Current Search: Topology (x)


Title

Optimization Analysis of a Simple Position Control System.

Creator

Cannon, Arthur G., Towle, Herbert C., Engineering

Abstract / Description

Florida Technological University College of Engineering Thesis; One of the problem areas of modern optimal control theory is the definition of suitable performance indices. This thesis demonstrates a rational method of establishing a quadratic performance index derived from a desired system model. Specifically, a first order model is used to provide a quadratic performance indix for which a second order system is optimized. Extension of the method to higher order systems, while requiring more...
Show moreFlorida Technological University College of Engineering Thesis; One of the problem areas of modern optimal control theory is the definition of suitable performance indices. This thesis demonstrates a rational method of establishing a quadratic performance index derived from a desired system model. Specifically, a first order model is used to provide a quadratic performance indix for which a second order system is optimized. Extension of the method to higher order systems, while requiring more computations, involves no additional theoretical complexities.
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Date Issued

1972

Identifier

CFR0012011, ucf:53085

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFR0012011


Title

The effect of electronhole pairs in semiconductor and topological insulator nanostructures on plasmon resonances and photon polarizations.

Creator

Paudel, Hari, Leuenberger, Michael, Rahman, Talat, Saha, Haripada, Gesquiere, Andre, University of Central Florida

Abstract / Description

The generation of electronhole pairs in materials has great importance. In directbandgap semiconductor materials, the mechanism of radiative recombination of electronholepairs leads to the emission of photons, which is the basis of Light Emitting Diodes(LEDs). The excitation of electronhole pairs by absorption of photons is the active processin photodiodes, solar cells, and other semiconductor photodetector devices. In optoelectronicdevices such as optical switches which are based on...
Show moreThe generation of electronhole pairs in materials has great importance. In directbandgap semiconductor materials, the mechanism of radiative recombination of electronholepairs leads to the emission of photons, which is the basis of Light Emitting Diodes(LEDs). The excitation of electronhole pairs by absorption of photons is the active processin photodiodes, solar cells, and other semiconductor photodetector devices. In optoelectronicdevices such as optical switches which are based on transmission and reflection of the photons,electronhole pairs excitation is a key for the device performance. Diodes and transistorsare also great discoveries in electronics which rely on the generation and recombination ofelectronhole pairs at pn junctions. In threedimensional topological insulators (3D TIs)materials nanostructures excitation of electronhole pairs can be utilized for the quantummemory, quantum information and quantum teleportation. In twodimensional (2D) layeredmaterials like graphene, MoS_2, MoSe_2, WS_2 and WSe_2 generation and recombination ofelectron hole pairs is main process at pn junctions, infrared detectors and sensors.This PhD thesis is concerned with the physics of different types of electronhole pairsin various materials, such as widebandgap semiconductors, 3D topological insulators, andplasmonic excitations in metallic nanostructures. The materials of interest are wide bandgap semiconductors such as TiO_2 , 3D TIs such as Pb_1?xSn_xTe and the 2D layered materials such as MoS_2 and MoO_3. We study the electronic and optical properties in bulk and nanostructures and find applications in the area of semiclassical and quantum information processing. One of the interesting applications we focus in this thesis is shift in surface plasmon resonance due to reduction in index of refraction of surrounding dielectric environment which inturns shifts the wavelength of surface plasmon resonance up to 125 nm for carrier density of10^22/cm^3. Employing this effect, we present a model of a light controlled plasmon switching using a hybrid metaldielectric heterostructures.In 3D TIs nanostructures, the time reversible spin partners in the valence and conductionband can be coupled by a left and a right handed circular polarization of the light.Such coupling of light with electronhole pair polarization provides an unique opportunityto utilize 3D TIs in quantum information processing and spintronics devices. We present a model of a 3D TI quantum dot made of spherical corebulk heterostructure. When a 3D TI QD is embedded inside a cavity, the singlephoton Faraday rotation provides the possibility to implement optically mediated quantum teleportation and quantum information processing with 3D TI QDs, where the qubit is defined by either an electronhole pair, a single electron spin, or a single hole spin in a 3D TI QD.Due to excellent transport properties in single and multiple layers of 2D layeredmaterials, several efforts have demonstrated the possibility to engineer electronic and optoelectronic devices based on MoS_2. In this thesis, we focus on theoretical and experimental study of electrical property and photoluminescence tuning, both in a singlelayer of MoS_2.We present theoretical analysis of experimental results from the point of view of stability of MoO_3 defects in MoS_2 single layer and bandstructures calculation. In experiment, the electrical property of a single layer of MoS_2 can be tuned from semiconducting to insulating regime via controlled exposure to oxygen plasma. The quenching of photoluminescence of asingle sheet of MoS_2 has also been observed upon exposure to oxygen plasmas. We calculatethe direct to indirect band gap transitions by going from MoS_2 single sheet to MoO_3 singlesheet during the plasma exposure, which is due to the formation of MoO_3 rich defect domainsinside a MoS_2 sheet.
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Date Issued

