Current Search: Structural (x)
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- Title
- GRATING COUPLER FOR SURFACE WAVES BASED ON ELECTRICAL DISPLACEMENT CURRENTS.
- Creator
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Brescia, Jonathan R, Peale, Robert, University of Central Florida
- Abstract / Description
-
Bound electromagnetic surface waves can be excited by free-space waves on a corrugated conduction surface. These electromagnetic surface waves, called surface plasmon polaritons (SPPs), are coupled to a plasma of free charges, which travel together with the wave. We investigated the effect of separating metal corrugations from the smooth metal ground plane with a thin dielectric layer and show that SPPs can be excited via displacement currents. However, the SPP excitation resonances broaden...
Show moreBound electromagnetic surface waves can be excited by free-space waves on a corrugated conduction surface. These electromagnetic surface waves, called surface plasmon polaritons (SPPs), are coupled to a plasma of free charges, which travel together with the wave. We investigated the effect of separating metal corrugations from the smooth metal ground plane with a thin dielectric layer and show that SPPs can be excited via displacement currents. However, the SPP excitation resonances broaden and disappear as the dielectric thickness approaches 1% of the wavelength.
Show less - Date Issued
- 2019
- Identifier
- CFH2000457, ucf:45898
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000457
- Title
- Evaluation of an Early Classic Round Structure at Santa Rita Corozal, Belize.
- Creator
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Kangas, Rachael, Chase, Arlen, Chase, Diane, Barber, Sarah, University of Central Florida
- Abstract / Description
-
Round structures in the Maya area are an architectural form that is not well understood, in part due to the relatively few examples recovered through archaeological excavations. The site of Santa Rita Corozal, Belize offers one of the few examples of an Early Classic Period round structure (Structure 135) in the Maya region, one that is distinctive in its timing and architectural form. This thesis seeks to compare Structure 135 with the patterns of round structures identified in the...
Show moreRound structures in the Maya area are an architectural form that is not well understood, in part due to the relatively few examples recovered through archaeological excavations. The site of Santa Rita Corozal, Belize offers one of the few examples of an Early Classic Period round structure (Structure 135) in the Maya region, one that is distinctive in its timing and architectural form. This thesis seeks to compare Structure 135 with the patterns of round structures identified in the Preclassic and Terminal/early Postclassic Periods, when there are comparatively more examples and to pinpoint the multiple construction periods evidenced in the excavations to define the changes to the structure over time. Based on this research, Structure 135 at Santa Rita Corozal does not clearly conform to earlier or later patterns of round structures in the Maya region and its use before abandonment and eventual transformation to a rectilinear shape was shorter than previously thought. This research also offers insights into the need for the contextual analysis of ceramics, and the difficulties of assuming context through the use of construction fill, even with a clear cultural formation process.
Show less - Date Issued
- 2015
- Identifier
- CFE0005962, ucf:50798
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005962
- Title
- Investigation of Multiscale Fluid Structure Interaction Modeling of Flow in Arterial Systems.
- Creator
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Sotelo, Sebastian, Kassab, Alain, Ilie, Marcel, Divo, Eduardo, University of Central Florida
- Abstract / Description
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The study of hemodynamic patterns in large blood vessels, such as the ascending aortic artery, brachiocephalic trunk, right carotid artery and right subclavian artery presents the challenging complexity of vessel wall compliance induced by the high levels of shear stress gradients and blood flow pulsatility. Accurate prediction of hemodynamics in such conditions requires a complete Fluid Structure Interaction (FSI) analysis that couples the fluid flow behavior throughout the cardiac cycle...
Show moreThe study of hemodynamic patterns in large blood vessels, such as the ascending aortic artery, brachiocephalic trunk, right carotid artery and right subclavian artery presents the challenging complexity of vessel wall compliance induced by the high levels of shear stress gradients and blood flow pulsatility. Accurate prediction of hemodynamics in such conditions requires a complete Fluid Structure Interaction (FSI) analysis that couples the fluid flow behavior throughout the cardiac cycle with the structural response of the vessel walls. This research focuses on the computational study of a Multiscale Fluid-Structure Interaction on the arterial wall by coupling Finite Volumes Method (FVM) predictions of the Fluid Dynamics within the artery with Finite Elements Method (FEM) predictions of the Elasto-Dynamics response of the arterial walls and 1-D closed loop electrical circuit system to generate the dynamic pressure pulse. To this end, a commercial FVM Computational Fluid Dynamics (CFD) code (STAR-CCM+ 7.09.012) will be coupled through an external interface with a commercial FEM Elasto-Dynamics code (ABAQUS V6.12). The coupling interface is written in such a way that the wall shear stresses and pressures predicted by the CFD analysis will be passed as boundary conditions to the FEM structural solver. The deformations predicted by the FEM structural solver will be passed to the CFD solver to update the geometry in an implicit manner before the following iteration step. The coupling between the FSI and the 1-D closed loop lump parameter circuit updated the pressure pulse and mass flow rates generated by the circuit in an explicit manner after the periodic solution in the FSI analysis had settled. The methodology resulting from this study will be incorporated in a larger collaborative research program between UCF and ORHS that entails optimization of surgical implantation of Left Ventricular Assist Devices (LVAD) cannulae and bypass grafts with the aim to minimize thrombo-embolic events. Moreover, the work proposed will also be applied to another such collaborative project focused on the computational fluid dynamics modeling of the circulation of congenitally affected cardiovascular systems of neonates, specifically the Norwood and Hybrid Norwood circulation of children affected by the hypoplastic left heart syndrome.
Show less - Date Issued
- 2013
- Identifier
- CFE0004753, ucf:49794
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004753
- Title
- HOMOPHOBIA AND HIV TRANSMISSION: A SIX COUNTRY COMPARATIVE ANALYSIS.
