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Title: REDUCING SIDE-SWEEP ACCIDENTS WITH VEHICLE-to-VEHICLECOMMUNICATIONS.
Creator: Bulumulle, Gamini, Boloni, Ladislau, Sundaram, Kalpathy, Chatterjee, Mainak, Yuksel, Murat, Goldiez, Brian, University of Central Florida
Abstract / Description: This dissertation present contributions to the understanding of the causes of a side-sweep accidents on multi-lane highways using computer simulation. Side-sweep accidents are one of the major causes of loss of life and property damage on highways. This type of accident is caused by a driver initiating a lane change while another vehicle is blocking the road in the target lane.Our objective in the research described in this dissertation was to understand and simulate the different factors...
Show moreThis dissertation present contributions to the understanding of the causes of a side-sweep accidents on multi-lane highways using computer simulation. Side-sweep accidents are one of the major causes of loss of life and property damage on highways. This type of accident is caused by a driver initiating a lane change while another vehicle is blocking the road in the target lane.Our objective in the research described in this dissertation was to understand and simulate the different factors which affect the likelihood of side sweep accidents. For instance, we know that blind spots, parts of the road that are not visible to the driver directly or through the rear-view mirrors are often a contributing factor. Similarly, the frequency with which a driver checks his rear-view mirrors before initiating the lane change affects the likelihood of the accident. We can also have an intuition that side-sweep accidents are more likely if there is a significant difference in the vehicle velocities between the current and the target lanes. There are also factors that can reduce the likelihood of the accident: for instance, the signaling of the lane change by the driver can alert the nearby vehicles about the lane change, and they can change their behaviors to give way to the lane changing vehicle. The emerging technology of vehicle-to-vehicle communication offers promising new avenues to avoid such collisions by making vehicles communicate the lane change intent and their positions, such that automatic action can be taken to avoid the accident.While we can have an intuition about whether some factors increase or reduce accident rate, these factors interact with each other in complex ways. The research described in this dissertation developed a highway driving simulator specialized for the accurate simulation of the various factors which contribute to the act of lane change in highway driving. We are modeling the traffic as seen from the lane changing vehicle, including the density, distribution and relative velocity of the vehicles on the target lane. We are also modeling the geometry of the vehicle, including size, windows, mirrors, and blind spots. Moving to the human factors of the simulation, we are modeling the behavior of the driver with regards to the times of checking the mirrors, signalling and making the lane change decision. Finally, we are also modeling communication, both using the traditional way using the turn signals, as well as through means of automated vehicle to vehicle communication.The detailed modeling of these factors allowed us to perform extensive simulation studies that allow us to study the impact of various factors on the probability of side-sweep accidents.We validated the simulation models by comparing the results with the real-world observations of the National Highway Traffic Safety Administration. One of the benefits of our model is that it allows the modeling of the impact of vehicle to vehicle communication, a technology currently in prototype stage, that cannot be studied in extensive real world scenarios.
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Date Issued: 2017
Identifier: CFE0006570, ucf:51317
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006570

Title: Method for Derivation and Synthesis of Electromagnetic Environmental Effects Requirement Limits for Achieving System Level Electromagnetic Compatibility.
Creator: Freeman, Larry, Wu, Thomas, Wahid, Parveen, Wei, Lei, Sundaram, Kalpathy, Chow, Louis, University of Central Florida
Abstract / Description: As humans endeavor to build large-scale complex systems, it will necessitate the integration of engineering practices and techniques to allocate many of the design aspects and responsibility across traditional boundaries. Many of today's large-scale complex systems, like commercial aircraft, satellite systems, and even automobiles use parts from all over the world. A recently completed airframe, largest commercial aircraft in the world, took nearly 30 years to build, required over 400...
Show moreAs humans endeavor to build large-scale complex systems, it will necessitate the integration of engineering practices and techniques to allocate many of the design aspects and responsibility across traditional boundaries. Many of today's large-scale complex systems, like commercial aircraft, satellite systems, and even automobiles use parts from all over the world. A recently completed airframe, largest commercial aircraft in the world, took nearly 30 years to build, required over 400 different suppliers from 20 different countries. These kinds of projects dictate a method for derivation and synthesis of electromagnetic environmental effects (E3) requirement limits for achieving system level electromagnetic compatibility (EMC).If a system level EMC design is an assemblage of compliant subsystems, then the subsystems should be an assemblage of compliant module and component designs. This requires tailoring the system level requirements through to module or component level designs. The method discussed is applicable to a variety of designs across varying levels of complexity and importantly implementable early in the design process. The method provides rationale for derivation of limits while maintaining traceability to system level requirements. Specific examples using the four common divisions of EMC requirements, conducted emissions, radiated emissions, conducted susceptibility, and radiated susceptibility are included. An overall system engineering approach and formal methodology is included. Detailed comparison examples using commercial and military EMC requirements are also included. Lastly, a discussion is included on comparison and margin analysis of input filtering for verifying compliance to requirements at the system level.
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Date Issued: 2016
Identifier: CFE0006303, ucf:51603
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006303

