Typically, the shape parameter is chosen to be a large value rendering the RBF flat and yielding high condition number interpolation matrix. This strategy works well for smooth data and as shown to produce phenomenal results for problems in heat transfer and incompressible fluid dynamics. The approach of flat RBF or high condition matrices tends to fail for steep gradients and shocks. Instead, a low-value shape parameter rendering the RBF steep and the condition number of the interpolation matrix small should be used in the presence of steep gradients or shocks. This work demonstrates a method to capture steep gradients and shocks using a blended RBF approach. The method switches between flat and steep RBF interpolation depending on the smoothness of the data. Flat RBF or high condition number RBF interpolation is used for smooth regions maintaining high accuracy. Steep RBF or low condition number RBF interpolation provides stability for steep gradients and shocks. This method is demonstrated using several numerical experiments such as 1-D advection equation, 2-D advection equation, Burgers equation, 2-D inviscid compressible Euler equations, and the Navier-Stokes equations.
Show less - Date Issued
- 2018
- Identifier
- CFE0007332, ucf:52108
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007332
- Title
- INVERSE BOUNDARY ELEMENT/GENETIC ALGORITHM METHOD FOR RECONSTRUCTION OF MULTI-DIMENSIONAL HEAT FLUX DISTRIBUTIONS WITH FILM COOLING APPLICATIONS.
- Creator
-
Silieti, Mahmood, Kassab, Alain, University of Central Florida
- Abstract / Description
-
A methodology is formulated for the solution of the inverse problem concerned with the reconstruction of multi-dimensional heat fluxes for film cooling applications. The motivation for this study is the characterization of complex thermal conditions in industrial applications such as those encountered in film cooled turbomachinery components. The heat conduction problem in the metal endwall/shroud is solved using the boundary element method (bem), and the inverse problem is solved using a...
Show moreA methodology is formulated for the solution of the inverse problem concerned with the reconstruction of multi-dimensional heat fluxes for film cooling applications. The motivation for this study is the characterization of complex thermal conditions in industrial applications such as those encountered in film cooled turbomachinery components. The heat conduction problem in the metal endwall/shroud is solved using the boundary element method (bem), and the inverse problem is solved using a genetic algorithm (ga). Thermal conditions are overspecified at exposed surfaces amenable to measurement, while the temperature and surface heat flux distributions are unknown at the film cooling hole/slot walls. The latter are determined in an iterative process by developing two approaches. The first approach, developed for 2d applications, solves an inverse problem whose objective is to adjust the film cooling hole/slot wall temperatures and heat fluxes until the temperature and heat flux at the measurement surfaces are matched in an overall heat conduction solution. The second approach, developed for 2d and 3d applications, is to distribute a set of singularities (sinks) at the vicinity of the cooling slots/holes surface inside a fictitious extension of the physical domain or along cooling hole centerline with a given initial strength distribution. The inverse problem iteratively alters the strength distribution of the singularities (sinks) until the measuring surfaces heat fluxes are matched. The heat flux distributions are determined in a post-processing stage after the inverse problem is solved. The second approach provides a tremendous advantage in solving the inverse problem, particularly in 3d applications, and it is recommended as the method of choice for this class of problems. It can be noted that the ga reconstructed heat flux distributions are robust, yielding accurate results to both exact and error-laden inputs. In all cases in this study, results from experiments are simulated using a full conjugate heat transfer (cht) finite volume models which incorporate the interactions of the external convection in the hot turbulent gas, internal convection within the cooling plena, and the heat conduction in the metal endwall/shroud region. Extensive numerical investigations are undertaken to demonstrate the significant importance of conjugate heat transfer in film cooling applications and to identify the implications of various turbulence models in the prediction of accurate and more realistic surface temperatures and heat fluxes in the cht simulations. These, in turn, are used to provide numerical inputs to the inverse problem. Single and multiple cooling slots, cylindrical cooling holes, and fan-shaped cooling holes are considered in this study. The turbulence closure is modeled using several two-equation approach, the four-equation turbulence model, as well as five and seven moment reynolds stress models. The predicted results, by the different turbulence models, for the cases of adiabatic and conjugate models, are compared to experimental data reported in the open literature. Results show the significant effects of conjugate heat transfer on the temperature field in the film cooling hole region, and the additional heating up of the cooling jet itself. Moreover, results from the detailed numerical studies presented in this study validate the inverse problem approaches and reveal good agreement between the bem/ga reconstructed heat fluxes and the cht simulated heat fluxes along the inaccessible cooling slot/hole walls
Show less - Date Issued
- 2004
- Identifier
- CFE0000166, ucf:52896
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000166
- Title
- Multiphase Flow Modeling of Molten Metal Atomization at High Gas Pressure.