- Creator
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Middleton, Tiernan, Mishtal, Joanna, University of Central Florida
- Abstract / Description
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This interdisciplinary study combines epidemiological data with anthropological theory to investigate the relationship between HIV transmission rates and systemic homophobia. Previous research has illustrated the link between high levels of structural violence and structural stigma to increased risk of diseases such as the link between African-Americans and heart disease. This study investigates the relationship between systemic homophobia and HIV transmission rates. Through operationalizing...
Show moreThis interdisciplinary study combines epidemiological data with anthropological theory to investigate the relationship between HIV transmission rates and systemic homophobia. Previous research has illustrated the link between high levels of structural violence and structural stigma to increased risk of diseases such as the link between African-Americans and heart disease. This study investigates the relationship between systemic homophobia and HIV transmission rates. Through operationalizing homophobia into seven distinct factors, I evaluated systemic homophobia in six countries, assigning a score 1-10 to each factor using secondary source aggregation. I compared composite scores, as well as scores in each operationalized factor to HIV transmission rates in those countries. The results of this study indicate a correlation between systemic homophobia and increased HIV transmission, particularly in respect to the factors Marriage Equality, LGBT Laws, Religiosity, LGBT Visibility, and Hate Crimes. Though various sociocultural factors play a role in HIV transmission, this study indicates that homophobia plays an integral role in HIV transmission. This project has pertinent applications in epidemiology, anthropology and public health illustrating the integral role of sociocultural and systemic factors that increase structural violence and risk for a disease.
Show less - Date Issued
- 2015
- Identifier
- CFH0004814, ucf:45458
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004814
- Title
- Computational Methods for Comparative Non-coding RNA Analysis: from Secondary Structures to Tertiary Structures.
- Creator
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Ge, Ping, Zhang, Shaojie, Guha, Ratan, Stanley, Kenneth, Jha, Sumit, Song, Hojun, University of Central Florida
- Abstract / Description
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Unlike message RNAs (mRNAs) whose information is encoded in the primary sequences, the cellular roles of non-coding RNAs (ncRNAs) originate from the structures. Therefore studying the structural conservation in ncRNAs is important to yield an in-depth understanding of their functionalities. In the past years, many computational methods have been proposed to analyze the common structural patterns in ncRNAs using comparative methods. However, the RNA structural comparison is not a trivial task,...
Show moreUnlike message RNAs (mRNAs) whose information is encoded in the primary sequences, the cellular roles of non-coding RNAs (ncRNAs) originate from the structures. Therefore studying the structural conservation in ncRNAs is important to yield an in-depth understanding of their functionalities. In the past years, many computational methods have been proposed to analyze the common structural patterns in ncRNAs using comparative methods. However, the RNA structural comparison is not a trivial task, and the existing approaches still have numerous issues in efficiency and accuracy. In this dissertation, we will introduce a suite ofnovel computational tools that extend the classic models for ncRNA secondary and tertiary structure comparisons.For RNA secondary structure analysis, we first developed a computational tool, named PhyloRNAalifold, to integrate the phylogenetic information into the consensus structural folding. The underlying idea of this algorithm is that the importance of a co-varying mutation should be determined by its position on the phylogenetic tree. By assigning high scores to the critical covariances, the prediction of RNA secondary structure can be more accurate. Besides structure prediction, we also developed a computational tool, named ProbeAlign, to improvethe efficiency of genome-wide ncRNA screening by using high-throughput RNA structural probing data. It treats the chemical reactivities embedded in the probing information as pairing attributes of the searching targets. This approach can avoid the time-consuming base pair matching in the secondary structure alignment. The application of ProbeAlign to the FragSeq datasets shows its capability of genome-wide ncRNAs analysis.For RNA tertiary structure analysis, we first developed a computational tool, named STAR3D, to find the global conservation in RNA 3D structures. STAR3D aims at finding the consensus of stacks by using 2D topology and 3D geometry together. Then, the loop regions can be ordered and aligned according to their relative positions in the consensus. This stack-guided alignment method adopts the divide-and-conquer strategy into RNA 3D structural alignment, which has improved its efficiency dramatically. Furthermore, we also have clustered all loop regions in non-redundant RNA 3D structures to de novo detect plausible RNA structural motifs. The computational pipeline, named RNAMSC, was extended to handle large-scale PDB datasets, and solid downstream analysis was performed to ensure the clustering results are valid and easily to be applied to further research. The final results contain many interesting variations of known motifs, such as GNAA tetraloop, kink-turn, sarcin-ricin and t-loops. We also discovered novel functional motifs that conserved in a wide range of ncRNAs, including ribosomal RNA, sgRNA, SRP RNA, GlmS riboswitch and twister ribozyme.
Show less - Date Issued
- 2016
- Identifier
- CFE0006104, ucf:51212
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006104
- Title
- EFFECTS OF RELAXED ASSUMPTIONS ON THE STATE SWITCHING TECHNIQUE.
- Creator
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Ilardi, Stephen, Kauffman, Jeffrey, University of Central Florida
- Abstract / Description
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This thesis explores the effects of two assumptions commonly used in mathematical models related to a piezoelectric damping method known as State Switching. The technique relies on changing the stiffness state of a piezoelectric patch through control of the electrical boundary conditions. The transition between stiffness states is assumed to occur instantaneously and in concurrence with the switch event. In actuality, the transition will occur over a finite time and will trail behind the...