2014

Identifier

CFE0005397, ucf:50454

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0005397


Title

THE USE OF FILTERS IN TOPOLOGY.

Creator

Dasser, Abdellatif, Richardson, Gary, University of Central Florida

Abstract / Description

Sequences are sufficient to describe topological properties in metric spaces or, more generally, topological spaces having a countable base for the topology. However, filters or nets are needed in more abstract spaces. Nets are more natural extension of sequences but are generally less friendly to work with since quite often two nets have distinct directed sets for domains. Operations involving filters are set theoretic and generally certain to filters on the same set. The concept of a filter...
Show moreSequences are sufficient to describe topological properties in metric spaces or, more generally, topological spaces having a countable base for the topology. However, filters or nets are needed in more abstract spaces. Nets are more natural extension of sequences but are generally less friendly to work with since quite often two nets have distinct directed sets for domains. Operations involving filters are set theoretic and generally certain to filters on the same set. The concept of a filter was introduced by H. Cartan in 1937 and an excellent treatment of the subject can be found in N. Bourbaki (1940).
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Date Issued

2004

Identifier

CFE0000202, ucf:46271

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0000202


Title

CATEGORICAL PROPERTIES OF LATTICEVALUED CONVERGENCE SPACES.

Creator

Flores, Paul, Richardson, Gary, University of Central Florida

Abstract / Description

This work can be roughly divided into two parts. Initially, it may be considered a continuation of the very interesting research on the topic of LatticeValued Convergence Spaces given by Jäger [2001, 2005]. The alternate axioms presented here seem to lead to theorems having proofs more closely related to standard arguments used in Convergence Space theory when the Lattice is L=.Various Subcategories are investigated. One such subconstruct is shown to be isomorphic to the category of...
Show moreThis work can be roughly divided into two parts. Initially, it may be considered a continuation of the very interesting research on the topic of LatticeValued Convergence Spaces given by Jäger [2001, 2005]. The alternate axioms presented here seem to lead to theorems having proofs more closely related to standard arguments used in Convergence Space theory when the Lattice is L=.Various Subcategories are investigated. One such subconstruct is shown to be isomorphic to the category of Lattice Valued Fuzzy Convergence Spaces defined and studied by Jäger . Our principal category is shown to be a topological universe and contains a subconstruct isomorphic to the category of probabilistic convergence spaces discussed in Kent and Richardson when L=. Fundamental work in latticevalued convergence from the more general perspective of monads can be found in Gähler . Secondly, diagonal axioms are defined in the category whose objects consist of all the lattice valued convergence spaces. When the latter lattice is linearly ordered, a diagonal condition is given which characterizes those objects in the category that are determined by probabilistic convergence spaces which are topological. Certain background information regarding filters, convergence spaces, and diagonal axioms with its dual are given in Chapter 1. Chapter 2 describes Probabilistic Convergence and associated Diagonal axioms. Chapter 3 defines Jäger convergence and proves that Jäger's construct is isomorphic to a bireflective subconstruct of SLCS. Furthermore, connections between the diagonal axioms discussed and those given by Gähler are explored. In Chapter 4, further categorical properties of SLCS are discussed and in particular, it is shown that SLCS is topological, cartesian closed, and extensional. Chapter 5 explores connections between diagonal axioms for objects in the sub construct δ(PCS) and SLCS. Finally, recommendations for further research are provided.
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Date Issued

2007

Identifier

CFE0001715, ucf:47292

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0001715


Title

A NONISOLATED HALF BRIDGE BUCKBASED CONVERTER FOR VRM APPLICATION AND SMALL SIGNAL MODELING OF A NONCONVENTIONAL TWO PHASE BUCK.

