Current Search: Electric (x)
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Title
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HIGH-DENSITY AND HIGH-EFFICIENCY SOFT SWITCHING MODULAR BI-DIRECTIONAL DC-DC CONVERTER FOR HYBRID ELECTRIC VEHICLES.
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Creator
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Elmes, John, Batarseh, Issa, University of Central Florida
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Abstract / Description
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This dissertation presents the design of a high-density and high-efficiency soft-switching bi-directional DC-DC converter for hybrid-electric vehicles. The converter operates in a new bi-directional interleaved variable-frequency quasi-square-wave (QSW) mode, which enables high efficiency, high switching frequency, and high power-density. The converter presented utilizes a new variable frequency interleaving approach which allows for each module to operate in an interleaved position while...
Show moreThis dissertation presents the design of a high-density and high-efficiency soft-switching bi-directional DC-DC converter for hybrid-electric vehicles. The converter operates in a new bi-directional interleaved variable-frequency quasi-square-wave (QSW) mode, which enables high efficiency, high switching frequency, and high power-density. The converter presented utilizes a new variable frequency interleaving approach which allows for each module to operate in an interleaved position while allowing for tolerance in inductance and snubber capacitor values. The variable frequency interleaved soft-switching operation paired with a high-density nanocrystalline inductor and high-density system structure results in a very high performance converter, well exceeding that of the current technology. The developed converter is intended to achieve three specific performance goals: high conversion efficiency, high power density, and operation with 100 ÃÂÃÂÃÂðC coolant. Two markedly different converter prototype designs are presented, one converter using evaporative spray cooling to cool the switching devices, with the second converter using a more traditional coldplate design to cool the switching devices. The 200 kW (25 kW per module) prototype converters exhibited power density greater than 8 kilowatts/liter (kW/L), and peak efficiency over 98%, while operating with 100 ÃÂÃÂÃÂðC coolant.
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Date Issued
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2010
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Identifier
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CFE0003366, ucf:48436
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0003366
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Title
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A Macro-Level Sustainability Assessment Framework for Optimal Distribution of Alternative Passenger Vehicles.
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Creator
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Onat, Nuri, Tatari, Omer, Nam, Boo Hyun, Oloufa, Amr, Pazour, Jennifer, University of Central Florida
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Abstract / Description
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Although there are many studies focusing on the environmental impacts of alternative vehicle options, social and economic dimensions and trade-off relationships among all of these impacts were not investigated sufficiently. Moreover, most economic analyses are limited to life cycle cost analyses and do not consider macro-level economic impacts. Therefore, this thesis aims to advance the Life Cycle Sustainability Assessment literature and electric vehicle sustainability research by presenting...
Show moreAlthough there are many studies focusing on the environmental impacts of alternative vehicle options, social and economic dimensions and trade-off relationships among all of these impacts were not investigated sufficiently. Moreover, most economic analyses are limited to life cycle cost analyses and do not consider macro-level economic impacts. Therefore, this thesis aims to advance the Life Cycle Sustainability Assessment literature and electric vehicle sustainability research by presenting a novel combined application of Multi Criteria Decision Making techniques with Life Cycle Sustainability Assessment for decision analysis. With this motivation in mind, this research will construct a compromise-programming model (multi-objective optimization method) in order to calculate the optimum vehicle distribution in the U.S. passenger car fleet while considering the trade-offs between environmental, economic, and social dimensions of the sustainability. The findings of this research provide important insights for policy makers when developing strategies to estimate optimum vehicle distribution strategies based on various environmental and socio-economic priorities. For instance, compromise programming results can present practical policy conclusions for different states which might have different priorities for environmental impact mitigation and socio-economic development. Therefore, the conceptual framework presented in this work can be applicable for different regions in U.S. and decision makers can generate balanced policy conclusions and recommendations based on their environmental, economic and social constraints. The compromise programming results provide vital guidance for policy makers when optimizing the use of alternative vehicle technologies based on different environmental and socio-economic priorities. This research also effort aims to increase awareness of the inherent benefits of Input-Output based a Life Cycle Sustainability Assessment and multi-criteria optimization.
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Date Issued
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2015
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Identifier
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CFE0005858, ucf:50901
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0005858
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Title
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Data-driven Predictive Analytics For Distributed Smart Grid Control: Optimization of Energy Storage, Voltage and Demand Response.
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Creator
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Valizadehhaghi, Hamed, Qu, Zhihua, Behal, Aman, Atia, George, Turgut, Damla, Pensky, Marianna, University of Central Florida
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Abstract / Description
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The smart grid is expected to support an interconnected network of self-contained microgrids. Nonetheless, the distributed integration of renewable generation and demand response adds complexity to the control and optimization of smart grid. Forecasts are essential due to the existence of stochastic variations and uncertainty. Forecasting data are spatio-temporal which means that the data correspond to regular intervals, say every hour, and the analysis has to take account of spatial...