Show moreThis thesis explores the effects of two assumptions commonly used in mathematical models related to a piezoelectric damping method known as State Switching. The technique relies on changing the stiffness state of a piezoelectric patch through control of the electrical boundary conditions. The transition between stiffness states is assumed to occur instantaneously and in concurrence with the switch event. In actuality, the transition will occur over a finite time and will trail behind the switch event by a finite time. For these assumptions to be valid, the effects of switch duration and delay on the performance of the State Switching method must be examined. In this thesis, the vibration reduction for various switch duration/delay values will be calculated using a numerical solver. The results of the simulations will be used to provide a range in which the two aforementioned assumptions produce negligible error, defined here as a 10% decrease in method performance.
Show less - Date Issued
- 2014
- Identifier
- CFH0004658, ucf:45288
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004658
- Title
- STRUCTURAL HEALTH MONITORING OF A STADIUM FOR EVALUATING HUMAN COMFORT AND STRUCTURAL PERFORMANCE.
- Creator
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Sazak, Hasan, Catbas, F. Necati, University of Central Florida
- Abstract / Description
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Light and rapid constructions as well as considerations such as improved line of sight and increased capacity for modern stadium structures make them vulnerable for vibration serviceability problems. These problems are also observed at convention centers, large shopping malls, concert halls and ballrooms. Especially when the individuals in a crowd are involved in some sort of coordinated motion, this type of loading creates the most potential for high levels of vibration. In order to...
Show moreLight and rapid constructions as well as considerations such as improved line of sight and increased capacity for modern stadium structures make them vulnerable for vibration serviceability problems. These problems are also observed at convention centers, large shopping malls, concert halls and ballrooms. Especially when the individuals in a crowd are involved in some sort of coordinated motion, this type of loading creates the most potential for high levels of vibration. In order to understand the causes of vibration, vibration levels, service and safety levels, Structural Health Monitoring (SHM) can be implemented to track and evaluate performance of a structure during events such as games at football stadia. SHM becomes a critical need especially when decisions such as repair and retrofit are to be made for the structure. The main objectives of this study are a) to determine the impact of vibration to human comfort levels; b) to identify dynamic loading for the coordinated motion; c) to determine the structural performance by means of a detailed model validated using experimental data. In order to achieve these objectives, a football stadium was monitored for three years to establish the vibration levels during different games and different events in each game such as goals, interceptions, playing a particular song. It is seen that certain events and long periods of playing particular songs induced vibration levels that are at the threshold of human comfort based on the design codes. To simulate the crowd motion due to this song, a laboratory study was designed and conducted to experimentally determine the forcing functions due to jumping with the rhythm of the song. The spectral analysis of the stadium data and the song also revealed that the first mode frequency of the stadium and the dominant frequency of the music are very close, creating resonance conditions. Further investigative studies were conducted by developing a finite element (FE) model of the stadium, which was validated using the results of the modal analysis from the ambient vibration data. Subsequently, the FE model was employed to simulate forcing functions obtained from the laboratory studies to explore the vibration levels, dynamic response as well as the response of the structure when it is retrofitted by additional elements. In addition, different aspects of model development, with respect to the physical model of the stadium were outlined in terms of design considerations, instrumentation, finite element modeling, and simulating dynamic effect of spectators. Finally, the effectiveness of the retrofit by adding elements to the steel structure of the stadium was explored by simulating the crowd motion with the FE model.
Show less - Date Issued
- 2010
- Identifier
- CFE0003387, ucf:48470
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003387
- Title
- PHYSICAL PROPERTIES OF WAVE SCATTERING BY CHIRAL PERIODIC STRUCTURE.
- Creator
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Yang, Xiaomin, Wu, Xinzhang, University of Central Florida
- Abstract / Description
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Attention has been focused on electromagnetic chirality and its potential applications to microwave, millimeter wave and optical wave devices. In this work, wave propagation through a chiral periodic structure with arbitrary shape is investigated. Although perturbation theory and coupled-mode theory have been used to analyze chiral periodic structure, those are approximate methods and can only be used for low frequency applications. In this work, the rigorous mode-matching method is used to...
Show moreAttention has been focused on electromagnetic chirality and its potential applications to microwave, millimeter wave and optical wave devices. In this work, wave propagation through a chiral periodic structure with arbitrary shape is investigated. Although perturbation theory and coupled-mode theory have been used to analyze chiral periodic structure, those are approximate methods and can only be used for low frequency applications. In this work, the rigorous mode-matching method is used to solve the problem. Staircase approximation is introduced to change the curved structure to a multilayer structure. The field solutions in the uniform air regions and unbounded air-chiral periodic array have been derived. Finite element method is used to solve the eigenvalues and eigenfunctions in the periodic chiral slabs. Mode-matching method is used at the boundaries to calculate the scattering characteristics. Numerical results are displayed to explain the underlying physical properties of the chiral periodic structure. The Wood's anomalies at high frequencies have been investigated and explained by the excitation of leaky waves guided along the periodic layer. The influence of frequency, chirality parameter, incident angle, curve shape and period are discussed. It has been found that the chiral periodic structure can be used as both a frequency selective device and a mode conversion device. First, the derivation and numeric calculation were done with the principal plane incidence. Then, the discussion was extended to the more general case of oblique incidence by the coordinate transformation.
Show less - Date Issued
- 2009
- Identifier
- CFE0002964, ucf:47987
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002964
- Title
- THE WAVE STRUCTURE FUNCTION AND TEMPORAL FREQUENCY SPREAD IN WEAK TO STRONG OPTICAL TURBULENCE.
- Creator
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Masino, Aaron Joseph, Young, Cynthia Y., University of Central Florida
- Abstract / Description
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This paper presents analytic expressions for the wave structure function, frequency spread of the temporal frequency spectrum, and the temporal frequency spectrum of optical signals propagating through a random medium, specifically the Earth's atmosphere. The results are believed to be valid for all optical turbulence conditions. These expressions are developed using the Rytov approximation method. Generally, the validity of statistical quantities obtained via this method is restricted to...