Creator

Batarseh, Majd, Batarseh, Issa, University of Central Florida

Abstract / Description

The challenges imposed on Voltage Regulator Modules (VRM) become difficult to be achieved with the conventional multiphase buck converter commonly used on PC motherboards. For faster data transfer, a decrease in the output voltage is needed. This decrease causes small duty cycle that is accompanied by critical problems which impairs the efficiency. Therefore, these problems need to be addressed. Transformerbased nonisolated topologies are not new approaches to extend the duty cycle and...
Show moreThe challenges imposed on Voltage Regulator Modules (VRM) become difficult to be achieved with the conventional multiphase buck converter commonly used on PC motherboards. For faster data transfer, a decrease in the output voltage is needed. This decrease causes small duty cycle that is accompanied by critical problems which impairs the efficiency. Therefore, these problems need to be addressed. Transformerbased nonisolated topologies are not new approaches to extend the duty cycle and avoid the associated drawbacks. High leakage, several added components and complicated driving and control schemes are some of the tradeoffs to expand the duty cycle. The objective of this work is to present a new dcdc buckbased topology, which extends the duty cycle with minimum drawbacks by adding two transformers that can be integrated to decrease the size and two switches with zero voltage switching (ZVS). Another issue addressed in this thesis is deriving a small signal model for a twoinput twophase buck converter as an introduction to a new evolving field of multiinput converters.
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Date Issued

2006

Identifier

CFE0001513, ucf:47130

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0001513


Title

CONTROL AND TOPOLOGY IMPROVEMENTS IN HALFBRIDGE DCDC CONVERTERS.

Creator

Deng, Songquan, Batarseh, Issa, University of Central Florida

Abstract / Description

Efficiency and transient response are two key requirements for DCDC converters. Topology and control are two key topics in this dissertation. A variety of techniques for DCDC converter performance improvement are presented in this work. Focusing on the efficiency issue, a variety of clamping techniques including both active and passive methods are presented after the ringing issues in DCDC converters are investigated. By presenting the clamping techniques, a big variety of energy...
Show moreEfficiency and transient response are two key requirements for DCDC converters. Topology and control are two key topics in this dissertation. A variety of techniques for DCDC converter performance improvement are presented in this work. Focusing on the efficiency issue, a variety of clamping techniques including both active and passive methods are presented after the ringing issues in DCDC converters are investigated. By presenting the clamping techniques, a big variety of energy management concepts are introduced. The active bridgecapacitor tank clamping and FETdiodecapacitor tank clamping are close ideas, which transfer the leakage inductor energy to clamping capacitor to prevent oscillation between leakage inductor and junction capacitor of MOSFETs. The twoFETclamping tank employs two MOSFETs to freewheeling the leakage current when the main MOSFETs of the halfbridge are both off. Driving voltage variation on the secondary side Synchronous Rectifier (SR) MOSFETs in selfdriven circuit due to input voltage variation in bus converter applications is also investigated. One solution with a variety of derivations is proposed using zernercapacitor combination to clamping the voltage while maintaining reasonable power losses. Another efficiency improvement idea comes from phaseshift concept in DCDC converters. By employing phaseshift scheme, the primary side and the secondary side two MOSFETs have complementary driving signals respectively, which allow the MOSFET to be turned on with Zero Voltage Switching (ZVS). Simulation verified the feasibility of the proposed phaseshifted DCDC converter. From the control scheme point of view, a novel peak current mode control concept for halfbridge topologies is presented. Aiming at compensating the imbalanced voltage due to peak current mode control in symmetric halfbridge topologies, an additional voltage compensation loop is used to bring the halfbridge capacitor voltage back to balance. In the proposed solutions, one scheme is applied on symmetric halfbridge topology and the other one is applied on Dutycycleshifted (DCS) halfbridge topology. Both schemes employ simple circuitry and are suitable for integration. Loop stability issues are also investigated in this work. Modeling work shows the uncompensated halfbridge topology cannot be stabilized under all conditions and the additional compensation loop helps to prevent the voltage imbalance effectively.
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Date Issued

2005

Identifier

CFE0000840, ucf:46674

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0000840


Title

Membrane topology of a broadspectrum resistance factor responsible for lipid modification in Enterococcus faecium.

