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Title: On historical materialism.
Creator: Engels, Friedrich
Date Issued: 1940
Identifier: 2100344, CFDT2100344, ucf:4912
Format: Document (PDF)
PURL: http://purl.flvc.org/FCLA/DT/2100344

Title: How the gods were made: A study in historical materialism.
Creator: Keracher,John
Date Issued: 1929
Identifier: 369236, CFDT369236, ucf:5405
Format: Document (PDF)
PURL: http://purl.flvc.org/FCLA/DT/369236

Title: THE GENDERED ALTAR: WICCAN CONCEPTS OF GENDER AND RITUAL OBJECTS.
Creator: Sloan, Jesse, Zorn, Elayne, University of Central Florida
Abstract / Description: Many ethnographic accounts within the annals of anthropological literature describe the religious beliefs and magical rituals of peoples throughout the world. Fewer scholars have focused on the relatively young Neo-Pagan religious movement. "Neo-Pagan," explains Helen Berger in Voices from the Pagan Census (2003), "is an umbrella term covering sects of a new religious movement, the largest and most important form of which is…Wicca" (Berger et al. 2003: 1). This thesis examines the...
Show moreMany ethnographic accounts within the annals of anthropological literature describe the religious beliefs and magical rituals of peoples throughout the world. Fewer scholars have focused on the relatively young Neo-Pagan religious movement. "Neo-Pagan," explains Helen Berger in Voices from the Pagan Census (2003), "is an umbrella term covering sects of a new religious movement, the largest and most important form of which is…Wicca" (Berger et al. 2003: 1). This thesis examines the relationship between practice and ideology by analyzing the material culture of Wiccan altars as used by Wiccans in Central Florida, USA. Particular attention is paid to beliefs concerning concepts of gender associated with ritual objects, and concepts of gender and sexuality as understood by practitioners. Many Wiccans see divinity as manifested in two complementary beings: the Goddess and the God. The fertility that these divine beings achieve through sexual union is the subject of an elaborate ritual called the Great Rite. A pair of Wiccans, often a masculine High Priest and a feminine High Priestess, conduct this ritual by manipulating specific objects, which are believed to be strongly gendered. I argue that Wiccan rituals reflect, construct, and reinforce the Wiccan precept of a gender-balanced cosmos through the interaction of these primary ritual actors and the gendered objects they manipulate. As a practicing Wiccan, my theoretical approach is aligned with that of the native scholar. The native scholar faces challenges distancing her or himself from research, but gains opportunities from insider knowledge. Wiccan ideology stands in contrast to heteronormative conventions of gender and sexuality. However, gay, lesbian, bisexual, and transgender Wiccans may need to actively negotiate for representation in this movement, where fertility is stressed. Wiccans continuously reinvent established practices in an attempt to create a more satisfying religious community.
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Date Issued: 2008
Identifier: CFE0002176, ucf:47525
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002176

Title: Third Order Nonlinearity of Organic Molecules.
Creator: Hu, Honghua, Vanstryland, Eric, Hagan, David, Zeldovich, Boris, Hernandez, Florencio, University of Central Florida
Abstract / Description: The main goal of this dissertation is to investigate the third-order nonlinearity of organic molecules. This topic contains two aspects: two-photon absorption (2PA) and nonlinear refraction (NLR), which are associated with the imaginary and real part of the third-order nonlinearity (?(3)) of the material, respectively. With the optical properties tailored through meticulous molecular structure engineering, organic molecules are promising candidates to exhibit large third-order nonlinearities....
Show moreThe main goal of this dissertation is to investigate the third-order nonlinearity of organic molecules. This topic contains two aspects: two-photon absorption (2PA) and nonlinear refraction (NLR), which are associated with the imaginary and real part of the third-order nonlinearity (?(3)) of the material, respectively. With the optical properties tailored through meticulous molecular structure engineering, organic molecules are promising candidates to exhibit large third-order nonlinearities. Both linear (absorption, fluorescence, fluorescence excitation anisotropy) and nonlinear (Z-scan, two-photon fluorescence, pump-probe) techniques are described and utilized to fully characterize the spectroscopic properties of organic molecules in solution or solid-state form. These properties are then analyzed by quantum chemical calculations or other specific quantum mechanical model to understand the origins of the nonlinearities as well as the correlations with their unique molecular structural features. These calculations are performed by collaborators. The 2PA study of organic materials is focused on the structure-2PA property relationships of four groups of dyes with specific molecular design approaches as the following: (1) Acceptor-?-Acceptor dyes for large 2PA cross section, (2) Donor-?-Acceptor dyes for strong solvatochromic effects upon the 2PA spectra, (3) Near-infrared polymethine dyes for a symmetry breaking effect, (4) Sulfur-squaraines vs. oxygen-squaraines to study the role of sulfur atom replacement upon their 2PA spectra. Additionally, the 2PA spectrum of a solid-state single crystal made from a Donor-?-Acceptor dye is measured, and the anisotropic nonlinearity is studied with respect to different incident polarizations. These studies further advance our understanding towards an ultimate goal to a predictive capability for the 2PA properties of organic molecules. The NLR study on molecules is focused on the temporal and spectral dispersion of the nonlinear refraction index, n2, of the molecules. Complicated physical mechanisms, originating from either electronic transitions or nuclei movement, are introduced in general. By adopting a prism compressor / stretcher to control the pulsewidth, an evolution of n2 with respect to incident pulsewidth is measured on a simple inorganic molecule (-)carbon disulfide (CS2) in neat liquid at 700 nm and 1064 nm to demonstrate the pulsewidth dependent nonlinear refraction. The n2 spectra of CS2 and certain organic molecules are measured by femtosecond pulses, which are then analyzed by a 3-level model, a simplified (")Sum-over-states(") quantum mechanical model. These studies can serve as a precursor for future NLR investigations.
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Date Issued: 2012
Identifier: CFE0004387, ucf:49400
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004387