Show moreThis paper presents analytic expressions for the wave structure function, frequency spread of the temporal frequency spectrum, and the temporal frequency spectrum of optical signals propagating through a random medium, specifically the Earth's atmosphere. The results are believed to be valid for all optical turbulence conditions. These expressions are developed using the Rytov approximation method. Generally, the validity of statistical quantities obtained via this method is restricted to conditions of weak optical turbulence. However, in this work, by using a modification of the effective atmospheric spectral model presented by Andrews et al. for scintillation index, wave structure function expressions have been derived that are valid in all turbulence conditions as evidenced by comparison to experimental data. Analytic wave structure function results are developed for plane, spherical, and Gaussian-beam waves for one-way propagation. For the special case of a spherical wave, comparisons are made with experimental data. The double pass case is also considered. Analytic expressions for the wave structure function are given that incorporate reflection from a smooth target for an incident spherical wave. Additionally, analytic expressions for the frequency spread of the temporal frequency spectrum and the temporal frequency spectrum itself, after one-way propagation for horizontal and slant paths, are derived for plane and spherical waves. These results are also based on the Rytov perturbation method . Expressions that are believed to be valid in all turbulence conditions are also developed by use of the effective atmospheric spectral model used in the wave structure function development. Finally, double pass frequency spread expressions are also presented. As in the case of the wave structure function, reflection from a smooth target with an incident spherical wave is considered.
Show less - Date Issued
- 2004
- Identifier
- CFE0000073, ucf:46106
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000073
- Title
- CHARACTERIZATION OF CRITICAL NETWORK COMPONENTS OF COUPLED OSCILLATORS.
- Creator
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Holifield, Gregory, A. S. Wu, A. Gonzalez,, University of Central Florida
- Abstract / Description
-
This dissertation analyzes the fundamental limits for the determination of the network structure of loosely coupled oscillators based on observing the behavior of the network, specifically, node synchronization. The determination of the requisite characteristics and underlying behaviors necessary for the application of a theoretical mechanism for determining the underlying network topology in a network of loosely coupled natural oscillators are the desired outcome. To that end, this effort...
Show moreThis dissertation analyzes the fundamental limits for the determination of the network structure of loosely coupled oscillators based on observing the behavior of the network, specifically, node synchronization. The determination of the requisite characteristics and underlying behaviors necessary for the application of a theoretical mechanism for determining the underlying network topology in a network of loosely coupled natural oscillators are the desired outcome. To that end, this effort defines an analytical framework where key components of networks of coupled oscillators are isolated in order to determine the relationships between the various components. The relationship between the number of nodes in a network, the number of connections in the network, the number of connections of a given node, the distribution of the phases of the network, and the resolution of measurement of the components of the network, and system noise is investigated.
Show less - Date Issued
- 2006
- Identifier
- CFE0001452, ucf:47038
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001452
- Title
- POLYMER-DERIVED SI-AL-C-N CERAMICS:OXIDATION, HOT-CORROSION, AND STRUCTURAL EVOLUTION.
- Creator
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Wang, Yiguang, An, Linan, University of Central Florida
- Abstract / Description
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Polymer-derived ceramics are a new class of materials synthesized by thermal decomposition of polymer precursors. Previous studies have shown that the materials exhibit excellent thermo-mechanical properties and can be stable at temperatures up to 2000oC. Furthermore, the novel polymer-to-ceramics process enables the manipulation of the ceramic structures at the atomic/nano level by designing the chemistry of polymer precursors and controlling the pyrolysis conditions, thereby, the properties...
Show morePolymer-derived ceramics are a new class of materials synthesized by thermal decomposition of polymer precursors. Previous studies have shown that the materials exhibit excellent thermo-mechanical properties and can be stable at temperatures up to 2000oC. Furthermore, the novel polymer-to-ceramics process enables the manipulation of the ceramic structures at the atomic/nano level by designing the chemistry of polymer precursors and controlling the pyrolysis conditions, thereby, the properties of ceramics. In this dissertation, oxidation/hot-corrosion behavior and the structural evolution of Si-Al-C-N ceramics have been studied. The structural evolution and crystallization behavior of the SiCN and SiAlCN ceramics are investigated using FT-IR, XRD, and NMR. The results revealed that aluminum could greatly affect the structural evolution and crystallization behavior of polymer-derived ceramics, resulting to better stability. The oxidation kinetics of the SiCN and SiAlCN ceramics in air is determined by directly measuring the thickness of the oxide scale with SEM as a function of oxidation time. The results revealed that while the oxidation of the SiCN ceramics follows parabolic kinetics in all of the ranges of testing temperatures, oxidation of the SiAlCN ceramics is complicated: their oxidation rates are similar to that of SiCN ceramics at the earlier stage, but they decrease to very low levels after a certain time. The oxidation rate of the SiAlCN ceramics is more than an order of magnitude lower than any other silicon based ceramics previously reported. The transportation behavior of oxygen through the oxide scales is studied by 18O diffusion. The results indicate that oxidation is controlled by molecular oxygen diffusing through the oxides for both SiCN and SiAlCN ceramics; however, the oxygen diffusion rate in the oxides on SiAlCN ceramics is remarkably retarded. The structures of the oxides are characterized by XRD and NMR. A structural model is advanced to account for the aluminum effect on the oxygen diffusion in the oxide. The oxidation and hot-corrosion kinetics of the SiCN and SiAlCN ceramics in water vapor are determined by measuring their weight changes as a function of annealing time. The kinetic constants, kp and kl, are obtained by fitting the weight-change data with a paralinear model. The results reveal that the SiAlCN ceramics have a much better corrosion resistance than the SiCN and CVD SiC/Si3N4. After annealing at 1400oC for 300 hours, the SiAlCN-20 still retains more than 70% of its original strength, while the SiCN only retains about 20% of its original strength. The improvement in oxidation/hot-corrosion resistance of the SiAlCN ceramics is attributed to the low activity of the SiO2 in the Al2O3-containing silica. In summary, I have developed a new class of high-temperature materials, Si-Al-C-N ceramics. It is demonstrated that these new materials have excellent oxidation and corrosion resistance and thermal stability. Together with their easy processability, the materials will find many high temperature applications such as environmental barrier coatings, ceramic matrix composites, and MEMS for harsh environments.