Creator

Harrison, Jesse, Roy, Herve, Teter, Kenneth, Phanstiel, Otto, University of Central Florida

Abstract / Description

Aminoacylphosphatidylglycerol synthases (aaPGSs) are integral membrane proteins that use aminoacyltRNAs as substrates to catalyze the addition of amino acids to phosphatidylglycerol (PG) in the cytoplasmic membranes of bacteria. Addition of amino acids to PG decreases the net negative charge of the membrane, conferring resistance to various classes of antibacterial agents (i.e., cationic antimicrobial peptides, betalactams, glycopeptides, and lipopeptides) and protecting the cell against...
Show moreAminoacylphosphatidylglycerol synthases (aaPGSs) are integral membrane proteins that use aminoacyltRNAs as substrates to catalyze the addition of amino acids to phosphatidylglycerol (PG) in the cytoplasmic membranes of bacteria. Addition of amino acids to PG decreases the net negative charge of the membrane, conferring resistance to various classes of antibacterial agents (i.e., cationic antimicrobial peptides, betalactams, glycopeptides, and lipopeptides) and protecting the cell against osmotic stress and acidic conditions. aaPGS homologs are found in a variety of clinically relevant microorganisms, including Enterococcus faecium, which is increasingly found to be the etiologic agent of antibioticresistant nosocomial infections. Although the broad distribution of these virulence factors across bacterial species makes them attractive targets for therapeutic strategies, little is known about the structure of aaPGSs. Two aaPGS paralogs are found in E. faecium, one of which exhibits relaxed substrate specificity and is responsible for the transfer of Arg (R), Ala (A), and Lys (K) to PG (RakPGS). The catalytic site of RakPGS is located in the hydrophilic Cterminal domain, which is localized in the cytoplasm. The Nterminus contains an integral membrane domain that is thought to harbor flippase activity that translocates the neosynthesized aaPG from the inner to the outer leaflet of the membrane. We are currently developing the substituted cysteine accessibility method (SCAM) and a dualreporter fusion system, which exploits alkaline phosphatase (Pho) and ?galactosidase (LacZ) activities, for investigating the membrane topology of RakPGS in E. faecium.
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Date Issued

2015

Identifier

CFE0006318, ucf:51566

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0006318


Title

THEORETICAL AND NUMERICAL STUDIES OF PHASE TRANSITIONS AND ERROR THRESHOLDS IN TOPOLOGICAL QUANTUM MEMORIES.

Creator

Jouzdani, Pejman, Mucciolo, Eduardo, Chang, Zenghu, Leuenberger, Michael, Abouraddy, Ayman, University of Central Florida

Abstract / Description

This dissertation is the collection of a progressive research on the topic of topological quantum computation and information with the focus on the error threshold of the wellknown models such as the unpaired Majorana, the toric code, and the planar code.We study the basics of quantum computation and quantum information, and in particular quantum error correction. Quantum error correction provides a tool for enhancing the quantum computation fidelity in the noisy environment of a real world....
Show moreThis dissertation is the collection of a progressive research on the topic of topological quantum computation and information with the focus on the error threshold of the wellknown models such as the unpaired Majorana, the toric code, and the planar code.We study the basics of quantum computation and quantum information, and in particular quantum error correction. Quantum error correction provides a tool for enhancing the quantum computation fidelity in the noisy environment of a real world. We begin with a brief introduction to stabilizer codes. The stabilizer formalism of the theory of quantum error correction gives a welldefined description of quantum codes that is used throughout this dissertation. Then, we turn our attention to a quite new subject, namely, topological quantum codes. Topological quantum codes take advantage of the topological characteristics of a physical manybody system. The physical manybody systems studied in the context of topological quantum codes are of two essential natures: they either have intrinsic interaction that selfcorrects errors, or are actively corrected to be maintainedin a desired quantum state. Examples of the former are the toric code and the unpaired Majorana, while an example for the latter is the surface code.A brief introduction and history of topological phenomena in condensed matter is provided. The unpaired Majorana and the Kitaev toy model are briefly explained. Later we introduce a spin model that maps onto the Kitaev toy model through a sequence of transformations. We show how this model is robust and tolerates local perturbations. The research on this topic, at the time of writing this dissertation, is still incomplete and only preliminary results are represented.As another example of passive error correcting codes with intrinsic Hamiltonian, the toric code is introduced. We also analyze the dynamics of the errors in the toric code known as anyons. We show numerically how the addition of disorder to the physical system underlying the toric code slows down the dynamics of the anyons. We go further and numerically analyze the presence of timedependent noise and the consequent delocalization of localized errors.The main portion of this dissertation is dedicated to the surface code. We study the surface code coupled to a noninteracting bosonic bath. We show how the interaction between the code and the bosonic bath can effectively induce correlated errors. These correlated errors may be corrected up to some extend. The extension beyond which quantum error correction seems impossible is the error threshold of the code. This threshold is analyzed by mapping the effective correlated error model onto a statistical model. We then study the phase transition in the statistical model. The analysis is in two parts. First, we carry out derivation of the effective correlated model, its mapping onto a statistical model, and perform an exact numerical analysis. Second, we employ a Monte Carlo method to extend the numerical analysis to large system size.We also tackle the problem of surface code with correlated and singlequbit errors by an exact mapping onto a twodimensional Ising model with boundary fields. We show how the phase transition point in one model, the Ising model, coincides with the intrinsic error threshold of the other model, the surface code.
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Date Issued