Show moreThe smart grid is expected to support an interconnected network of self-contained microgrids. Nonetheless, the distributed integration of renewable generation and demand response adds complexity to the control and optimization of smart grid. Forecasts are essential due to the existence of stochastic variations and uncertainty. Forecasting data are spatio-temporal which means that the data correspond to regular intervals, say every hour, and the analysis has to take account of spatial dependence among the distributed generators or locations. Hence, smart grid operations must take account of, and in fact benefit from the temporal dependence as well as the spatial dependence. This is particularly important considering the buffering effect of energy storage devices such as batteries, heating/cooling systems and electric vehicles. The data infrastructure of smart grid is the key to address these challenges, however, how to utilize stochastic modeling and forecasting tools for optimal and reliable planning, operation and control of smart grid remains an open issue.Utilities are seeking to become more proactive in decision-making, adjusting their strategies based on realistic predictive views into the future, thus allowing them to side-step problems and capitalize on the smart grid technologies, such as energy storage, that are now being deployed atscale. Predictive analytics, capable of managing intermittent loads, renewables, rapidly changing weather patterns and other grid conditions, represent the ultimate goal for smart grid capabilities.Within this framework, this dissertation develops high-performance analytics, such as predictive analytics, and ways of employing analytics to improve distributed and cooperative optimization software which proves to be the most significant value-add in the smart grid age, as new network management technologies prove reliable and fundamental. Proposed optimization and control approaches for active and reactive power control are robust to variations and offer a certain level of optimality by combining real-time control with hours-ahead network operation schemes. The main objective is managing spatial and temporal availability of the energy resources in different look-ahead time horizons. Stochastic distributed optimization is realized by integrating a distributed sub-gradient method with conditional ensemble predictions of the energy storage capacity and distributed generation. Hence, the obtained solutions can reflect on the system requirements for the upcoming times along with the instantaneous cooperation between distributed resources. As an important issue for smart grid, the conditional ensembles are studied for capturing wind, photovoltaic, and vehicle-to-grid availability variations. The following objectives are pursued:- Spatio-temporal adaptive modeling of data including electricity demand, electric vehicles and renewable energy (wind and solar power)- Predictive data analytics and forecasting- Distributed control- Integration of energy storage systemsFull distributional characterization and spatio-temporal modeling of data ensembles are utilized in order to retain the conditional and temporal interdependence between projection data and available capacity. Then, by imposing measures of the most likely ensembles, the distributed control method is carried out for cooperative optimization of the renewable generation and energy storage within the smart grid.
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Date Issued
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2016
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Identifier
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CFE0006408, ucf:51481
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0006408
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Title
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Forced Convection Cooling of Electric Motors Using Enhanced Surfaces.
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Creator
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Almaghrabi, Mohammed, Chow, Louis, Kassab, Alain, Das, Tuhin, University of Central Florida
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Abstract / Description
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Electric motors are extensively engaged in industrial and commercial applications such as electrical cars, energy-conversion systems, elevators, and actuators for aircrafts. Due to the significant internal heat generation, it is usually a challenge to design and manufacture high power density, high reliability, and low cost electric motors with superior performance. One of the efficient ways to dissipate the heat generated in the electrical motor is by using extended surfaces (i.e. heat sinks...
Show moreElectric motors are extensively engaged in industrial and commercial applications such as electrical cars, energy-conversion systems, elevators, and actuators for aircrafts. Due to the significant internal heat generation, it is usually a challenge to design and manufacture high power density, high reliability, and low cost electric motors with superior performance. One of the efficient ways to dissipate the heat generated in the electrical motor is by using extended surfaces (i.e. heat sinks). These surfaces are extruded from the motor casing and air is forced though them by a cooling fan. This cooling approach is simple to be implemented and has zero carbon emission to the environment. Adding ribs on the motor extended surface enhances the heat dissipation rate. This project is intended to study numerically the effect of varying ribs spacing and ribs heights on heat removal efficiency, accounting for the relative change in heat transfer coefficient and pressure drop compared to those for a smooth flow channel. The study is conducted to simulate the airflow field, and heat transfer for a plate heat sink using ANSYS V.16.The domain considered in the present work is a simple design of an electric motor annulus. The electric motor annulus consists of an array of ribbed fins. Heat source is represented as a uniform heat flux of 12250 W/m2 at the bottom surface of the heat sink base. Through the simulations, the rib heights (e=0.05, 0.1, 0.2, in mm) and spacing (p=1, 2,3,4,5, in mm) between the ribs, the channel width (Wch= 2 and 6 in mm), and the rib configuration (continues and inline ribs) are varied to study their effect on the performance of the heat sink for a Reynolds number range from 3133 to 12532. To assess which rib configuration is best, a figure of merit (named as thermal-hydraulic performance) is used which is defined as the ratio of heat transfer enhancement to the increase in pumping power due to the presence of the ribs. The highest thermal-hydraulic performance value out of all the transverse cases at Wch=2 mm in this study was 1.07 at e=0.05 mm, p=4 mm, and Re=3133 which means only a 7% enhancement is obtained. These set of cases are suitable for increasing the rate of heat transfer while ignoring the pressure drop penalty. Changing the channel width to 6 mm increases the thermal-hydraulic performance by about 23%. Therefore, this channel width is used for the inline ribs configurations with seven different opening ratios (10% to 70%). The inline ribs are investigated at two different Reynolds number (3133 and 12532). At an opening ratio of 50% the highest thermal-hydraulic performance of 1.18 and 1.22 were found at Re=3133 and p=5 mm, and at Re=3133 and p=1 mm, respectively. These simulation results show that with proper channel and ribs configuration, one can achieve about 22% increase in the thermal-hydraulic performance ratio over that of the smooth channel.
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Date Issued
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2016
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Identifier
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CFE0006433, ucf:51484
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0006433
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Title
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Multi-Physics Model of Key Components In High Efficiency Vehicle Drive.
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Creator
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Lin, Shao Hua, Wu, Xinzhang, Sundaram, Kalpathy, Wahid, Parveen, Wei, Lei, Chow, Louis, University of Central Florida
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Abstract / Description
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Hybrid Electric Vehicles (HEVs) and Electric Vehicles (EVs) are crucial technologies for the automotive industry to meet society's demands for cleaner, more energy efficient transportation. Meeting the need to provide power which sustains HEVs and EVs is an immediate area of concern that research and development within the automotive community must address. Electric batteries and electrical motors are the key components in HEV and EV power generation and transmission, and their performance...