Title: Nanoarchitectured Energy Storage Devices.
Creator: Yu, Zenan, Thomas, Jayan, Seal, Sudipta, Zhai, Lei, Fang, Jiyu, Sundaram, Kalpathy, University of Central Florida
Abstract / Description: Supercapacitors, the devices that connect the gap between batteries and conventional capacitors, have recently attracted significant attention due to their high specific capacitance, substantially enhanced power and energy densities, and extraordinary cycle life. In order to realize even better performance with supercapacitors, rejuvenated effort towards developing nanostructured electrodes is necessary. In this dissertation, several strategic directions of nanoarchitecturing the electrodes...
Show moreSupercapacitors, the devices that connect the gap between batteries and conventional capacitors, have recently attracted significant attention due to their high specific capacitance, substantially enhanced power and energy densities, and extraordinary cycle life. In order to realize even better performance with supercapacitors, rejuvenated effort towards developing nanostructured electrodes is necessary. In this dissertation, several strategic directions of nanoarchitecturing the electrodes to enhance the performance of supercapacitors are investigated. An introduction and background of supercapacitors, which includes motivation, classification and working principles, recent nanostructured electrode materials studies, and devices fabrication, are initially presented. A facile method, called Spin-on Nanoprinting (SNAP), to fabricate highly ordered manganese dioxide (MnO2) nanopillars is introduced. The SNAP method that is further modified to develop carbon nanoarray electrodes is also discussed. Subsequently, a template-free method to develop high aspect ratio copper oxide nanowhiskers on copper substrate is presented, which boosts the surface area by 1000 times compared to non-nanostructured copper substrate. Electrochemically deposited MnO2 on the nanostructured substrate provided a specific capacitance of about 1379 F g-1 which is very close to the theoretical value (~ 1400 F g-1) due to this efficient nanostructure design. In addition, a novel method to decorate metal nanoparticles on graphene aerogel, which considerably enhances the electronic conductivity and the corresponding specific capacitance, is demonstrated. Moreover, ferric oxide (Fe2O3) nanorods prepared by a simple hydrothermal method is discussed. Asymmetric devices assembled based on Fe2O3 nanorods and MnO2 nanowhiskers show excellent electrochemical properties. The devices not only display the capability to store energy but also transmit electricity through the inner copper core. These two functions are independent and do not interfere with each other. Finally, a summary of this dissertation as well as some potential future directions are presented.
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Date Issued: 2015
Identifier: CFE0006062, ucf:50995
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006062

Title: High Temperature Materials Characterization and Sensor Application.
Creator: Ren, Xinhua, Gong, Xun, Wahid, Parveen, Wu, Xinzhang, An, Linan, University of Central Florida
Abstract / Description: This dissertation presents new solutions for turbine engines in need of wireless temperature sensors at temperatures up to 1300oC. Two important goals have been achieved in this dissertation. First, a novel method for precisely characterizing the dielectric properties of high temperature ceramic materials at high temperatures is presented for microwave frequencies. This technique is based on a high-quality (Q)-factor dielectrically-loaded cavity resonator, which allows for accurate...
Show moreThis dissertation presents new solutions for turbine engines in need of wireless temperature sensors at temperatures up to 1300oC. Two important goals have been achieved in this dissertation. First, a novel method for precisely characterizing the dielectric properties of high temperature ceramic materials at high temperatures is presented for microwave frequencies. This technique is based on a high-quality (Q)-factor dielectrically-loaded cavity resonator, which allows for accurate characterization of both dielectric constant and loss tangent of the material. The dielectric properties of Silicon Carbonitride (SiCN) and Silicoboron Carbonitride (SiBCN) ceramics, developed at UCF Advanced Materials Processing and Analysis Center (AMPC) are characterized from 25 to 1300oC. It is observed that the dielectric constant and loss tangent of SiCN and SiBCN materials increase monotonously with temperature. This temperature dependency provides the valuable basis for development of wireless passive temperature sensors for high-temperature applications. Second, wireless temperature sensors are designed based on the aforementioned high-temperature ceramic materials. The dielectric constant of high-temperature ceramics increases monotonically with temperature and as a result changes the resonant frequency of the resonator. Therefore, the temperature can be extracted by measuring the change of the resonant frequency of the resonator. In order for the resonator to operate wirelessly, antennas need to be included in the design. Three different types of sensors, corresponding to different antenna configurations, are designed and the prototypes are fabricated and tested. All of the sensors successfully perform at temperatures over 1000oC. These wireless passive sensor designs will significantly benefit turbine engines in need of sensors operating at harsh environments.
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Date Issued: 2012
Identifier: CFE0004791, ucf:49727
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004791