- Creator
-
Hanthanan Arachchilage, Kalpana, Kumar, Ranganathan, Sohn, Yongho, Kassab, Alain, Shivamoggi, Bhimsen, University of Central Florida
- Abstract / Description
-
The high-pressure gas atomization is well known as one of the best powder manufacturing processes due to its controllability over powder size distribution. However, with the continuous improvement of new alloys, optimizing the operating parameters to maximize the yield is costly and time-consuming. Therefore, it is essential to understand the high-pressure gas atomization process and the effects of different operational parameters on the powder size distribution.Two-phase numerical...
Show moreThe high-pressure gas atomization is well known as one of the best powder manufacturing processes due to its controllability over powder size distribution. However, with the continuous improvement of new alloys, optimizing the operating parameters to maximize the yield is costly and time-consuming. Therefore, it is essential to understand the high-pressure gas atomization process and the effects of different operational parameters on the powder size distribution.Two-phase numerical simulations are performed to capture the interfacial dynamic during the atomization process and to obtain the effects of gas pressure, melt flow rate, and thermophysical properties of atomizing gas and the molten metal. The Volume of Fluid (VOF) model is used to capture the melt-gas interface, and in-house post-processing code is developed to obtain the droplet size distributions. Three-dimensional geometry of an annular-slit close-coupled gas atomizer is utilized to investigate the primary atomization process. The current grid resolution is sufficient forcapturing primary atomization and some characteristics of the secondary atomization, but it is not adequate to capture all the length scales in secondary atomization. Qualitative comparisons of the cumulative volume graphs indicate that this numerical approach is capable of capturing the trends in the atomization process as in the experiments. It is found that a combination of several interfacial instabilities governs the atomization process. Simulations corresponding to different gas pressures show that the atomizationcharacteristics remain unchanged irrespective of the gas pressure. However, it is found that the rate of the evolution and the effectiveness of the atomization process increases with the gas pressure. Three melts (aluminum, steel, and an artificial material with intermediate thermophysical properties) are used to investigate the effects of the molten metal properties and found that the rate of the atomization process decreases with increasing melt density, and the yield of the atomized powder is seen to increase. The flow characteristics remain unchanged for all three melts. The melt flow is strongly correlated with flow characteristics and interfacial instability.
Show less - Date Issued
- 2019
- Identifier
- CFE0007814, ucf:52342
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007814
- Title
- Learning Kernel-based Approximate Isometries.
- Creator
-
Sedghi, Mahlagha, Georgiopoulos, Michael, Anagnostopoulos, Georgios, Atia, George, Liu, Fei, University of Central Florida
- Abstract / Description
-
The increasing availability of public datasets offers an inexperienced opportunity to conduct data-driven studies. Metric Multi-Dimensional Scaling aims to find a low-dimensional embedding of the data, preserving the pairwise dissimilarities amongst the data points in the original space. Along with the visualizability, this dimensionality reduction plays a pivotal role in analyzing and disclosing the hidden structures in the data. This work introduces Sparse Kernel-based Least Squares Multi...
Show moreThe increasing availability of public datasets offers an inexperienced opportunity to conduct data-driven studies. Metric Multi-Dimensional Scaling aims to find a low-dimensional embedding of the data, preserving the pairwise dissimilarities amongst the data points in the original space. Along with the visualizability, this dimensionality reduction plays a pivotal role in analyzing and disclosing the hidden structures in the data. This work introduces Sparse Kernel-based Least Squares Multi-Dimensional Scaling approach for exploratory data analysis and, when desirable, data visualization. We assume our embedding map belongs to a Reproducing Kernel Hilbert Space of vector-valued functions which allows for embeddings of previously unseen data. Also, given appropriate positive-definite kernel functions, it extends the applicability of our methodto non-numerical data. Furthermore, the framework employs Multiple Kernel Learning for implicitlyidentifying an effective feature map and, hence, kernel function. Finally, via the use ofsparsity-promoting regularizers, the technique is capable of embedding data on a, typically, lowerdimensionalmanifold by naturally inferring the embedding dimension from the data itself. In theprocess, key training samples are identified, whose participation in the embedding map's kernelexpansion is most influential. As we will show, such influence may be given interesting interpretations in the context of the data at hand. The resulting multi-kernel learning, non-convex framework can be effectively trained via a block coordinate descent approach, which alternates between an accelerated proximal average method-based iterative majorization for learning the kernel expansion coefficients and a simple quadratic program, which deduces the multiple-kernel learning coefficients. Experimental results showcase potential uses of the proposed framework on artificial data as well as real-world datasets, that underline the merits of our embedding framework. Our method discovers genuine hidden structure in the data, that in case of network data, matches the results of well-known Multi- level Modularity Optimization community structure detection algorithm.