Show moreHybrid Electric Vehicles (HEVs) and Electric Vehicles (EVs) are crucial technologies for the automotive industry to meet society's demands for cleaner, more energy efficient transportation. Meeting the need to provide power which sustains HEVs and EVs is an immediate area of concern that research and development within the automotive community must address. Electric batteries and electrical motors are the key components in HEV and EV power generation and transmission, and their performance plays very important role in the overall performance of the modern high efficiency vehicles. Therefore, in this dissertation, we are motivated to study the electric batteries, interior permanent motor (IPM), in the context of modern hybrid electric/electric drive systems, from both multi-physics and system level perspectives. Electrical circuit theory, electromagnetic Finite Element Analysis (FEA), and Computational Fluid Dynamic (CFD) finite volume method will be used primarily in this work. The work has total of five parts, and they are introduced in the following.Firstly, Battery thermal management design is critical in HEV and EV development. Accurate temperature distribution of the battery cells during vehicle operation is required for achieving optimized design. We propose a novel electrical-thermal battery modeling technique that couples a temperature dependent battery circuit model and a physics-based CFD model to meet this need. The electrical circuit model serves as a heat generation mechanism for the CFD model, and the CFD model provides the temperature distribution of the battery cells, which can also impact the heat generation of the electrical battery model. In this part of work, simulation data has been derived from the model respective to electrical performance of the battery as well as the temperature distribution simultaneously in consideration of the physical dimensions, material properties, and cooling conditions. The proposed model is validated against a battery model that couples the same electrical model with a known equivalent thermal model.Secondly, we propose an accurate system level Foster network thermal model. The parameters of the model are extracted from step responses of the CFD battery thermal model. The Foster network model and the CFD model give the same results. The Foster network can couple with battery circuit model to form an electric-thermal battery model for system simulation.Thirdly, IPM electric machines are important in high performance drive systems. During normal operations, irreversible demagnetization can occur due to temperature rise and various loading conditions. We investigate the performance of an IPM using 3d time stepping electromagnetic FEA considering magnet's temperature dependency. Torque, flux linkage, induced voltage, inductance and saliency of the IPM will be studied in details. Finally, we use CFD to predict the non-uniform temperature distribution of the IPM machine and the impact of this distribution on motor performance. Fourthly, we will switch gear to investigate the IPM motor on the system level. A reduced order IPM model is proposed to consider the effect of demagnetization of permanent magnet due to temperature effect. The proposed model is validated by comparing its results to the FEA results.Finally, a HEV is a vehicle that has both conventional mechanical (i.e. internal combustion engine) and electrical propulsion systems. The electrical powertrain is used to work with the conventional powertrain to achieve higher fuel economy and lower emissions. Computer based modeling and simulation techniques are therefore essential to help reduce the design cost and optimize system performance. Due to the complexity of hybrid vehicles, multi-domain modeling ability is preferred for both component modeling and system simulation. We present a HEV library developed using VHDL-AMS.
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Date Issued
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2013
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Identifier
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CFE0005024, ucf:50016
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0005024
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Title
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Electrical Conductivity Imaging via Boundary Value Problems for the 1-Laplacian.
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Creator
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Veras, Johann, Tamasan, Alexandru, Mohapatra, Ram, Nashed, M, Dogariu, Aristide, University of Central Florida
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Abstract / Description
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We study an inverse problem which seeks to image the internal conductivity map of a body by one measurement of boundary and interior data. In our study the interior data is the magnitude of the current density induced by electrodes. Access to interior measurements has been made possible since the work of M. Joy et al. in early 1990s and couples two physical principles: electromagnetics and magnetic resonance. In 2007 Nachman et al. has shown that it is possible to recover the conductivity...
Show moreWe study an inverse problem which seeks to image the internal conductivity map of a body by one measurement of boundary and interior data. In our study the interior data is the magnitude of the current density induced by electrodes. Access to interior measurements has been made possible since the work of M. Joy et al. in early 1990s and couples two physical principles: electromagnetics and magnetic resonance. In 2007 Nachman et al. has shown that it is possible to recover the conductivity from the magnitude of one current density field inside. The method now known as Current Density Impedance Imaging is based on solving boundary value problems for the 1-Laplacian in an appropriate Riemann metric space. We consider two types of methods: the ones based on level sets and a variational approach, which aim to solve specific boundary value problem associated with the 1-Laplacian. We will address the Cauchy and Dirichlet problems with full and partial data, and also the Complete Electrode Model (CEM). The latter model is known to describe most accurately the voltage potential distribution in a conductive body, while taking into account the transition of current from the electrode to the body. For the CEM the problem is non-unique. We characterize the non-uniqueness, and explain which additional measurements fix the solution. Multiple numerical schemes for each of the methods are implemented to demonstrate the computational feasibility.
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Date Issued
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2014
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Identifier
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CFE0005437, ucf:50388
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0005437
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Title
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Structure and Properties of Polymer-Derived SiBCN Ceramics.
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Creator
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Chen, Yaohan, An, Linan, Fang, Jiyu, Xu, Chengying, Zhai, Lei, Huo, Qun, Gong, Xun, University of Central Florida
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Abstract / Description
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Polymer-derived ceramics (PDCs) are a unique class of multifunctional materials synthesized by thermal decomposition of polymeric precursors. Due to their unique and excellent properties and flexible manufacturing capability, PDC is a promising technology to prepare ceramic fibers, coatings, composites and micro-sensors for high-temperature applications. However, the structure-property relationships of PDCs have not been well understood. The lack of such understandings drastically limited the...