Title: Dialectical and historical materialism.
Creator: Stalin, Joseph
Date Issued: 1940
Identifier: 2660283, CFDT2660283, ucf:4984
Format: Document (PDF)
PURL: http://purl.flvc.org/FCLA/DT/2660283

Title: Catalytic Properties of Defect-Laden 2D Material from First-Principles.
Creator: Jiang, Tao, Rahman, Talat, Stolbov, Sergey, Blair, Richard, Tetard, Laurene, University of Central Florida
Abstract / Description: Two dimensional (2D) materials offer excellent opportunities for application as catalysts for energy needs. Their catalytic activity depends on the nature of defects, their geometry and their electronic structure. It thus important that the characteristics of defect-laden 2D materials be understood at the microscopic level. My dissertation focuses on theoretical and computational studies of several novel nanoscale materials using state-of-the-art techniques based on density functional theory ...
Show moreTwo dimensional (2D) materials offer excellent opportunities for application as catalysts for energy needs. Their catalytic activity depends on the nature of defects, their geometry and their electronic structure. It thus important that the characteristics of defect-laden 2D materials be understood at the microscopic level. My dissertation focuses on theoretical and computational studies of several novel nanoscale materials using state-of-the-art techniques based on density functional theory (DFT) with the objective of understanding the microscopic factors that control material functionality.My work has helped establish defect-laden hexagonal boron nitride (dh-BN) as a promising metal-free catalyst for CO2 hydrogenation. Firstly, I showed how small molecules (H2, CO, CO2) interacting with several kinds of defects in dh-BN (with nitrogen or boron vacancy, boron substituted for nitrogen, Stone-Wales defect). I analyzed binding energies and electronic structures of adsorption of molecules on dh-BN to predict their catalytic activities. Then by computational efforts on reaction pathways and activation energy barriers, I found that vacancies induced in dh-BN can effectively activate the CO2 molecule for hydrogenation, where activation occurs through back-donation to the ?* orbitals of CO2 from frontier orbitals (defect state) of the h-BN sheet localized near a nitrogen vacancy (VN). Subsequent hydrogenation to formic acid (HCOOH) and methanol (CH3OH), indicating dh-BN (VN) an excellent metal-free catalyst for CO2 reduction, which may serve as a solution for global energy and sustainability.At the same time, I studied critical steps of the catalytic processes from carbon monoxide and methanol to higher alcohol on single-layer MoS2 functionalized with small Au nanoparticle, indicating C-C coupling feasible on MoS2-Au13, which led to production of acetaldehyde (CH3CHO). Whereas a bilayer 31-atom cluster of gold on MoS2 show excellent catalytic performance on CO hydrogenation to methanol through two effective pathways
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Date Issued: 2019
Identifier: CFE0007823, ucf:52822
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007823

Title: SMART MATERIAL ACTUATION AND MORPHING FOR UNMANNED AIRCRAFT SYSTEMS.
Creator: Da Silva Lima, Caio H, Kauffman, Jeffrey L., University of Central Florida
Abstract / Description: The intent of this thesis is to outline the design, analysis, and characterization of an axially compressed piezocomposite actuator and, in particular, to determine the correlation and accuracy of two models used to predict deflection of an axially compressed piezocomposite bimorph. Restrictions in material properties lead to vehicle inefficiencies caused by the discontinuous geometry of deflected control surfaces in unmanned aircraft systems. This performance disadvantage in discrete control...
Show moreThe intent of this thesis is to outline the design, analysis, and characterization of an axially compressed piezocomposite actuator and, in particular, to determine the correlation and accuracy of two models used to predict deflection of an axially compressed piezocomposite bimorph. Restrictions in material properties lead to vehicle inefficiencies caused by the discontinuous geometry of deflected control surfaces in unmanned aircraft systems. This performance disadvantage in discrete control surfaces is caused in part by the sharp edges that are formed when the surface is pivoted. Flow continuity over the body of a vehicle is important in minimizing the effects of drag and, in turn, increasing aerodynamic performance. An efficient alternative to discrete control surface actuation is axially compressed piezocomposite actuation which could potentially improve the efficiency of the vehicle in all environments. Bimorph performance in angular deflection and displacement for the PA16N and MFC-M8528-P1 piezocomposites is analyzed using a Classical Laminate Plate Theory (CLPT) model and an Elastica model. Model accuracy is verified through experimental testing of a PA16N bimorph. CLPT model is shown to be accurate to within .05 mm and Elastica model is shown to be accurate to within .04 mm for axial forces below 30 N. Correlation between the mathematical models is confirmed. Experimental results for the PA16N show that a 30 N compression force applied to the bimorph can increase the maximum displacement by approximately 2.5 times the original displacement.
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Date Issued: 2016
Identifier: CFH2000095, ucf:45563
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000095