2014

Identifier

CFE0005512, ucf:50314

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0005512


Title

Functional Scaffolding for Musical Composition: A New Approach in ComputerAssisted Music Composition.

Creator

Hoover, Amy, Stanley, Kenneth, Wu, Annie, Laviola II, Joseph, Anderson, Thaddeus, University of Central Florida

Abstract / Description

While it is important for systems intended to enhance musical creativity to define and explore musical ideas conceived by individual users, many limit musical freedom by focusing on maintaining musical structure, thereby impeding the user's freedom to explore his or her individual style. This dissertation presents a comprehensive body of work that introduces a new musical representation that allows users to explore a space of musical rules that are created from their own melodies. This...
Show moreWhile it is important for systems intended to enhance musical creativity to define and explore musical ideas conceived by individual users, many limit musical freedom by focusing on maintaining musical structure, thereby impeding the user's freedom to explore his or her individual style. This dissertation presents a comprehensive body of work that introduces a new musical representation that allows users to explore a space of musical rules that are created from their own melodies. This representation, called functional scaffolding for musical composition (FSMC), exploits a simple yet powerful property of multipart compositions: The pattern of notes and rhythms in different instrumental parts of the same song are functionally related. That is, in principle, one part can be expressed as a function of another. Music in FSMC is represented accordingly as a functional relationship between an existing human composition, or scaffold, and an additional generated voice. This relationship is encoded by a type of artificial neural network called a compositional pattern producing network (CPPN). A human user without any musical expertise can then explore how these additional generated voices should relate to the scaffold through an interactive evolutionary process akin to animal breeding. The utility of this insight is validated by two implementations of FSMC called NEAT Drummer and MaestroGenesis, that respectively help users tailor drum patterns and complete multipart arrangements from as little as a single original monophonic track. The five major contributions of this work address the overarching hypothesis in this dissertation that functional relationships alone, rather than specialized music theory, are sufficient for generating plausible additional voices. First, to validate FSMC and determine whether plausible generated voices result from the humancomposed scaffold or intrinsic properties of the CPPN, drum patterns are created with NEAT Drummer to accompany several different polyphonic pieces. Extending the FSMC approach to generate pitched voices, the second contribution reinforces the importance of functional transformations through quality assessments that indicate that some partially FSMCgenerated pieces are indistinguishable from those that are fully human. While the third contribution focuses on constructing and exploring a space of plausible voices with MaestroGenesis, the fourth presents results from a twoyear study where students discuss their creative experience with the program. Finally, the fifth contribution is a plugin for MaestroGenesis called MaestroGenesis Voice (MGV) that provides users a more natural way to incorporate MaestroGenesis in their creative endeavors by allowing scaffold creation through the human voice. Together, the chapters in this dissertation constitute a comprehensive approach to assisted music generation, enabling creativity without the need for musical expertise.
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Date Issued

2014

Identifier

CFE0005350, ucf:50495

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0005350


Title

NoveltyAssisted Interactive Evolution of Control Behaviors.