Show morePolymer-derived ceramics (PDCs) are a unique class of multifunctional materials synthesized by thermal decomposition of polymeric precursors. Due to their unique and excellent properties and flexible manufacturing capability, PDC is a promising technology to prepare ceramic fibers, coatings, composites and micro-sensors for high-temperature applications. However, the structure-property relationships of PDCs have not been well understood. The lack of such understandings drastically limited the further developments and applications of the materials.In this dissertation, the structure and properties of amorphous polymer-derived silicon carbonitride (SiCN) and silicoboron carbonitride (SiBCN) have been studied. The SiCN was obtained using commercially available polysilazane as pre-ceramic precursor, and the SiBCN ceramics with varied Si-to-B ratio were obtained from polyborosilazanes, which were synthesized by the hydroboration and dehydrocoupling reaction of borane and polysilazane. The structural evolution of polymer-derived SiCN and SiBCN ceramics from polymer to ceramics was investigated by NMR, FTIR, Raman, EPR, TG/DTA, and XRD. The results show a phase-separation of amorphous matrix and a graphitization of (")free(") carbon phase, and suggest that the boron doping has a great influence on the structural evolution. The electric and dielectric properties of the SiCN and SiBCNs were studied by I-V curves, LCR Meter, and network analyzer. A new electronic conduction mechanism and structure model has been proposed to account for the relationships between the observed properties and microstructure of the materials. Furthermore, the SiBCN ceramics showed the improved dielectric properties at characterization temperature up to 1300 (&)#186;C, which allows the fabrication of ultrahigh-temperature wireless microsensors for extreme environments.
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Date Issued
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2012
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Identifier
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CFE0004195, ucf:49014
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0004195
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Title
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Growth and doping of MoS2 thin films for electronic and optoelectronic applications.
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Creator
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Abouelkhair, Hussain, Peale, Robert, Kaden, William, Stolbov, Sergey, Coffey, Kevin, University of Central Florida
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Abstract / Description
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MoS2 high absorption coefficient, high mobility, mechanical flexibility, and chemical inertness is very promising for many electronic and optoelectronic applications. The growth of high-quality MoS2 by a scalable and doping compatible method is still lacking. Therefore, the suitable dopants for MoS2 are not fully explored yet. This dissertation consists mainly of four main studies. The first study is on the growth of MoS2 thin films by atmospheric pressure chemical vapor deposition. Scanning...
Show moreMoS2 high absorption coefficient, high mobility, mechanical flexibility, and chemical inertness is very promising for many electronic and optoelectronic applications. The growth of high-quality MoS2 by a scalable and doping compatible method is still lacking. Therefore, the suitable dopants for MoS2 are not fully explored yet. This dissertation consists mainly of four main studies. The first study is on the growth of MoS2 thin films by atmospheric pressure chemical vapor deposition. Scanning electron microscope images revealed the growth of microdomes of MoS2 on top of a smooth MoS2 film. These microdomes are very promising as a broadband omnidirectional light trap for light harvesting applications. The second study is on the growth of MoS2 thin films by low pressure chemical vapor deposition (LPCVD). Control of sulfur vapor flow is essential for the growth of a pure phase of MoS2. Turning off sulfur vapor flow during the cooling cycle at 700 (&)#186;C leads to the growth of highly textured MoS2 with a Hall mobility of 20 cm2/Vs. The third study was on the growth of Ti-doped MoS2 thin films by LPCVD. The successful doping was confirmed by Hall effect measurement and secondary ion mass spectrometry (SIMS). Different growth temperatures from 1000 to 700 ? were studied. Ti act as a donor in MoS2. The fourth study is on fluorine-doped SnO2 (FTO) which has many technological applications including solar cells and transistors. FTO was grown by an aqueous-spray-based method. The main objective was to compare the actual against the nominal concentration of fluorine using SIMS. The concentration of fluorine in the grown films is lower than the concentration of fluorine in the aqueous solution.?
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Date Issued
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2017
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Identifier
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CFE0006847, ucf:51767
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0006847
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Title
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LDMOS Power Transistor Design and Evaluation using 2D and 3D Device Simulation.
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Creator
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Salih, Aiman, Yuan, Jiann-Shiun, Sundaram, Kalpathy, Kapoor, Vikram, University of Central Florida
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Abstract / Description
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The benefit of the super-junction (SJ) technique and the use of a floating P layer for low voltage (30 V) laterally double-diffused metal oxide semiconductor (LDMOS) transistors are investigated in this thesis using Sentaurus TCAD simulation software. Optimizations to the SJ LDMOS were attempted such as adding a buffer layer to the device, but simulation and theoretical evidence point out that the benefits of the SJ technique are marginal at the 30 V application. A replacement for the SJ...
Show moreThe benefit of the super-junction (SJ) technique and the use of a floating P layer for low voltage (30 V) laterally double-diffused metal oxide semiconductor (LDMOS) transistors are investigated in this thesis using Sentaurus TCAD simulation software. Optimizations to the SJ LDMOS were attempted such as adding a buffer layer to the device, but simulation and theoretical evidence point out that the benefits of the SJ technique are marginal at the 30 V application. A replacement for the SJ technique was sought, the floating P structure proved to be a good solution at the low voltage range due to its simpler cost effective process and performance gains achieved with optimization. A new idea of combining the floating P layer with shallow trench isolation is simulated yielding a low figure of merit (on state resistance (&)#215; gate charge) of 5.93 m?-nC.