Title: MECHANICAL CHARACTERIZATION OF ANISOTROPIC FUSED DEPOSITION MODELED POLYLACTIC ACID UNDER COMBINED MONOTONIC BENDING AND TORSION CONDITIONS.
Creator: Santomauro, Aaron T, Gordon, Ali P., University of Central Florida
Abstract / Description: Mechanical strength of polylactic acid (PLA) is increasingly relevant with time because of its attractive mechanical properties and 3D printability. Additive manufacturing (AM) methods, such as fused deposition modeling (FDM), stereolithography (SLA), and selective laser sintering (SLS), serve a vital role in assisting designers with cheap and efficient generation of the desired components. This document presents research to investigate the anisotropic response of multi-oriented PLA subjected...
Show moreMechanical strength of polylactic acid (PLA) is increasingly relevant with time because of its attractive mechanical properties and 3D printability. Additive manufacturing (AM) methods, such as fused deposition modeling (FDM), stereolithography (SLA), and selective laser sintering (SLS), serve a vital role in assisting designers with cheap and efficient generation of the desired components. This document presents research to investigate the anisotropic response of multi-oriented PLA subjected to multiple monotonic loading conditions. Although empirical data has previously been captured for multi-oriented PLA under tensile and compressive loading conditions, the data has yet to be applied with regard to a representative component geometry. The tensile and compressive empirical data were ultimately used to develop elastic and yield constitutive models which aided in the characterization of PLA under torsion and bending. This representative component geometry is expected to experience a combined torsion and bending load condition in an effort to address this integral gap in the mechanical properties of multi-oriented PLA. In addition to the acquired empirical data, finite element analysis (FEA) and analytical modeling are employed to supplement the accurate modeling of future component analysis. As a result of the proposed array of experiments, the torsional and bending capabilities of PLA are forecasted to vary based on the print orientation. Lastly, the broader impact of this work is dedicated to addressing the material's capability to operate in environments which possess significant torsion and bending such as model aircraft wings and shafts for remote controlled cars.
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Date Issued: 2019
Identifier: CFH2000550, ucf:45631
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000550

Title: QUANTITATIVE THICKNESS MAPPING IN HIGH-ANGLE ANNULAR DARK-FIELD (HAADF) SCANNING TRANSMISSION ELECTRON MICROSCOPY (STEM).
Creator: Nukala, Haritha, Heinrich, Helge, University of Central Florida
Abstract / Description: Only a few methods are currently available for the measurement of sample thicknesses in Transmission Electron Microscopy (TEM). These methods, Convergent-Beam Electron Diffraction (CBED) and thickness mapping in Energy-Filtered TEM (EFTEM), are either elaborate or complex. In this present work, I have investigated and come up with a simple straight-forward method to measure the local thickness of a TEM sample with the atomic number (Z-contrast) imaging using High-Angle Annular Dark Field ...
Show moreOnly a few methods are currently available for the measurement of sample thicknesses in Transmission Electron Microscopy (TEM). These methods, Convergent-Beam Electron Diffraction (CBED) and thickness mapping in Energy-Filtered TEM (EFTEM), are either elaborate or complex. In this present work, I have investigated and come up with a simple straight-forward method to measure the local thickness of a TEM sample with the atomic number (Z-contrast) imaging using High-Angle Annular Dark Field (HAADF) Scanning Transmission Electron Microscopy (STEM). HAADF STEM shows atomic number contrast for high scattering angles of the electrons, owing to predominant electron scattering at the potential of the nucleus similar to Rutherford scattering. The characterization of materials by STEM helps to identify microstructures and nanostructures within a sample and to analyze defects in samples. HAADF STEM imaging is capable of resolving atomic structures with better than 2 Å lateral resolution. However, HAADF STEM has so far not been systematically used to measure sample thicknesses. In Z-contrast imaging, it was known that the intensity of the electrons scattered to high angles increases with increase in the atomic number (Z) of the element/compound with increasing thickness of the sample based on the equation, I ~ t.Zα Where t, is the thickness and α, is a parameter between 1 and 2. This project was started with this simple approach, but the experimental results within the thesis show that the relation between the intensity and the atomic number is not well described by this equation. A more reliable parameter, σZ, the interaction coefficient of the material was calculated. Samples containing Ag2Al platelets in Al matrix were used for calibration purposes. Additional samples containing layers of known elements/compounds were obtained from TriQuint Semiconductors and from the Physics department of UCF to calculate σ for various elements/compounds. These experimental values were used to measure the local thicknesses in nanoparticles and also the total volume of the nanoparticles. This quantitative HAADF STEM analysis represents a new method, which can be added to the list of methods used for the purpose of measurement of the local thickness of a sample in the TEM. This method is especially useful for the thickness measurement of nanoparticles. The other two methods, CBED and thickness maps in EFTEM are strongly affected by the sample orientation and therefore not appropriate for the study of nanoparticle thicknesses, whereas orientation effects are negligible for the conditions used in this HAADF STEM analysis.
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Date Issued: 2008
Identifier: CFE0002309, ucf:47859
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002309