Show less - Date Issued
- 2017
- Identifier
- CFE0007132, ucf:52315
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007132
- Title
- Analytical and Numerical Investigations of the Kudryashov Generalized KdV Equation.
- Creator
-
Hilton, William, Schober, Constance, Moore, Brian, Choudhury, Sudipto, University of Central Florida
- Abstract / Description
-
This thesis concerns an analytical and numerical study of the Kudryashov Generalized Korteweg-de Vries (KG KdV) equation. Using a refined perturbation expansion of the Fermi-Pasta-Ulam (FPU) equations of motion, the KG KdV equation, which arises at sixth order, and general higher order KdV equations are derived. Special solutions of the KG KdV equation are derived using the tanh method. A pseudospectral integrator, which can handle stiff equations, is developed for the higher order KdV...
Show moreThis thesis concerns an analytical and numerical study of the Kudryashov Generalized Korteweg-de Vries (KG KdV) equation. Using a refined perturbation expansion of the Fermi-Pasta-Ulam (FPU) equations of motion, the KG KdV equation, which arises at sixth order, and general higher order KdV equations are derived. Special solutions of the KG KdV equation are derived using the tanh method. A pseudospectral integrator, which can handle stiff equations, is developed for the higher order KdV equations. The numerical experiments indicate that although the higher order equations exhibit complex dynamics, they fail to reach energy equipartition on the time scale considered.
Show less - Date Issued
- 2018
- Identifier
- CFE0007754, ucf:52395
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007754
- Title
- Using argument as a bridge between literacy and science: An intervention study in a science methods course for elementary preservice teachers.
- Creator
-
Grysko, Rebeca, Zygouris-Coe, Vassiliki, Gao, Su, Roberts, Sherron, Fang, Zhihui, Bai, Haiyan, University of Central Florida
- Abstract / Description
-
The purpose of this study was to investigate the impact of an intervention on teaching science as argument within a science methods course on elementary preservice teachers' (PSTs') (a) understandings of the nature of science (NOS), (b) knowledge about argumentation, (c) complexity of their written explanations, and (d) ability to incorporate components of the framework for teaching science as argument to support students' literacy and science learning. This mixed-methods study utilized an...
Show moreThe purpose of this study was to investigate the impact of an intervention on teaching science as argument within a science methods course on elementary preservice teachers' (PSTs') (a) understandings of the nature of science (NOS), (b) knowledge about argumentation, (c) complexity of their written explanations, and (d) ability to incorporate components of the framework for teaching science as argument to support students' literacy and science learning. This mixed-methods study utilized an embedded quasi-experimental design with a treatment (n = 20) and control group (n = 25). The treatment group instructor, who completed an eight-week professional development course, implemented the intervention protocol across a 12-week period. Throughout the intervention, emphasis was placed on three key components of teaching science as argument (i.e., argument structure, public reasoning, and the language of science). The control group instructor, who did not partake in any professional learning activities, implemented business-as-usual instruction. Results from a repeated measures MANOVA revealed that, although the intervention did not have a significant impact on PSTs' knowledge of argumentation, PSTs who received the intervention did demonstrate a significant increase in their understanding of the NOS and in the complexity of their written explanations, as compared to PSTs who did not receive the intervention. Furthermore, analysis of PSTs' written lesson plans revealed several themes (i.e., opportunities for students to collect and analyze data, use of scaffolds for helping students construct scientific explanations, emphasis on the use of text to support scientific inquiry, and attention to developing students' science vocabulary) consistent with the framework for teaching science as argument. These findings contribute to a growing body of evidence illustrating the effectiveness of intentionally designed teacher preparation experiences for developing PSTs' knowledge, beliefs, and practices for supporting students' engagement in scientific explanation and argument.
Show less - Date Issued
- 2019
- Identifier
- CFE0007643, ucf:52477
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007643
- Title
- Automated Synthesis of Memristor Crossbar Networks.