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Date Issued
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2017
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Identifier
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CFE0006955, ucf:51673
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0006955
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Title
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Investigation on electrical properties of RF sputtered deposited BCN thin films.
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Creator
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Prakash, Adithya, Sundaram, Kalpathy, Yuan, Jiann-Shiun, Lin, Mingjie, University of Central Florida
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Abstract / Description
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The ever increasing advancements in semiconductor technology and continuous scaling of CMOS devices mandate the need for new dielectric materials with low-k values. The interconnect delay can be reduced not only by the resistance of the conductor but also by decreasing the capacitance of dielectric layer. Also cross-talk is a major issue faced by semiconductor industry due to high value of k of the inter-dielectric layer (IDL) in a multilevel wiring scheme in Si ultra large scale integrated...
Show moreThe ever increasing advancements in semiconductor technology and continuous scaling of CMOS devices mandate the need for new dielectric materials with low-k values. The interconnect delay can be reduced not only by the resistance of the conductor but also by decreasing the capacitance of dielectric layer. Also cross-talk is a major issue faced by semiconductor industry due to high value of k of the inter-dielectric layer (IDL) in a multilevel wiring scheme in Si ultra large scale integrated circuit (ULSI) devices. In order to reduce the time delay, it is necessary to introduce a wiring metal with low resistivity and a high quality insulating film with a low dielectric constant which leads to a reduction of the wiring capacitance.Boron carbon nitride (BCN) films are prepared by reactive magnetron sputtering from a B(&)#172;4C target and deposited to make metal-insulator-metal (MIM) sandwich structures using aluminum as the top and bottom electrodes. BCN films are deposited at various N2/Ar gas flow ratios, substrate temperatures and process pressures. The electrical characterization of the MIM devices includes capacitance vs. voltage (C-V), current vs voltage, and breakdown voltage characteristics. The above characterizations are performed as a function of deposition parameters.
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Date Issued
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2013
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Identifier
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CFE0004912, ucf:49625
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0004912
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Title
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ANALYSIS OF TIME SYNCHRONIZATION ERRORS IN HIGH DATA RATE ULTRAWIDEBAND ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING DATA LINKS.
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Creator
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Bates, Lakesha, Jones, W. Linwood, University of Central Florida
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Abstract / Description
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Emerging Ultra Wideband (UWB) Orthogonal Frequency Division Multiplexing (OFDM) systems hold the promise of delivering wireless data at high speeds, exceeding hundreds of megabits per second over typical distances of 10 meters or less. The purpose of this Thesis is to estimate the timing accuracies required with such systems in order to achieve Bit Error Rates (BER) of the order of magnitude of 10-12 and thereby avoid overloading the correction of irreducible errors due to misaligned timing...
Show moreEmerging Ultra Wideband (UWB) Orthogonal Frequency Division Multiplexing (OFDM) systems hold the promise of delivering wireless data at high speeds, exceeding hundreds of megabits per second over typical distances of 10 meters or less. The purpose of this Thesis is to estimate the timing accuracies required with such systems in order to achieve Bit Error Rates (BER) of the order of magnitude of 10-12 and thereby avoid overloading the correction of irreducible errors due to misaligned timing errors to a small absolute number of bits in error in real-time relative to a data rate of hundreds of megabits per second. Our research approach involves managing bit error rates through identifying maximum timing synchronization errors. Thus, it became our research goal to determine the timing accuracies required to avoid operation of communication systems within the asymptotic region of BER flaring at low BERs in the resultant BER curves. We propose pushing physical layer bit error rates to below 10-12 before using forward error correction (FEC) codes. This way, the maximum reserve is maintained for the FEC hardware to correct for burst as well as recurring bit errors due to corrupt bits caused by other than timing synchronization errors.
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Date Issued
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2004
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Identifier
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CFE0000197, ucf:46173
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0000197
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Title
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Driving Towards Sustainability: A Case Study of the Facilitators and Inhibitors of Electrifying Drive Tourism within the United States National Park System.
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Creator
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Templeton, Amanda, Fjelstul, Jill, Fyall, Alan, Tasci, Asli, Prideaux, Bruce, University of Central Florida
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Abstract / Description
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Drive tourism has proven to be a popular sub-sector of the tourism industry, given its ability to offer tourists a substantial amount of flexibility and sense of freedom in determining what destinations to explore. Few studies have examined the future of the drive tourism with consideration to changing technologies and growing awareness to the impact of carbon emissions and Green House Gasses. Research has recently begun to examine the ecological consequences of park transportation systems....
Show moreDrive tourism has proven to be a popular sub-sector of the tourism industry, given its ability to offer tourists a substantial amount of flexibility and sense of freedom in determining what destinations to explore. Few studies have examined the future of the drive tourism with consideration to changing technologies and growing awareness to the impact of carbon emissions and Green House Gasses. Research has recently begun to examine the ecological consequences of park transportation systems. Some of these problems can be seen within the United States National Park System (NPS), as various park units are experiencing problems related to infrastructure and preservation of sites. As transportation plays an integral role within the NPS, the impacts of drive tourism must be considered. The study is founded on the premise that electric vehicles and electric vehicle charging stations will reduce GHG emissions, thereby increasing sustainability, supporting sustainable tourism and sustainable drive tourism within the NPS. In an effort to promote sustainable transportation efforts throughout the NPS this study investigates the facilitators that enable an EV infrastructure in some parks and inhibitors for other parks that have yet to develop an EV infrastructure. A qualitative methodology was adopted for this study. Data were analyzed using NVivo with findings being presented in case study format. The study, which offers a conceptual model and offers new definitions for electric vehicles and electric vehicle infrastructure within nature based tourism context, finds key facilitators to include: collaborative efforts through public/private partnerships, strong leadership within the NPS, and availability of funding; major inhibitors being: geography of park unit, lack cultural openness within NPS park unit, and regulatory policies. Current research has given little attention to the future sustainability of drive tourism, allowing this study to add to the academic body of knowledge. Additionally, the suggestions offered in the study are relevantly timed to what is happening within the industry.