Creator

Woolley, Brian, Stanley, Kenneth, Hughes, Charles, Gonzalez, Avelino, Wu, Annie, Hancock, Peter, University of Central Florida

Abstract / Description

The field of evolutionary computation is inspired by the achievements of natural evolution, in which there is no final objective. Yet the pursuit of objectives is ubiquitous in simulated evolution because evolutionary algorithms that can consistently achieve established benchmarks are lauded as successful, thus reinforcing this paradigm. A significant problem is that such objective approaches assume that intermediate stepping stones will increasingly resemble the final objective when in fact...
Show moreThe field of evolutionary computation is inspired by the achievements of natural evolution, in which there is no final objective. Yet the pursuit of objectives is ubiquitous in simulated evolution because evolutionary algorithms that can consistently achieve established benchmarks are lauded as successful, thus reinforcing this paradigm. A significant problem is that such objective approaches assume that intermediate stepping stones will increasingly resemble the final objective when in fact they often do not. The consequence is that while solutions may exist, searching for such objectives may not discover them. This problem with objectives is demonstrated through an experiment in this dissertation that compares how images discovered serendipitously during interactive evolution in an online system called Picbreeder cannot be rediscovered when they become the final objective of the very same algorithm that originally evolved them. This negative result demonstrates that pursuing an objective limits evolution by selecting offspring only based on the final objective. Furthermore, even when high fitness is achieved, the experimental results suggest that the resulting solutions are typically brittle, piecewise representations that only perform well by exploiting idiosyncratic features in the target. In response to this problem, the dissertation next highlights the importance of leveraging human insight during search as an alternative to articulating explicit objectives. In particular, a new approach called noveltyassisted interactive evolutionary computation (NAIEC) combines human intuition with a method called novelty search for the first time to facilitate the serendipitous discovery of agent behaviors. In this approach, the human user directs evolution by selecting what is interesting from the onscreen population of behaviors. However, unlike in typical IEC, the user can then request that the next generation be filled with novel descendants, as opposed to only the direct descendants of typical IEC. The result of such an approach, unconstrained by a priori objectives, is that it traverses key stepping stones that ultimately accumulate meaningful domain knowledge.To establishes this new evolutionary approach based on the serendipitous discovery of key stepping stones during evolution, this dissertation consists of four key contributions: (1) The first contribution establishes the deleterious effects of a priori objectives on evolution. The second (2) introduces the NAIEC approach as an alternative to traditional objectivebased approaches. The third (3) is a proofofconcept that demonstrates how combining human insight with novelty search finds solutions significantly faster and at lower genomic complexities than fullyautomated processes, including pure novelty search, suggesting an important role for human users in the search for solutions. Finally, (4) the NAIEC approach is applied in a challenge domain wherein leveraging human intuition and domain knowledge accelerates the evolution of solutions for the nontrivial octopusarm control task. The culmination of these contributions demonstrates the importance of incorporating human insights into simulated evolution as a means to discovering better solutions more rapidly than traditional approaches.
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Date Issued

2012

Identifier

CFE0004462, ucf:49335

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0004462


Title

LatticeValued TFilters and Induced Structures.

Creator

Reid, Frederick, Richardson, Gary, Brennan, Joseph, Han, Deguang, Lang, SheauDong, University of Central Florida

Abstract / Description

A complete lattice is called a frame provided meets distribute over arbitrary joins. The implication operation in this context plays a central role. Intuitively, it measures the degree to which one element is less than or equal to another. In this setting, a category is defined by equipping each set with a Tconvergence structure which is defined in terms of Tfilters. This category is shown to be topological, strongly Cartesian closed, and extensional. It is well known that the category of...
Show moreA complete lattice is called a frame provided meets distribute over arbitrary joins. The implication operation in this context plays a central role. Intuitively, it measures the degree to which one element is less than or equal to another. In this setting, a category is defined by equipping each set with a Tconvergence structure which is defined in terms of Tfilters. This category is shown to be topological, strongly Cartesian closed, and extensional. It is well known that the category of topological spaces and continuous maps is neither Cartesian closed nor extensional.Subcategories of compact and of complete spaces are investigated. It is shown that each Tconvergence space has a compactification with the extension property provided the frame is a Boolean algebra. TCauchy spaces are defined and sufficient conditions for the existence of a completion are given. Tuniform limit spaces are also defined and their completions are given in terms of the TCauchy spaces they induce. Categorical properties of these subcategories are also investigated. Further, for a fixed Tconvergence space, under suitable conditions, it is shown that there exists an order preserving bijection between the set of all strict, regular, Hausdorff compactifications and the set of all totally bounded TCauchy spaces which induce the fixed space.
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Date Issued