Show less - Date Issued
- 2006
- Identifier
- CFE0001017, ucf:46810
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001017
- Title
- IDENTIFYING FACTORS THAT INFLUENCE GENDER DISPARITIES IN PHYSICIAN INCOME: IMPLICATIONS FOR PUBLIC POLICY.
- Creator
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Bolyard, Wendy, Wan, Thomas, University of Central Florida
- Abstract / Description
-
Research has shown that female physicians continue to earn less than their male counterparts. From both social justice and feminist perspectives, laws requiring equal pay should provide just income for females as compared to males. However, the literature continues to indicate that in general females earn less than males, a trend that is also true for physicians. Theoretically informed postulates are measured here with structural equation modeling to test the influence of the unique latent...
Show moreResearch has shown that female physicians continue to earn less than their male counterparts. From both social justice and feminist perspectives, laws requiring equal pay should provide just income for females as compared to males. However, the literature continues to indicate that in general females earn less than males, a trend that is also true for physicians. Theoretically informed postulates are measured here with structural equation modeling to test the influence of the unique latent construct "specialization" on the income gap while controlling for demographic and contextual variables. The analysis tests the assumption that the influence of specialization is the same for females and males. If the influence of specialization and other variables differs by gender, gender bias in physician income may be conceptually implied. The study uses three waves of data from the Community Tracking Study Physician Survey (CTS). The study finds an income gap between females and males in three waves of the CTS. Gini coefficients show females continue to experience greater income inequality than males, with the Lorenz curves for males being closer to the equality lines. Using 1999 income data, there is a statistically significant income gap between female and male physicians when controlling for weeks worked. Information Technology (IT) use was found to be the most reliable construct measuring the unique latent variable specialization. Structural equation modeling showed indicators of specialization have an influence on the income gap. The variables in the CTS Physician Survey made for a poor construct that failed to measure specialization as a uni-dimensional construct. The variables that influence the income gap were different for females than for males. As policy makers revise or create better laws to protect income equality, gender differences must be taken into consideration.
Show less - Date Issued
- 2006
- Identifier
- CFE0001245, ucf:46909
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001245
- Title
- STRUCTURE DIFFERENCE AND IMPLICATION TO ASSEMBLY MORPHOLOGY CONTROL OF ROUS SARCOMA VIRUS CAPSID PROTEIN.
- Creator
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Hastings, John, Chen, Bo, University of Central Florida
- Abstract / Description
-
Rous Sarcoma Virus (RSV) is an avian retrovirus with an enclosing capsid protein (CA) shell. RSV CA is studied due to its similar molecular structure to other retrovirus capsid proteins such as Human Immunodeficiency Virus (HIV). In this project, turbidity assay is used to track the assembly process of RSV CA, while solid state nuclear magnetic resonance (ssNMR) is used to probe the CA structure at a site specific level and investigate the morphology of the spherical structure of the I190V...
Show moreRous Sarcoma Virus (RSV) is an avian retrovirus with an enclosing capsid protein (CA) shell. RSV CA is studied due to its similar molecular structure to other retrovirus capsid proteins such as Human Immunodeficiency Virus (HIV). In this project, turbidity assay is used to track the assembly process of RSV CA, while solid state nuclear magnetic resonance (ssNMR) is used to probe the CA structure at a site specific level and investigate the morphology of the spherical structure of the I190V mutated strain of RSV CA. The I190V mutant is a naturally occurring mutation and is able to form into roughly uniform spheres, where the wild type RSV CA cannot form as pure spheres as possible. Turbidity assay results of the mutated RSV CA revealed a lack of a noticeable lag time before assembly began, as well as, a prolonged time period to reach saturation when compared to the wild-type RSV CA. Using ssNMR, and the TALOS-N program the torsion angles of the protein backbone were found. Using Ramachandran plots, it was found that the mutation of the 190th residue from Isoleucine to Valine caused a changed in the secondary structure of residues, from ?-helix to ?-sheet and vice versa. These changes were concentrated at the loops between select interfaces of helices that make up the structure of RSV CA. In particular, between helices 4 (residues 65-85), 8 (residues 165-177), and 11 (residues 215-225). The differing secondary structure in the mutant RSV CA was supported by the overlaying of the NMR spectra of the wild-type RSV CA on to the spherically assembled mutant RSV CA. It can be concluded that the spherical assembly of the mutated RSV CA displays noticeable differences in assembly and overall structure when compared to the wild-type RSV CA.
Show less - Date Issued
- 2019
- Identifier
- CFH2000458, ucf:45705
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000458
- Title
- COMPUTATIONAL HURRICANE HAZARD ANALYSIS-A PERFORMANCE BASED ENGINEERING VIEW.
- Creator
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Vanek, Christopher, Mackie, Kevin, University of Central Florida
- Abstract / Description
-
Widespread structural damage to critical facilities such as levees, buildings, dams and bridges during hurricanes has exemplified the need to consider multiple hazards associated with hurricanes as well as the potential for unacceptable levels of performance even if failure is not observed. These inadequate standards warrant the use of more accurate methods to describe the anticipated structural response, and damage for extreme events often termed performance based engineering (PBE)....