Title: ENCAPSULATED NANOSTRUCTURED PHASE CHANGE MATERIALS FOR THERMAL MANAGEMENT.
Creator: Hong, Yan, Su, Ming, University of Central Florida
Abstract / Description: A major challenge of developing faster and smaller microelectronic devices is that high flux of heat needs to be removed efficiently to prevent overheating of devices. The conventional way of heat removal using liquid reaches a limit due to low thermal conductivity and limited heat capacity of fluids. Adding solid nanoparticles into fluids has been proposed as a way to enhance thermal conductivity of fluids, but recent results show inconclusive anomalous enhancements in thermal conductivity....
Show moreA major challenge of developing faster and smaller microelectronic devices is that high flux of heat needs to be removed efficiently to prevent overheating of devices. The conventional way of heat removal using liquid reaches a limit due to low thermal conductivity and limited heat capacity of fluids. Adding solid nanoparticles into fluids has been proposed as a way to enhance thermal conductivity of fluids, but recent results show inconclusive anomalous enhancements in thermal conductivity. A possible way to improve heat transfer is to increase the heat capacity of liquid by adding phase change nanoparticles with large latent heat of fusion into the liquid. Such nanoparticles absorb heat during solid to liquid phase change. However, the colloidal suspension of bare phase change nanoparticles has limited use due to aggregation of molten nanoparticles, irreversible sticking on fluid channels, and dielectric property loss. This dissertation describes a new method to enhance the heat transfer property of a liquid by adding encapsulated phase change nanoparticles (nano-PCMs), which will absorb thermal energy during solid-liquid phase change and release heat during freeze. Specifically, silica encapsulated indium nanoparticles, and polymer encapsulated paraffin (wax) nanoparticles have been prepared using colloidal method, and dispersed into poly-±-olefin (PAO) and water for high temperature and low temperature applications, respectively. The shell, with a higher melting point than the core, can prevent leakage or agglomeration of molten cores, and preserve the dielectric properties of the base fluids. Compared to single phase fluids, heat transfer of nanoparticle-containing fluids have been significantly enhanced due to enhanced heat capacities. The structural integrity of encapsulation allows repeated uses of nanoparticles for many cycles. By forming porous semi crystalline silica shells obtained from water glass, supercooling has been greatly reduced due to low energy barrier of heterogeneous nucleation. Encapsulated phase change nanoparticles have also been added into exothermic reaction systems such as catalytic and polymerization reactions to effectively quench local hot spots, prevent thermal runaway, and change product distribution. Specifically, silica-encapsulated indium nanoparticles, and silica encapsulated paraffin (wax) nanoparticles have been used to absorb heat released in catalytic reaction, and to mitigate the gel effect during polymerization, respectively. The reaction rates do not raise significantly owing to thermal buffering using phase change nanoparticles at initial stage of thermal runaway. The effect of thermal buffering depends on latent heats of fusion of nanoparticles, and heat releasing kinetics of catalytic reactions and polymerizations. Micro/nanoparticles of phase change materials will open a new dimension for thermal management of exothermic reactions.
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Date Issued: 2011
Identifier: CFE0003698, ucf:48816
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003698

Title: A Comparison of Corrosion Rates Determined by Polarizations Resistance Measurements for Zinc and Cadmium Metal Immersed in NonStirred Aqueous Portland Cement Solution.
Creator: Moore, William J., Baldwin, Vaniah, Jr., Engineering
Abstract / Description: Florida Technological University College of Engineering Thesis; The effect of nonstirred aqueous portland cement solution on the corrosion rates of zinc and cadmium metal using Tafel extropolation and linear polarization measurements has been investigated. Results indicate that for the corrosion systems under investigation, zinc metal has a higher corrosion potential and lower corrosion rate than cadmium metal.
Date Issued: 1975
Identifier: CFR0008129, ucf:52969
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFR0008129