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Date Issued
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2018
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Identifier
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CFE0007107, ucf:51967
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0007107
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Title
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Optical Properties of Single Nanoparticles and Two-dimensional Arrays of Plasmonic Nanostructures.
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Creator
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Zhou, Yadong, Zou, Shengli, Harper, James, Zhai, Lei, Chen, Gang, Zheng, Qipeng, University of Central Florida
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Abstract / Description
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The tunability of plasmonic properties of nanomaterials makes them promising in many applications such as molecular detection, spectroscopy techniques, solar energy materials, etc. In the thesis, we mainly focus on the interaction between light with single nanoparticles and two-dimensional plasmonic nanostructures using electrodynamic methods. The fundamental equations of electromagnetic theory: Maxwell's equations are revisited to solve the problems of light-matter interaction, particularly...
Show moreThe tunability of plasmonic properties of nanomaterials makes them promising in many applications such as molecular detection, spectroscopy techniques, solar energy materials, etc. In the thesis, we mainly focus on the interaction between light with single nanoparticles and two-dimensional plasmonic nanostructures using electrodynamic methods. The fundamental equations of electromagnetic theory: Maxwell's equations are revisited to solve the problems of light-matter interaction, particularly the interaction of light and noble nanomaterials, such as gold and silver. In Chapter 1, Stokes parameters that describe the polarization states of electromagnetic wave are presented. The scattering and absorption of a particle with an arbitrary shape are discussed. In Chapter 2, several computational methods for solving the optical response of nanomaterials when they are illuminated by incident light are studied, which include the Discrete Dipole Approximation (DDA) method, the coupled dipole (CD) method, etc. In Chapter 3, the failure and reexamination of the relation between the Raman enhancement factor and local enhanced electric field intensity is investigated by placing a molecular dipole in the vicinity of a silver rod. Using a silver rod and a molecular dipole, we demonstrate that the relation generated using a spherical nanoparticle cannot simply be applied to systems with particles of different shapes. In Chapter 4, a silver film with switchable total transmission/reflection is discussed. The film is composed of two-dimensional rectangular prisms. The factors affecting the transmission (reflection) as well as the mechanisms leading to the phenomena are studied. Later, in Chapter 5 and 6, the sandwiched nano-film composed of two 2D rectangular prisms arrays and two glass substrates with a continuous film in between is examined to enhance the transmission of the continuous silver film.
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Date Issued
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2018
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Identifier
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CFE0007117, ucf:51943
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0007117
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Title
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Development of Regional Optimization and Market Penetration Models For the Electric Vehicles in the United States.
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Creator
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Noori, Mehdi, Tatari, Omer, Oloufa, Amr, Nam, Boo Hyun, Xanthopoulos, Petros, University of Central Florida
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Abstract / Description
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Since the transportation sector still relies mostly on fossil fuels, the emissions and overall environmental impacts of the transportation sector are particularly relevant to the mitigation of the adverse effects of climate change. Sustainable transportation therefore plays a vital role in the ongoing discussion on how to promote energy insecurity and address future energy requirements. One of the most promising ways to increase energy security and reduce emissions from the transportation...
Show moreSince the transportation sector still relies mostly on fossil fuels, the emissions and overall environmental impacts of the transportation sector are particularly relevant to the mitigation of the adverse effects of climate change. Sustainable transportation therefore plays a vital role in the ongoing discussion on how to promote energy insecurity and address future energy requirements. One of the most promising ways to increase energy security and reduce emissions from the transportation sector is to support alternative fuel technologies, including electric vehicles (EVs). As vehicles become electrified, the transportation fleet will rely on the electric grid as well as traditional transportation fuels for energy. The life cycle cost and environmental impacts of EVs are still very uncertain, but are nonetheless extremely important for making policy decisions. Moreover, the use of EVs will help to diversify the fuel mix and thereby reduce dependence on petroleum. In this respect, the United States has set a goal of a 20% share of EVs on U.S. roadways by 2030. However, there is also a considerable amount of uncertainty in the market share of EVs that must be taken into account. This dissertation aims to address these inherent uncertainties by presenting two new models: the Electric Vehicles Regional Optimizer (EVRO), and Electric Vehicle Regional Market Penetration (EVReMP). Using these two models, decision makers can predict the optimal combination of drivetrains and the market penetration of the EVs in different regions of the United States for the year 2030.First, the life cycle cost and life cycle environmental emissions of internal combustion engine vehicles, gasoline hybrid electric vehicles, and three different EV types (gasoline plug-in hybrid EVs, gasoline extended-range EVs, and all-electric EVs) are evaluated with their inherent uncertainties duly considered. Then, the environmental damage costs and water footprints of the studied drivetrains are estimated. Additionally, using an Exploratory Modeling and Analysis method, the uncertainties related to the life cycle costs, environmental damage costs, and water footprints of the studied vehicle types are modeled for different U.S. electricity grid regions. Next, an optimization model is used in conjunction with this Exploratory Modeling and Analysis method to find the ideal combination of different vehicle types in each U.S. region for the year 2030. Finally, an agent-based model is developed to identify the optimal market shares of the studied vehicles in each of 22 electric regions in the United States. The findings of this research will help policy makers and transportation planners to prepare our nation's transportation system for the future influx of EVs.The findings of this research indicate that the decision maker's point of view plays a vital role in selecting the optimal fleet array. While internal combustion engine vehicles have the lowest life cycle cost, the highest environmental damage cost, and a relatively low water footprint, they will not be a good choice in the future. On the other hand, although all-electric vehicles have a relatively low life cycle cost and the lowest environmental damage cost of the evaluated vehicle options, they also have the highest water footprint, so relying solely on all-electric vehicles is not an ideal choice either. Rather, the best fleet mix in 2030 will be an electrified fleet that relies on both electricity and gasoline. From the agent-based model results, a deviation is evident between the ideal fleet mix and that resulting from consumer behavior, in which EV shares increase dramatically by the year 2030 but only dominate 30 percent of the market. Therefore, government subsidies and the word-of-mouth effect will play a vital role in the future adoption of EVs.