Show moreWidespread structural damage to critical facilities such as levees, buildings, dams and bridges during hurricanes has exemplified the need to consider multiple hazards associated with hurricanes as well as the potential for unacceptable levels of performance even if failure is not observed. These inadequate standards warrant the use of more accurate methods to describe the anticipated structural response, and damage for extreme events often termed performance based engineering (PBE). Therefore PBE was extended into the field of hurricane engineering in this study. Application of performance-based principles involves collection of the numerous hazards data from sources such as historical records, laboratory experiments or stochastic simulations. However, the hazards associated with a hurricane typically include spatial and temporal variation therefore, more detailed collection of data from each hazard of this loading spectrum is required. At the same time, computational power and computer-aided design have advanced and potentially allows for collection of the structure-specific hazard data. This novel technique, known as computational fluid dynamics (CFD), was applied to the wind and wave hazards associated with hurricanes to accurately quantify the spectrum of dynamic loads in this study. Numerical simulation results are presented on verification of this technique with laboratory experimental studies and further application to a typical Florida building and bridge prototype. Both the time and frequency domain content of random process signals were analyzed and compared through basic properties including the spectral density, autocorrelation, and mean. Following quantification of the dynamic loads on each structure, a detailed structural FEM was constructed of each structure and response curves were created for various levels of hurricane categories. Results show that both the time and frequency content of the dynamic signal could be accurately captured through CFD simulations in a much more cost effective manner than laboratory experimentation. Structural FEM models showed the poor performance of two coastal structures designed using deterministic principles, as serviceability and strength limit states were exceeded. Additionally, the response curves created for the prototype structure could be further developed for multiple wind directions and wave periods. Thus CFD is a viable option to wind and wave laboratory studies and a key tool for the development of PBE in the field of hurricane engineering.
Show less - Date Issued
- 2010
- Identifier
- CFE0003491, ucf:48963
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003491
- Title
- Recidivism Measurement and Sanction Effectiveness in Youth Diversion Programs.
- Creator
-
Maroney, Thomas, Wan, Thomas, Sanborn, Joseph, Wolf, Ross, Zhang, Ning, University of Central Florida
- Abstract / Description
-
With the rapid growth of juvenile offender diversion programs, which use many non-traditional sanctions, the effectiveness of sanction combinations in juvenile diversion programs and in each individual program needs to be evaluated. Those making sanctioning decisions currently do so based on intuition rather than using an evidence- or theory-based approach. Considerable research has examined the relationship between offender risk factors and recidivism (who is more likely to reoffend?) and...
Show moreWith the rapid growth of juvenile offender diversion programs, which use many non-traditional sanctions, the effectiveness of sanction combinations in juvenile diversion programs and in each individual program needs to be evaluated. Those making sanctioning decisions currently do so based on intuition rather than using an evidence- or theory-based approach. Considerable research has examined the relationship between offender risk factors and recidivism (who is more likely to reoffend?) and between offender risk factors and sanctions (who is more likely to receive what sanctions?), but little is known about the relationship between sanctions and recidivism (which sanctions best reduce recidivism and for whom?). Furthermore, recidivism studies vary drastically in how they measure or quantify recidivism. This variability of approach makes comparing studies difficult and provides a less-than-complete picture of recidivism in general. The present study used data from one specific youth diversion program to test certain hypotheses of sanctioning by developing and testing a model for assigning sanction combinations to certain offenders on the basis of their individual characteristics. The study first developed measurement models for Offender Risk Propensity, Multiplicity of Sanctions, and Recidivism using structural equation modeling (SEM). Then predictive models were developed to test specific relationships. Understanding the effectiveness of certain sanction packages on certain offenders can form the basis for effective sanctioning in youth diversion programs. This study sought to answer three research questions: What is the best way to measure recidivism? Does completion of a restorative justice program reduce recidivism? Which sanctions, if any, reduce recidivism for specific offender types? To answer the first question: a multi-indicator latent construct of recidivism did a very good job of measuring variation in recidivism. Multiple indicators analyzed simultaneously produced a robust tool that can be used in other recidivism studies and help to reduce comparability issues between studies. The recidivism construct, when tested as a function of completion of the restorative justice program, was seen to produce a significant model having an overall good fit with the data. Thus to answer the second research question: offenders' completion status for the restorative justice program was shown to be a significant predictor of the latent construct of recidivism at the 0.05 level (two-tailed), with those who failed to complete (or chose not to participate) having higher recidivism than did those who completed the program. To answer the third research question: the assignment of specific sanctions (both those suggested by research and theory and those traditionally assigned by this and similar programs) on the entire data set (and on various subsets) of this study have no statistically significant impact on recidivism at the 0.05 level (two tailed).The findings suggest many policy implications. Consistency is all but nonexistent in recidivism measurements in the academic literature and in program review studies. A multi-indicator latent construct of recidivism, such as the one proposed and proven effective in this study, provides a more complete picture than simply conceptualizing recidivism by one dummy variable. This recidivism model can be used as the endogenous variable to evaluate programs and their practices and could reduce the problem of study comparability. This could lead to a better understanding of program characteristics and their impact on offender success. This study also found that completion of the Neighborhood Restorative Justice Program was a significant predictor of recidivism, yet none of the eleven most commonly assigned sanctions were seen to have a significant impact on recidivism for any subgroup. Proponents of restorative justice argue that it is the programs' characteristics and not their specific activities that make the programs successful. Reintegrative Shaming Theory and Labeling Theory support this claim and suggest the best approach to address youth criminal behavior is to admonish the act and not the actor, have the offender and community agree on a plan to make the community whole after that criminal act, and prevent repeated interaction with the formal criminal justice system which encourages the youth to see themself as a deviant and engage in further deviant behavior. These characteristics should be further examined and widely employed if confirmed.