Title: Characterization of Waste-To-Energy (WTE) Bottom and Fly Ashes in Cementitious Materials.
Creator: An, Jin Woo, Nam, Boo Hyun, Yun, Hae-Bum, Chopra, Manoj, An, Linan, University of Central Florida
Abstract / Description: Waste-to-Energy (WTE) ashes (or called as municipal solid waste incineration ashes) have been recycled in the areas of road bed, asphalt paving, and concrete products in many European and Asian countries. In those countries, recycling programs (including required physical properties and environmental criteria) of ash residue management have been developed so as to encourage and enforce the reuse for WTE ashes instead of landfill disposal. However, the U.S. has shown a lack of consistent and...
Show moreWaste-to-Energy (WTE) ashes (or called as municipal solid waste incineration ashes) have been recycled in the areas of road bed, asphalt paving, and concrete products in many European and Asian countries. In those countries, recycling programs (including required physical properties and environmental criteria) of ash residue management have been developed so as to encourage and enforce the reuse for WTE ashes instead of landfill disposal. However, the U.S. has shown a lack of consistent and effective management plans as well as environmental regulations for the use of WTE ashes. Many previous studies demonstrated the potential beneficial use of WTE ash as an engineering material with minimum environmental impacts. Due to persistent uncertainty of engineering properties and inconsistency in the Federal and State regulations in the U.S., the recycling of WTE ash has been hindered, and they are mostly disposed of in landfills. The goal of this study is to identify beneficial use of WTE ashes as construction materials; thus, the recycling program of WTE ashes will become more active in the U.S. One of potential applications for the WTE ashes can be cement-based materials because the ashes contain good chemical components such as calcium and silicon. Moreover, toxics (heavy metals) can be bound or encapsulated in cement matrix; thus, the leaching potential can be reduced. The specific objectives are: (1) to understand the current practice of the reuse of WTE ashes as construction materials, (2) to physically and chemically characterize WTE bottom and fly ashes, (3) to investigate the effects of WTE bottom and fly ashes in cementitious materials (e.g. cement paste and concrete) as replacement of either cement of fine aggregate with emphasis on cement hydration, and (4) to investigate the environmental impacts of WTE bottom ash on leaching when used in cement-based materials. Fundamental properties of MSWI bottom ash and fly ash were studied by conducting physical, microstructural, and chemical tests. Petrographic examinations, such as scanning electron microscopy (SEM), energy dispersive x-ray (EDX), and x-ray diffraction (XRD) were performed in order to identify chemical composition of the ash and to determine their contents. To evaluate the main side effect of ash when used in concrete, the creation of a network of bubbles due to the presence of aluminum, ashes and aluminum powder were submerged in high pH solution, and the evolution of hydrogen gas was measured. Efforts were made to investigate the influence of WTE ashes on engineering properties of cement paste and concrete specimens when part of Portland cement and fine aggregate are replaced with ground and sieved WTE ashes. Cement paste and concrete cylinders were cast with various amounts of mineral and fine aggregate additions, respectively, and their strength and durability were investigated. Subsequently, optimum mix proportioning of the WTE ashes was investigated when they are used in cement paste and concrete specimens. In addition, the leaching characteristics of major alkaline and trace elements from concrete containing varied amounts (10%-50%) of BA were investigated by Synthetic Precipitation Leaching Procedure (SPLP) batch testing.
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Date Issued: 2015
Identifier: CFE0006251, ucf:51070
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006251

Title: Power Effects on Consumer Well-Being: Two Essays on The Power Effects on Donation and Material/Experiential Consumption.
Creator: Liu, Yue, He, Xin, Tafaghodijami, Ata, Massiah, Carolyn, Yang, Xiaojing, Mao, Huifang, University of Central Florida
Abstract / Description: Power is a fundamental concept in social science (Russell 1938), which has gained much academic attention in various disciplines. Two essays of this dissertation examine the theoretical and practical implications of power effects on donation decisions and material/experiential consumption.The first essay demonstrates power's moderating effect on the relationship between publicity and donation. Specifically, it is proposed that powerful people tend to donate more in public (vs. private)...
Show morePower is a fundamental concept in social science (Russell 1938), which has gained much academic attention in various disciplines. Two essays of this dissertation examine the theoretical and practical implications of power effects on donation decisions and material/experiential consumption.The first essay demonstrates power's moderating effect on the relationship between publicity and donation. Specifically, it is proposed that powerful people tend to donate more in public (vs. private) situation, whereas powerless people do not show such a difference. This effect is driven by people's concern about self-presentation in a donation scenario. Additionally, this effect only holds when people strongly believe that high donation enhances others' positive impression of them, but dilutes when such belief is not held. The theorizing is supported across four studies.The second essay focuses on how power influences consumers' preferences for material and experiential products. It is predicted that those who feel powerless tend to spend more of their discretionary money on material products than experiential products. This effect occurs through feelings of resourcefulness caused by possessing material or experiential goods. In addition, this effect is further moderated by implicit theory, such that the impact of power on material versus experience product choice persists for incremental theorists but dissipates for entity theorists. Three experiments provide support to this proposition.Overall, by investigating how power influences people's donation behavior and choice of material/experiential products, this dissertation strengthens the understanding of power's effectson consumer behavior and provides practical implications on how power status can influence consumers' well-being.
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Date Issued: 2017
Identifier: CFE0006894, ucf:51710
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006894