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Date Issued
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2015
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Identifier
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CFE0005852, ucf:50927
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0005852
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Title
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High performance liquid crystal devices for augmented reality and virtual reality.
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Creator
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Talukder, Md Javed Rouf, Wu, Shintson, Moharam, Jim, Amezcua Correa, Rodrigo, Dong, Yajie, University of Central Florida
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Abstract / Description
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See-through augmented reality and virtual reality displays are emerging due to their widespread applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment. For augmented reality and virtual reality displays, high-resolution density, high luminance, fast response time and high ambient contrast ratio are critically needed. High-resolution density helps eliminate the screen-door effect, high luminance and fast response time...
Show moreSee-through augmented reality and virtual reality displays are emerging due to their widespread applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment. For augmented reality and virtual reality displays, high-resolution density, high luminance, fast response time and high ambient contrast ratio are critically needed. High-resolution density helps eliminate the screen-door effect, high luminance and fast response time enable low duty ratio operation, which plays a key role for suppressing image blurs. A dimmer placed in front of AR display helps to control the incident background light, which in turn improves the image contrast. In this dissertation, we have focused three crucial display metrics: high luminance, fast motion picture response time (MPRT) and high ambient contrast ratio.We report a fringe-field switching liquid crystal display, abbreviated as d-FFS LCD, by using a low viscosity material and new diamond-shape electrode configuration. Our proposed device shows high transmittance, fast motion picture response time, low operation voltage, wide viewing angle, and indistinguishable color shift and gamma shift. We also investigate the rubbing angle effects on transmittance and response time. When rubbing angle is 0 degree, the virtual wall effect is strong, resulting in fast response time but compromised transmittance. When rubbing angle is greater than 1.2 degree, the virtual walls disappear, as a result, the transmittance increases dramatically, but the tradeoff is in slower response time. We also demonstrate a photo-responsive guest-host liquid crystal (LC) dimmer to enhance the ambient contrast ratio in augmented reality displays. The LC composition consists of photo-stable chiral agent, photosensitive azobenzene, and dichroic dye in a nematic host with negative dielectric anisotropy. In this device, transmittance changes from bright state to dark state by exposing a low intensity UV or blue light. Reversal process can be carried out by red light or thermal effect. Such a polarizer-free photo-activated dimmer can also be used for wide range of applications, such as diffractive photonic devices, portable information system, vehicular head-up displays, and smart window for energy saving purpose. A dual-stimuli polarizer-free dye-doped liquid crystal (LC) device is demonstrated as a dimmer. Upon UV/blue light exposure, the LC directors and dye molecules turn from initially vertical alignment (high transmittance state) to twisted fingerprint structure (low transmittance state). The reversal process is accelerated by combining a longitudinal electric field to unwind the LC directors from twisted fingerprint to homeotropic state, and a red light to transform the cis azobenzene back to trans. Such an electric-field-assisted reversal time can be reduced from ~10s to a few milliseconds, depending on the applied voltage. Considering power consumption, low manufacturing cost, and large fabrication tolerance, this device can be used as a smart dimmer to enhance the ambient contrast ratio for augmented reality displays.
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Date Issued
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2019
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Identifier
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CFE0007731, ucf:52425
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0007731
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Title
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Reproductive life history and signal evolution in a multi-species assemblage of electric fish.
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Creator
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Waddell, Joseph, Crampton, William, Fedorka, Kenneth, Quintana-Ascencio, Pedro, Stoddard, Philip, University of Central Florida
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Abstract / Description
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Animals that co-occur in sympatry with multiple closely-related species use reproductive mate attraction signals not only to assess the quality of a potential conspecific mate (sexual selection), but also to discriminate conspecifics from heterospecifics (species recognition). However, the extent to which sexual selection and species recognition may interact, or even conflict, is poorly known. Neotropical electric fish offer unrivaled opportunities for understanding this problem. They...