2019

Identifier

CFE0007520, ucf:52586

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0007520


Title

Experimental confirmation of ballistic nanofriction and quasiparticle interference in Dirac materials.

Creator

Lodge, Michael, Ishigami, Masahiro, Kaden, William, Schelling, Patrick, Del Barco, Enrique, Roy, Tania, University of Central Florida

Abstract / Description

This dissertation is broadly divided into two parts. The first part details the development and usage of an experimental apparatus to measure the dry nanofriction for a welldefined interface at high sliding speeds. I leverage the sensitivity of a quartz crystal microbalance (QCM) to determine the drag coefficient of an ensemble of gold nanocrystals sliding on graphene at speeds up to 11 cm/s. I discuss the theories of velocitydependent friction, especially at high sliding speeds, and QCM...
Show moreThis dissertation is broadly divided into two parts. The first part details the development and usage of an experimental apparatus to measure the dry nanofriction for a welldefined interface at high sliding speeds. I leverage the sensitivity of a quartz crystal microbalance (QCM) to determine the drag coefficient of an ensemble of gold nanocrystals sliding on graphene at speeds up to 11 cm/s. I discuss the theories of velocitydependent friction, especially at high sliding speeds, and QCM modeling. I also discuss our synthesis protocols for graphene and molybdenum disulfide, as well as our protocol for fabricating a clean, graphenelaminated QCM device and nanocrystal ensemble. The design and fabrication of our QCM oscillator circuit is presented in detail. The quantitativelymeasured the drag coefficient is compared against molecular dynamics simulations at both low and high sliding speeds. We show evidence of a predicted ultralow friction regime and find that the interaction energy between gold nanocrystals and graphene is lower than previously assumed. In the second part of this dissertation, I detail the band structure measurement of a novel semimetal using scanning tunneling microscopy. In particular, I measured the energydependenceof quasiparticle interference patterns at the surface of zirconium silicon sulfide (ZrSiS), a topological nodal line semimetal whose charge carrier quasiparticles possess a pseudospin degree offreedom. The aims of this study were to (1) discover the shape of the band structure above the Fermi level along a highsymmetry direction, (2) discover the energetic location of the line node inthe same highsymmetry direction, and (3) discover the selection rules for k transitions. This study confirms the predicted linearity in E(k) of the band structure above the Fermi level. Additionally,we observe an energydependent mechanism for pseudospin scattering. This study also provides the first experimentallyderived estimation of the line node position in E(k).
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Date Issued

2018

Identifier

CFE0007218, ucf:52222

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0007218


Title

Good Works: The Topoi of Corporate Social Responsibility in the Travel and Tourism Industry.

Creator

Culler, Connie, Scott, Blake, Jones, Dan, Rounsaville, Angela, Dingo, Rebecca, University of Central Florida

Abstract / Description

This dissertation focuses on the identification and analysis of Corporate Social Responsibility (CSR) topoi in the travel and tourism industry. A sample set of six companies was selected for the study due to their size and prominence in the industry  namely Disney, Hilton, Intercontinental, Marriott, Starwood, and Wyndham. Topoi were identified through a blended method of research that employed rhetorical analysis, modified grounded theory, and NVIVO content analysis software. The research...
Show moreThis dissertation focuses on the identification and analysis of Corporate Social Responsibility (CSR) topoi in the travel and tourism industry. A sample set of six companies was selected for the study due to their size and prominence in the industry  namely Disney, Hilton, Intercontinental, Marriott, Starwood, and Wyndham. Topoi were identified through a blended method of research that employed rhetorical analysis, modified grounded theory, and NVIVO content analysis software. The research followed three guiding principles to recognize textual cues and drive analysis: common and special topoi; topoi as heuristic; topoi for association and amplification; and topoi as fluid and movable. The common CSR topoi, triple bottom line and shared value, were also used as overarching categories for coding the texts. The results of the method yielded six unique topoi that were specific to each company; these included Inspiration, Higher Purpose, Collaborative Innovation, Leadership, The Age of Great Change, and Green. Results also included a set of seven special industry topoi that were common across all of the sample companies; these included Commitment, Management, Alignment, Environment, Engagement, Achievement, and Sustainability. The rhetorical synergy and topological levels identified through this research can inform other studies of CSR about the generative potential of topoi and its fluidity when viewed from different conceptual vantage points.
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Date Issued