Title: Carbon nanotube (CNT) metallic composite with focus on processing and the resultant properties.
Creator: Billah, Md Muktadir, Chen, Quanfang, Bai, Yuanli, An, Linan, Orlovskaya, Nina, University of Central Florida
Abstract / Description: Metal-carbon nanotubes (CNTs) composites are the promising advanced materials that are being developed to take the advantage of the exceptional properties of CNTs. Because of the intrinsically strong in-plane atomic SP2 bonding CNTs offer high young's modulus (1.0(-)1.8 TPa), high tensile strength (30(-)200 GPa) and high elongation at break (10(-)30%). The thermal conductivity of individual single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) are about 6000 W/m-K and...
Show moreMetal-carbon nanotubes (CNTs) composites are the promising advanced materials that are being developed to take the advantage of the exceptional properties of CNTs. Because of the intrinsically strong in-plane atomic SP2 bonding CNTs offer high young's modulus (1.0(-)1.8 TPa), high tensile strength (30(-)200 GPa) and high elongation at break (10(-)30%). The thermal conductivity of individual single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) are about 6000 W/m-K and 3000 W/m-K, respectively. Therefore it is expected that by incorporation of CNTs in metal matrices multi-functional composites can be used ideally as thermal interface materials, light-weight high-strength structural materials, electric components, optical devices, electromagnetic absorption materials etc. However, so far results are far from satisfied for CNT composites, mainly due to the fact that there are two main key issues remained without good solutions for CNT composites: the poor uniformity in CNT dispersion and the weak interfacial bonding between CNTs and the matrices. In this study, MWCNTs were functionalized and coated with metals like Cu and Ni by electroless deposition methods prior to their application. Metal coatings result in strong interfacial bonding at CNT-metal interfaces and uniform dispersion. During metal coating processes CNTs are physically separated in electrolyte and after coating they get physically retain the separation by the coated metal layer that they are not allowed to aggregate to form bundles. Moreover, after metal coating, the resultant density of Ni-coated MWCNTs is close to that of molten metal matrix. This prevent separation of CNTs due to buoyancy effects and results in uniform dispersion. Metal coating on CNTs surfaces also allows to form strong interfacial bonding with the metal matrices.SnBi alloy has been identified as novel lead-free thermal interface material (TIM) for electronics packaging. However the thermal conductivity and the mechanical strength of pure SnBi alloy are not sufficient to withstand harsh environment imposed by powder electronics. Therefor how to increase the thermal conductivity and the mechanical strength of SnBi solders becomes important. In this study, MWCNTs have been added into SnBi alloy to form SnBi/CNT composite solders by different material processing methods. First, in sandwich method Cu-coated CNTs were added to the 70Sn-30Bi alloy and mixed mechanically. UTS was increased by 47.6% for 3 wt. % Cu/CNTs addition. Second. Ni-coated CNTs were added by sonication assisted melting method in fabricating 70Sn-30Bi solder. For 3 wt. % Ni-coated MWCNTs, equivalent to 0.6 wt. % pure MWCNTs, UTS and YS were increased by 88.8 % and 112.3% respectively. In addition the thermal conductivity was also increased by more than 70%. Ni-coated CNTs were also added to pure Al by powder metallurgy method. For 7 wt. % Ni/CNTs having diameter 30-50 nm, UTS and YS were increased by 92.7% and 101.6% respectively. For CNTs having diameter 8-15 nm, UTS and YS were increased by 108.9% and 128.2% respectively for 7 wt. % addition. All these results are first time obtained that are much greater than published data on CNT/metal composites. Results discussion and mechanism in reinforcement were also presented.
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Date Issued: 2017
Identifier: CFE0006567, ucf:51320
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006567

Title: The effect of electron-hole 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 electron-hole pairs in materials has great importance. In directbandgap semiconductor materials, the mechanism of radiative recombination of electron-holepairs leads to the emission of photons, which is the basis of Light Emitting Diodes(LEDs). The excitation of electron-hole 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 electron-hole pairs in materials has great importance. In directbandgap semiconductor materials, the mechanism of radiative recombination of electron-holepairs leads to the emission of photons, which is the basis of Light Emitting Diodes(LEDs). The excitation of electron-hole 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,electron-hole pairs excitation is a key for the device performance. Diodes and transistorsare also great discoveries in electronics which rely on the generation and recombination ofelectron-hole pairs at p-n junctions. In three-dimensional topological insulators (3D TIs)materials nanostructures excitation of electron-hole pairs can be utilized for the quantummemory, quantum information and quantum teleportation. In two-dimensional (2D) layeredmaterials like graphene, MoS_2, MoSe_2, WS_2 and WSe_2 generation and recombination ofelectron hole pairs is main process at p-n junctions, infrared detectors and sensors.This PhD thesis is concerned with the physics of different types of electron-hole pairsin various materials, such as wide-bandgap 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 metal-dielectric 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 electron-hole 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 core-bulk heterostructure. When a 3D TI QD is embedded inside a cavity, the single-photon 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 electron-hole 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 single-layer 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: Investigation of different dielectric materials as gate insulator for MOSFETs.
Creator: Oswal, Ritika, Sundaram, Kalpathy, Kapoor, Vikram, Wahid, Parveen, University of Central Florida
Abstract / Description: The scaling of semiconductor transistors has led to a decrease in thickness of the silicon dioxide layer used as gate dielectric. The thickness of the silicon dioxide layer is reduced to increase the gate capacitance, thus increasing the drain current. If the thickness of the gate dielectric decreases below 2nm, the leakage current due to the tunneling increases drastically. Hence it is necessary to replace the gate dielectric, silicon dioxide, with a physically thicker oxide layer of high-k...
Show moreThe scaling of semiconductor transistors has led to a decrease in thickness of the silicon dioxide layer used as gate dielectric. The thickness of the silicon dioxide layer is reduced to increase the gate capacitance, thus increasing the drain current. If the thickness of the gate dielectric decreases below 2nm, the leakage current due to the tunneling increases drastically. Hence it is necessary to replace the gate dielectric, silicon dioxide, with a physically thicker oxide layer of high-k materials like Hafnium oxide and Titanium oxide. High-k dielectric materials allow the capacitance to increase without a huge leakage current. Hafnium oxide and Titanium oxide films are deposited by reactive magnetron sputtering from Hafnium and Titanium targets respectively. These oxide layers are used to create metal-insulator-metal (MIM) structures using aluminum as the top and bottom electrodes. The films are deposited at various O2/Ar gas flow ratios, substrate temperatures, and process pressures. After attaining an exact recipe for these oxide layers that exhibit the desired parameters, MOS capacitors are fabricated with n-Si and p-Si substrates having aluminum electrodes at the top and bottom of each. Comparing the parameters of Hafnium oxide- and Titanium oxide- based MOS capacitors, MOSFET devices are designed with Hafnium oxide as gate dielectric.
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Date Issued: 2014
Identifier: CFE0005226, ucf:50612
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005226