- Creator
-
Chakraborty, Dwaipayan, Jha, Sumit Kumar, Leavens, Gary, Ewetz, Rickard, Valliyil Thankachan, Sharma, Xu, Mengyu, University of Central Florida
- Abstract / Description
-
The advancement of semiconductor device technology over the past decades has enabled the design of increasingly complex electrical and computational machines. Electronic design automation (EDA) has played a significant role in the design and implementation of transistor-based machines. However, as transistors move closer toward their physical limits, the speed-up provided by Moore's law will grind to a halt. Once again, we find ourselves on the verge of a paradigm shift in the computational...
Show moreThe advancement of semiconductor device technology over the past decades has enabled the design of increasingly complex electrical and computational machines. Electronic design automation (EDA) has played a significant role in the design and implementation of transistor-based machines. However, as transistors move closer toward their physical limits, the speed-up provided by Moore's law will grind to a halt. Once again, we find ourselves on the verge of a paradigm shift in the computational sciences as newer devices pave the way for novel approaches to computing. One of such devices is the memristor -- a resistor with non-volatile memory.Memristors can be used as junctional switches in crossbar circuits, which comprise of intersecting sets of vertical and horizontal nanowires. The major contribution of this dissertation lies in automating the design of such crossbar circuits -- doing a new kind of EDA for a new kind of computational machinery. In general, this dissertation attempts to answer the following questions:a. How can we synthesize crossbars for computing large Boolean formulas, up to 128-bit?b. How can we synthesize more compact crossbars for small Boolean formulas, up to 8-bit?c. For a given loop-free C program doing integer arithmetic, is it possible to synthesize an equivalent crossbar circuit?We have presented novel solutions to each of the above problems. Our new, proposed solutions resolve a number of significant bottlenecks in existing research, via the usage of innovative logic representation and artificial intelligence techniques. For large Boolean formulas (up to 128-bit), we have utilized Reduced Ordered Binary Decision Diagrams (ROBDDs) to automatically synthesize linearly growing crossbar circuits that compute them. This cutting edge approach towards flow-based computing has yielded state-of-the-art results. It is worth noting that this approach is scalable to n-bit Boolean formulas. We have made significant original contributions by leveraging artificial intelligence for automatic synthesis of compact crossbar circuits. This inventive method has been expanded to encompass crossbar networks with 1D1M (1-diode-1-memristor) switches, as well. The resultant circuits satisfy the tight constraints of the Feynman Grand Prize challenge and are able to perform 8-bit binary addition. A leading edge development for end-to-end computation with flow-based crossbars has been implemented, which involves methodical translation of loop-free C programs into crossbar circuits via automated synthesis. The original contributions described in this dissertation reflect the substantial progress we have made in the area of electronic design automation for synthesis of memristor crossbar networks.
Show less - Date Issued
- 2019
- Identifier
- CFE0007609, ucf:52528
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007609
- Title
- MONITORING SHALLOW CONTROLLED GRAVES CONTAINING SMALL CADAVERS USING GROUND PENETRATING RADAR.
- Creator
-
Fletcher, Joanna, Schultz, John, University of Central Florida
- Abstract / Description
-
Ground-penetrating radar (GPR) can be a useful geophysical instrument in the search and detection of clandestine graves in a forensic context. Controlled research in the field of forensic archaeology has demonstrated the applicability of this technology and is vital for improving GPR search methods. The objectives of this research was to evaluate the applicability of GPR, using 250 MHz and 500 MHz antennae, to locate shallow graves containing small pig cadavers in various burial scenarios...
Show moreGround-penetrating radar (GPR) can be a useful geophysical instrument in the search and detection of clandestine graves in a forensic context. Controlled research in the field of forensic archaeology has demonstrated the applicability of this technology and is vital for improving GPR search methods. The objectives of this research was to evaluate the applicability of GPR, using 250 MHz and 500 MHz antennae, to locate shallow graves containing small pig cadavers in various burial scenarios over a 12 month period. Data was collected on a controlled grid containing six graves at 0.5 m in depth: five graves containing pig carcasses and one control grave. The five graves containing the pig carcasses were devised to test a number of common forensic burial scenarios. The reflection profile data was processed using the computer program REFLEXW. The results demonstrate that the additional grave items did not always increase the detection of the grave for this monitoring period. Further, the low demarcation of the grave containing disturbed backfill illustrated that the hyperbolic reflection features were the result of the pig carcasses and not the disturbed soil. In terms of antenna performance, the 250 MHz data initially provided a higher resolution within the first few months. However, over time the higher detail provided by the 500 MHz data consistently resulted in easily discernable reflections.