2015

Identifier

CFE0005936, ucf:50851

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0005936


Title

Photon Statistics in Disordered Lattices.

Creator

Kondakci, Hasan, Saleh, Bahaa, Abouraddy, Ayman, Christodoulides, Demetrios, Mucciolo, Eduardo, University of Central Florida

Abstract / Description

Propagation of coherent waves through disordered media, whether optical, acoustic, or radio waves, results in a spatially redistributed random intensity pattern known as speckle  a statistical phenomenon. The subject of this dissertation is the statistics of monochromatic coherent light traversing disordered photonic lattices and its dependence on the disorder class, the level of disorder and the excitation configuration at the input. Throughout the dissertation, two disorder classes are...
Show morePropagation of coherent waves through disordered media, whether optical, acoustic, or radio waves, results in a spatially redistributed random intensity pattern known as speckle  a statistical phenomenon. The subject of this dissertation is the statistics of monochromatic coherent light traversing disordered photonic lattices and its dependence on the disorder class, the level of disorder and the excitation configuration at the input. Throughout the dissertation, two disorder classes are considered, namely, diagonal and offdiagonal disorders. The latter exhibits disorderimmune chiral symmetry  the appearance of the eigenmodes in skewsymmetric pairs and the corresponding eigenvalues in opposite signs. When a disordered photonic lattice, an array of evanescently coupled waveguides, is illuminated with an extended coherent optical field, discrete speckle develops. Numerical simulations and analytical modeling reveal that discrete speckle shows a set of surprising features, that are qualitatively indistinguishable in both disorder classes. First, the fingerprint of transverse Anderson localization  associated with disordered lattices, is exhibited in the narrowing of the spatial coherence function. Second, the transverse coherence length (or speckle grain size) freezes upon propagation. Third, the axial coherence depth is independent of the axial position, thereby resulting in a coherence voxel of fixed volume independently of position.When a single lattice site is coherently excited, I discovered that a thermalization gap emerges for light propagating in disordered lattices endowed with disorderimmune chiral symmetry. In these systems, the span of subthermal photon statistics is inaccessible to the input coherent light, which  once the steady state is reached  always emerges with superthermal statistics no matter how small the disorder level. An independent constraint of the input field for the chiral symmetry to be activated and the gap to be observed is formulated. This unique feature enables a new form of photonstatistics interferometry: by exciting two lattice sites with a variable relative phase, as in a traditional twopath interferometer, the excitationsymmetry of the chiral mode pairs is judiciously broken and interferometric control over the photon statistics is exercised, spanning subthermal and superthermal regimes. By considering an ensemble of disorder realizations, this phenomenon is demonstrated experimentally: a deterministic tuning of the intensity fluctuations while the mean intensity remains constant.Finally, I examined the statistics of the emerging light in two different lattice topologies: linear and ring lattices. I showed that the topology dictates the light statistics in the offdiagonal case: for evensited ring and linear lattices, the electromagnetic field evolves into a single quadrature component, so that the field takes discrete phase values and is noncircular in the complex plane. As a consequence, the statistics become superthermal. For oddsited ring lattices, the field becomes random in both quadratures resulting in subthermal statistics. However, this effect is suppressed due to the transverse localization of light in lattices with high disorder. In the diagonal case, the lattice topology does not play a role and the transmitted field always acquires random components in both quadratures, hence the phase distribution is uniform in the steady state.
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Date Issued

2015

Identifier

CFE0005968, ucf:50786

Format

Document (PDF)

PURL

http://purl.flvc.org/ucf/fd/CFE0005968