Show moreAnimals that co-occur in sympatry with multiple closely-related species use reproductive mate attraction signals not only to assess the quality of a potential conspecific mate (sexual selection), but also to discriminate conspecifics from heterospecifics (species recognition). However, the extent to which sexual selection and species recognition may interact, or even conflict, is poorly known. Neotropical electric fish offer unrivaled opportunities for understanding this problem. They generate simple, stereotyped mate attraction signals that are easy to record and quantify, and that are well-understood from the neurobiological perspective. Additionally, they live in electrically-crowded environments, where multiple congeners live and reproduce in close proximity. This dissertation reports an investigation of electric signal diversity and reproductive life history in a nine-species assemblage of the electric fish genus Brachyhypopomus from the upper Amazon. A year-long quantitative sampling program yielded a library of electric signal recordings from (>)3,000 individuals and an accompanying collection of preserved specimens from which suites of informative life history traits were measured. These data were used to understand basic reproductive biology, and to describe sexually dimorphic and interspecific diversity in electric signals. By integrating approaches from ecology, physiology, and evolutionary biology, novel perspectives are provided on: 1. how sexual selection and species recognition interact to shape signal diversity and the occupation of signal space in multi-species animal communities; 2. how extreme seasonal variation in Amazonian ecosystems influences trade-offs in the allocation of reproductive resources (-) including mate attraction signals, and; 3. how environmental variation shapes general life-history traits in a diverse tropical animal assemblage.
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Date Issued
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2017
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Identifier
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CFE0006925, ucf:51689
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0006925
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Title
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Nonlinear dynamic modeling, simulation and characterization of the mesoscale neuron-electrode interface.
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Creator
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Thakore, Vaibhav, Hickman, James, Mucciolo, Eduardo, Rahman, Talat, Johnson, Michael, Behal, Aman, Molnar, Peter, University of Central Florida
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Abstract / Description
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Extracellular neuroelectronic interfacing has important applications in the fields of neural prosthetics, biological computation and whole-cell biosensing for drug screening and toxin detection. While the field of neuroelectronic interfacing holds great promise, the recording of high-fidelity signals from extracellular devices has long suffered from the problem of low signal-to-noise ratios and changes in signal shapes due to the presence of highly dispersive dielectric medium in the neuron...
Show moreExtracellular neuroelectronic interfacing has important applications in the fields of neural prosthetics, biological computation and whole-cell biosensing for drug screening and toxin detection. While the field of neuroelectronic interfacing holds great promise, the recording of high-fidelity signals from extracellular devices has long suffered from the problem of low signal-to-noise ratios and changes in signal shapes due to the presence of highly dispersive dielectric medium in the neuron-microelectrode cleft. This has made it difficult to correlate the extracellularly recorded signals with the intracellular signals recorded using conventional patch-clamp electrophysiology. For bringing about an improvement in the signal-to-noise ratio of the signals recorded on the extracellular microelectrodes and to explore strategies for engineering the neuron-electrode interface there exists a need to model, simulate and characterize the cell-sensor interface to better understand the mechanism of signal transduction across the interface. Efforts to date for modeling the neuron-electrode interface have primarily focused on the use of point or area contact linear equivalent circuit models for a description of the interface with an assumption of passive linearity for the dynamics of the interfacial medium in the cell-electrode cleft. In this dissertation, results are presented from a nonlinear dynamic characterization of the neuroelectronic junction based on Volterra-Wiener modeling which showed that the process of signal transduction at the interface may have nonlinear contributions from the interfacial medium. An optimization based study of linear equivalent circuit models for representing signals recorded at the neuron-electrode interface subsequently proved conclusively that the process of signal transduction across the interface is indeed nonlinear. Following this a theoretical framework for the extraction of the complex nonlinear material parameters of the interfacial medium like the dielectric permittivity, conductivity and diffusivity tensors based on dynamic nonlinear Volterra-Wiener modeling was developed. Within this framework, the use of Gaussian bandlimited white noise for nonlinear impedance spectroscopy was shown to offer considerable advantages over the use of sinusoidal inputs for nonlinear harmonic analysis currently employed in impedance characterization of nonlinear electrochemical systems. Signal transduction at the neuron-microelectrode interface is mediated by the interfacial medium confined to a thin cleft with thickness on the scale of 20-110 nm giving rise to Knudsen numbers (ratio of mean free path to characteristic system length) in the range of 0.015 and 0.003 for ionic electrodiffusion. At these Knudsen numbers, the continuum assumptions made in the use of Poisson-Nernst-Planck system of equations for modeling ionic electrodiffusion are not valid. Therefore, a lattice Boltzmann method (LBM) based multiphysics solver suitable for modeling ionic electrodiffusion at the mesoscale neuron-microelectrode interface was developed. Additionally, a molecular speed dependent relaxation time was proposed for use in the lattice Boltzmann equation. Such a relaxation time holds promise for enhancing the numerical stability of lattice Boltzmann algorithms as it helped recover a physically correct description of microscopic phenomena related to particle collisions governed by their local density on the lattice. Next, using this multiphysics solver simulations were carried out for the charge relaxation dynamics of an electrolytic nanocapacitor with the intention of ultimately employing it for a simulation of the capacitive coupling between the neuron and the planar microelectrode on a microelectrode array (MEA). Simulations of the charge relaxation dynamics for a step potential applied at t = 0 to the capacitor electrodes were carried out for varying conditions of electric double layer (EDL) overlap, solvent viscosity, electrode spacing and ratio of cation to anion diffusivity. For a large EDL overlap, an anomalous plasma-like collective behavior of oscillating ions at a frequency much lower than the plasma frequency of the electrolyte was observed and as such it appears to be purely an effect of nanoscale confinement. Results from these simulations are then discussed in the context of the dynamics of the interfacial medium in the neuron-microelectrode cleft. In conclusion, a synergistic approach to engineering the neuron-microelectrode interface is outlined through a use of the nonlinear dynamic modeling, simulation and characterization tools developed as part of this dissertation research.
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Date Issued
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2012
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Identifier
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CFE0004797, ucf:49718
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0004797
Pages