Show less - Date Issued
- 2011
- Identifier
- CFE0003592, ucf:48883
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003592
- Title
- DETERMINING THE PRESENCE OF AN IGNITABLE LIQUID RESIDUE IN FIRE DEBRIS SAMPLES UTILIZING TARGET FACTOR ANALYSIS.
- Creator
-
McHugh, Kelly, Sigman, Michael, University of Central Florida
- Abstract / Description
-
Current fire debris analysis procedure involves using the chromatographic patterns of total ion chromatograms, extracted ion chromatograms, and target compound analysis to identify an ignitable liquid according to the American Society for Testing and Materials (ASTM) E 1618 standard method. Classifying the ignitable liquid is accomplished by a visual comparison of chromatographic data obtained from any extracted ignitable liquid residue in the debris to the chromatograms of ignitable liquids...
Show moreCurrent fire debris analysis procedure involves using the chromatographic patterns of total ion chromatograms, extracted ion chromatograms, and target compound analysis to identify an ignitable liquid according to the American Society for Testing and Materials (ASTM) E 1618 standard method. Classifying the ignitable liquid is accomplished by a visual comparison of chromatographic data obtained from any extracted ignitable liquid residue in the debris to the chromatograms of ignitable liquids in a database, i.e. by visual pattern recognition. Pattern recognition proves time consuming and introduces potential for human error. One particularly difficult aspect of fire debris analysis is recognizing an ignitable liquid residue when the intensity of its chromatographic pattern is extremely low or masked by pyrolysis products. In this research, a unique approach to fire debris analysis was applied by utilizing the samplesÂÂ' total ion spectrum (TIS) to identify an ignitable liquid, if present. The TIS, created by summing the intensity of each ion across all elution times in a gas chromatography-mass spectrometry (GC-MS) dataset retains sufficient information content for the identification of complex mixtures . Computer assisted spectral comparison was then performed on the samplesÂÂ' TIS by target factor analysis (TFA). This approach allowed rapid automated searching against a library of ignitable liquid summed ion spectra. Receiver operating characteristic (ROC) curves measured how well TFA identified ignitable liquids in the database that were of the same ASTM classification as the ignitable liquid in fire debris samples, as depicted in their corresponding area under the ROC curve. This study incorporated statistical analysis to aid in classification of an ignitable liquid, therefore alleviating interpretive error inherent in visual pattern recognition. This method could allow an analyst to declare an ignitable liquid present when utilization of visual pattern recognition alone is not sufficient.
Show less - Date Issued
- 2010
- Identifier
- CFE0003042, ucf:48337
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003042
- Title
- NUMERICAL COMPUTATIONS FOR PDE MODELS OF ROCKET EXHAUST FLOW IN SOIL.
- Creator
-
Brennan, Brian, Moore, Brian, University of Central Florida
- Abstract / Description
-
We study numerical methods for solving the nonlinear porous medium and Navier-Lame problems. When coupled together, these equations model the flow of exhaust through a porous medium, soil, and the effects that the pressure has on the soil in terms of spatial displacement. For the porous medium equation we use the Crank-Nicolson time stepping method with a spectral discretization in space. Since the Navier-Lame equation is a boundary value problem, it is solved using a finite element method...
Show moreWe study numerical methods for solving the nonlinear porous medium and Navier-Lame problems. When coupled together, these equations model the flow of exhaust through a porous medium, soil, and the effects that the pressure has on the soil in terms of spatial displacement. For the porous medium equation we use the Crank-Nicolson time stepping method with a spectral discretization in space. Since the Navier-Lame equation is a boundary value problem, it is solved using a finite element method where the spatial domain is represented by a triangulation of discrete points. The two problems are coupled by using approximations of solutions to the porous medium equation to define the forcing term in the Navier-Lame equation. The spatial displacement solutions can be used to approximate the strain and stress imposed on the soil. An analysis of these physical properties shows whether or not the material ceases to act as an elastic material and instead behaves like a plastic which will tell us if the soil has failed and a crater has formed. Analytical as well as experimental tests are used to find a good balance for solving the porous medium and Navier-Lame equations both accurately and efficiently.
Show less - Date Issued
- 2010
- Identifier
- CFE0003217, ucf:48565
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003217