Show less - Date Issued
- 2012
- Identifier
- CFE0004406, ucf:49392
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004406
- Title
- Employing Quality Management Principles to Improve the Performance of Educational Systems: An Empirical Study of the Effect of ISO 9001 Standard on Teachers and Administrators Performance in the Indonesian Vocational Education System.
- Creator
-
Kuncoro, Andreas, Elshennawy, Ahmad, Lee, Gene, Rabelo, Luis, Bai, Haiyan, University of Central Florida
- Abstract / Description
-
ISO 9001 has been world widely implemented in both manufacturing and service organizations. A lot of studies have been conducted to investigate the effects of ISO 9001 implementation on the performance of these organizations. Most of these studies show that ISO 9001 implementation realized positive operational improvements and financial success.Building on the merits of successful implementation of ISO 9001 quality management system in manufacturing and service, educational institutions have...
Show moreISO 9001 has been world widely implemented in both manufacturing and service organizations. A lot of studies have been conducted to investigate the effects of ISO 9001 implementation on the performance of these organizations. Most of these studies show that ISO 9001 implementation realized positive operational improvements and financial success.Building on the merits of successful implementation of ISO 9001 quality management system in manufacturing and service, educational institutions have been attempted to adopt it in their operations. Even though there are studies relating ISO implementation to education, no research has been done to investigate the effects of ISO 9001 at the individual level.The objective of this research is to investigate the effects of ISO 9001 quality management implementation on the performance of administrators and teachers. The Indonesian vocational education system is selected as a case example as there is a significant number of such institutions in Indonesia that attempt to achieve ISO certification and there is a national need to improve the performance of vocational education. It is a challenge to assess objectively the degree of ISO 9001 implementation in this specific educational context because of the size and diversity. This study relies on survey that measures the respondents' perception. Hence, this study applies a self-reported survey based performance measurement. The questionnaires are developed based on extensive literature review. Partial Least Squares Structural Equation Modeling (PLSSEM) has been used to examine the relationships between the different elements of quality management systems, quality culture; administrator and teacher performances. The study is able to examine multiple interrelated dependence and subsequent relationships simultaneously among examined factors such as teacher and administrator performance, existing quality culture and ISO principles; and to incorporate variables that cannot be directly measured, such as leadership, for example. The findings of this study show that ISO 9001 implementation has positive significant effect on the performance of the vocational school administrator and teacher. The study also identifies key influencing elements of the ISO quality management system and examines their direct and indirect relationships with teacher and administrator performances. This study is expected to improve the current practices in implementing ISO and quality culture in any educational settings, specifically in the case of vocational educational system.
Show less - Date Issued
- 2013
- Identifier
- CFE0005019, ucf:50006
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005019
- Title
- Comparison of Second Order Conformal Symplectic Schemes with Linear Stability Analysis.
- Creator
-
Floyd, Dwayne, Moore, Brian, Schober, Constance, Mohapatra, Ram, University of Central Florida
- Abstract / Description
-
Numerical methods for solving linearly damped Hamiltonian ordinary differential equations are analyzed and compared. The methods are constructed from the well-known St(&)#246;rmer-Verlet and implicit midpoint methods. The structure preservation properties of each method are shown analytically and numerically. Each method is shown to preserve a symplectic form up to a constantand are therefore conformal symplectic integrators, with each method shown to accurately preserve the rate of momentum...
Show moreNumerical methods for solving linearly damped Hamiltonian ordinary differential equations are analyzed and compared. The methods are constructed from the well-known St(&)#246;rmer-Verlet and implicit midpoint methods. The structure preservation properties of each method are shown analytically and numerically. Each method is shown to preserve a symplectic form up to a constantand are therefore conformal symplectic integrators, with each method shown to accurately preserve the rate of momentum dissipation. An analytical linear stability analysis is completed for each method, establishing thresholds between the value of the damping coefficient and the step-size that ensure stability. The methods are all second order and the preservation of the rate of energy dissipation is compared to that of a third order Runge-Kutta method that does not preserve conformal properties. Numerical experiments will include the damped harmonic oscillator and the damped nonlinear pendulum.
Show less - Date Issued
- 2014
- Identifier
- CFE0005793, ucf:50051
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005793
- Title
- Monitoring for Underdetermined Underground Structures during Excavation Using Limited Sensor Data.
- Creator
-
Mehdawi, Nader, Yun, Hae-Bum, Sallam, Amr, Chopra, Manoj, University of Central Florida
- Abstract / Description
-
A realistic field monitoring application to evaluate close proximity tunneling effects of a new tunnel on an existing tunnel is presented. A blind source separation (BSS)-based monitoring framework was developed using sensor data collected from the existing tunnel while the new tunnel was excavated. The developed monitoring framework is particularly useful to analyze underdetermined systems due to insufficient sensor data for explicit input force-output deformation relations. The analysis...
Show moreA realistic field monitoring application to evaluate close proximity tunneling effects of a new tunnel on an existing tunnel is presented. A blind source separation (BSS)-based monitoring framework was developed using sensor data collected from the existing tunnel while the new tunnel was excavated. The developed monitoring framework is particularly useful to analyze underdetermined systems due to insufficient sensor data for explicit input force-output deformation relations. The analysis results show that the eigen-parameters obtained from the correlation matrix of raw sensor data can be used as excellent indicators to assess the tunnel structural behaviors during the excavation with powerful visualization capability of tunnel lining deformation. Since the presented methodology is data-driven and not limited to a specific sensor type, it can be employed in various proximity excavation monitoring applications.
Show less - Date Issued
- 2013
- Identifier
- CFE0004718, ucf:49834
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004718
- Title
- First Principle Studies of Cu-Carbon Nanotube Hybrid Structures with Emphasis on the Electronic Structures and the Transport Properties.