Title: METHOD TO DISCRETIZE CONTINUOUS GRADIENT STRUCTURES AND CALCULATE THERMAL RESIDUAL STRESSES WITHIN LAYERED FUNCTIONALLY GRADED CERAMICS.
Creator: Neale, Ryan E, Orlovskaya, Nina, University of Central Florida
Abstract / Description: Functionally graded materials (FGMs) are an advanced class of material which seeks to leverage the strengths of one material to mitigate the weaknesses of another. This allows for operation in extreme environments or conditions where materials properties must change at various locations within a structure. Fabrication of this advanced class of material is limited due to geometric, economic, and material constraints inherent in the various methods. For this reason, a model was developed to...
Show moreFunctionally graded materials (FGMs) are an advanced class of material which seeks to leverage the strengths of one material to mitigate the weaknesses of another. This allows for operation in extreme environments or conditions where materials properties must change at various locations within a structure. Fabrication of this advanced class of material is limited due to geometric, economic, and material constraints inherent in the various methods. For this reason, a model was developed to discretize continuous gradient curves to allow for the use of a step-wise approximations to such gradients. These alternative step-wise gradients would allow for the use of numerous manufacturing techniques which have improved composition control, cost of processing, cost of equipment, and equipment availability. One such technique, tape casting, was explored due to its robustness and ability to create layered ceramics. Since ceramics are inherently brittle materials, they serve to be strengthened by the thermal residual stresses that form in the creation of these step-wise graded composites. With models to calculate these residual stresses and determine step-wise approximations of various compositional gradients, the process of designing these layered ceramics can be significantly improved.
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Date Issued: 2019
Identifier: CFH2000530, ucf:45633
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000530

Title: EXPERIMENTAL TECHNIQUES FOR NONLINEAR MATERIAL CHARACTERIZATION: A NONLINEAR SPECTROMETER USING A WHITE-LIGHT CONTINUUM Z-SCAN.
Creator: Balu, Mihaela, Van Stryland, Eric, University of Central Florida
Abstract / Description: The main goal of this dissertation is to introduce and demonstrate a new method for the rapid determination of the nonlinear absorption spectra and the dispersion of the nonlinear refraction of optical materials in the visible and near IR spectral regions. However, conventional methods like, white-light continuum pump-probe and Z-scan techniques were used to measure the peak 2PA cross-sections for a number of commercially available photoinitiators. In the new method mentioned above, a high...
Show moreThe main goal of this dissertation is to introduce and demonstrate a new method for the rapid determination of the nonlinear absorption spectra and the dispersion of the nonlinear refraction of optical materials in the visible and near IR spectral regions. However, conventional methods like, white-light continuum pump-probe and Z-scan techniques were used to measure the peak 2PA cross-sections for a number of commercially available photoinitiators. In the new method mentioned above, a high energy, broadband femtosecond white-light continuum is used to replace the single wavelength source conventionally used in a Z-scan experiment. In a Z-scan experiment, the transmittance of a focused beam through a sample is monitored as the sample travels through the focus, in the Z direction, along the focused beam. Providing the sample exhibits nonlinear absorption and/or refraction, the detector monitors a change in transmittance and/or a change in the beam divergence (if the energy is partially collected through an aperture in front of the detector). Replacing the single wavelength source with a white-light continuum allows for a much faster way of measuring nonlinear absorption/refraction spectra. This could eliminate the need for using other tunable sources (e.g. Optical Parameter Generators/Amplifiers) for nonlinear measurements. These sources made nonlinear spectroscopy using Z-scan experiments a time consuming task. This new source/method allows for rapid and simultaneous measurement of the nonlinear absorption spectrum and the dispersion of the nonlinear refraction. We have confirmed the functionality of the continuum as a source for nonlinear optical characterization of materials by using it to perform Z-scans on the well characterized semiconductors ZnSe and ZnS and on solutions of organic dyes.
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Date Issued: 2006
Identifier: CFE0001241, ucf:46934
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001241

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