- Creator
-
Yang, Chengyu, Chen, Quanfang, Leuenberger, Michael, Coffey, Kevin, Ishigami, Marsahir, Fang, Jiyu, University of Central Florida
- Abstract / Description
-
Carbon nanotubes have been regarded as ideal building blocks for nanoelectronics and multifunctional nanocomposites due to their exceptional strength, stiffness, flexibility, as well as their excellent electrical properties. However, carbon nanotube itself has limitations to fulfill the practical application needs: 1) an individual carbon nanotube has a low density of states at the Fermi level, and thus its conductivity is only comparable to moderate metals but lower than that of copper. 2)...
Show moreCarbon nanotubes have been regarded as ideal building blocks for nanoelectronics and multifunctional nanocomposites due to their exceptional strength, stiffness, flexibility, as well as their excellent electrical properties. However, carbon nanotube itself has limitations to fulfill the practical application needs: 1) an individual carbon nanotube has a low density of states at the Fermi level, and thus its conductivity is only comparable to moderate metals but lower than that of copper. 2) Metallic and semiconducting nanotubes are inherently mixed together from the synthesis, and the selection/separation is very difficult with very low efficiency. 3) Carbon nanotubes alone cannot be used in practical application and a bonding material is normally needed as the join material for actual devices. In this work, we fundamentally explored the possibility that metals (Cu, Al) could tailor carbon nanotube's electronic structure and even transit it from semiconducting to metallic, thus skipping the selection between the metallic and the semiconducting CNTs. We also found out a novel way to enhance a semiconducting CNT system's conductance even better than that of a metallic CNT system. All these researches are done under density functional theory (DFT) frame in conjunction with non-equilibrium Green functions (NEGF).At first we studied the adsorbed copper's influence on the electronic properties of CNT (10, 0) and CNT (5, 5). Results indicate that both the Density of States (DOS) and the transmission coefficients of CNT (5,5) /Cu have been increased. For CNT (10,0)/Cu, the band gap has been shrank, which means the improved conducting properties by the incorporation of copper . As a further case, semiconductor SWCNT (10, 0) with more adsorbed copper chains outside has been studied. 1, 4, 5 and 6 Cu chains have been added onto the carbon nanotube (10,0), and the adsorption of 6 Cu chains finally lead to the transform of the system from semiconducting to metallic. Considering the confining effect, the case that Cu filled into CNT (10, 0) is also studied. It is found that the filled copper chains could modify the system to be metallic more efficiently than the adsorbed Cu chain. Similarly, Al adsorbed on CNT (10, 0) is also studied, and it is found that Al has a better efficiency than copper in tuning the semiconducting CNT to metallic. The existing chemical bonds between the CNT and Al atoms may account for this higher efficiency. In addition, the resultant conductivity of the Al/CNT system is better than that of Cu/CNT system. The Cu/CNT (5,5)+Cu/Cu junction, as another realistic device setup, has been studied in terms of the conductance. The results show that the incorporation of Cu would enhance the conductance of the Cu/CNT/Cu system due to the interaction between Cu and the CNT.
Show less - Date Issued
- 2013
- Identifier
- CFE0005280, ucf:50561
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005280
- Title
- PHOSPHOLIPASE A2MECHANISM OF INTERFACIAL ACTIVATION,AN INTERDISCLIPLINARY APPROACH.
- Creator
-
Nemec, Kathleen, Tatulian, Suren, University of Central Florida
- Abstract / Description
-
Phospholipase A2 (PLA2) is an enzyme that hydrolyzes the sn-2-ester bond of membrane phospholipids and liberates arachidonic acid, which is converted to eicosanoids that act as potent mediators of inflammation and allergy. As such this enzyme plays a crucial role in many homeostatic physiological and immunologic processes and disease progression. PLA2s undergo substantial increase in activity upon binding to cellular membranes. This effect of interfacial activation is well recognized, yet its...
Show morePhospholipase A2 (PLA2) is an enzyme that hydrolyzes the sn-2-ester bond of membrane phospholipids and liberates arachidonic acid, which is converted to eicosanoids that act as potent mediators of inflammation and allergy. As such this enzyme plays a crucial role in many homeostatic physiological and immunologic processes and disease progression. PLA2s undergo substantial increase in activity upon binding to cellular membranes. This effect of interfacial activation is well recognized, yet its structural and physical aspects are poorly understood. In this work, we have employed the interdisciplinary methods of molecular biology, biochemistry, biophysics, bioinformatics and computational biology, in order to elucidate the structure-function relationships mediating the interfacial activation of human group IIA and group IB PLA2 isoforms. We have evaluated the structural and functional consequences of two conservative, single residue substitutions, located at key membrane-binding and substrate-binding positions of hIIA PLA2. We have also evaluated a human group IB fragment (hIBdeltaN10), missing the first 10 N-terminal residues which make up the N-terminal alpha helix, as well as a chimeric enzyme substituting the N-terminal alpha helix of hIB PLA2 with that from hIIA PLA2 (hIIA/IB PLA2). We have compared the engineered proteins against both the hIIA and hIB PLA2 native enzymes and their N-terminal peptides, N10-hIB and N10-hIIA, respectively. We have developed and used a novel multidisciplinary approach in order to position the segmentally labeled hIB PLA2 and hIIA/IB chimeric PLA2s at the membrane surface. The results of this work provide significant insight into the understanding of the physical aspects of interfacial activation by determining the precise membrane binding modes of PLA2 isoforms and identifying certain amino acid residues and whole protein segments that play key roles in membrane binding, activation, and involved allosteric conformational effects in PLA2s.
Show less - Date Issued
- 2006
- Identifier
- CFE0001324, ucf:47015
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001324