Title: Analysis and Design Optimization of Multiphase Converter.
Creator: Zhang, Kejiu, Wu, Xinzhang, Batarseh, Issa, Yuan, Jiann-Shiun, Sundaram, Kalpathy, Chow, Louis, University of Central Florida
Abstract / Description: Future microprocessors pose many challenges to the power conversion techniques. Multiphase synchronous buck converters have been widely used in high current low voltage microprocessor application. Design optimization needs to be carefully carried out with pushing the envelope specification and ever increasing concentration towards power saving features. In this work, attention has been focused on dynamic aspects of multiphase synchronous buck design. The power related issues and optimizations...
Show moreFuture microprocessors pose many challenges to the power conversion techniques. Multiphase synchronous buck converters have been widely used in high current low voltage microprocessor application. Design optimization needs to be carefully carried out with pushing the envelope specification and ever increasing concentration towards power saving features. In this work, attention has been focused on dynamic aspects of multiphase synchronous buck design. The power related issues and optimizations have been comprehensively investigated in this paper. In the first chapter, multiphase DC-DC conversion is presented with background application. Adaptive voltage positioning and various nonlinear control schemes are evaluated. Design optimization are presented to achieve best static efficiency over the entire load range. Power loss analysis from various operation modes and driver IC definition are studied thoroughly to better understand the loss terms and minimize the power loss. Load adaptive control is then proposed together with parametric optimization to achieve optimum efficiency figure.New nonlinear control schemes are proposed to improve the transient response, i.e. load engage and load release responses, of the multiphase VR in low frequency repetitive transient. Drop phase optimization and PWM transition from long tri-state phase are presented to improve the smoothness and robustness of the VR in mode transition. During high frequency repetitive transient, the control loop should be optimized and nonlinear loop should be turned off. Dynamic current sharing are thoroughly studied in chapter 4. The output impedance of the multiphase synchronous buck are derived to assist the analysis. Beat frequency is studied and mitigated by proposing load frequency detection scheme by turning OFF the nonlinear loop and introducing current protection in the control loop.Dynamic voltage scaling (DVS) is now used in modern Multi-Core processor (MCP) and multiprocessor System-on-Chip (MPSoC) to reduce operational voltage under light load condition. With the aggressive motivation to boost dynamic power efficiency, the design specification of voltage transition (dv/dt) for the DVS is pushing the physical limitation of the multiphase converter design and the component stress as well. In this paper, the operation modes and modes transition during dynamic voltage transition are illustrated. Critical dead-times of driver IC design and system dynamics are first studied and then optimized. The excessive stress on the control MOSFET which increases the reliability concern is captured in boost mode operation. Feasible solutions are also proposed and verified by both simulation and experiment results. CdV/dt compensation for removing the AVP effect and novel nonlinear control scheme for smooth transition are proposed for dealing with fast voltage positioning. Optimum phase number control during dynamic voltage transition is also proposed and triggered by voltage identification (VID) delta to further reduce the dynamic loss. The proposed schemes are experimentally verified in a 200 W six phase synchronous buck converter.Finally, the work is concluded. The references are listed.
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Date Issued: 2013
Identifier: CFE0005079, ucf:50742
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005079

Title: RF Circuit Designs for Reliability and Process Variability Resilience.
Creator: Kritchanchai, Ekavut, Yuan, Jiann-Shiun, Sundaram, Kalpathy, Wei, Lei, Lin, Mingjie, Chow, Lee, University of Central Florida
Abstract / Description: Complementary metal oxide semiconductor (CMOS) radio frequency (RF) circuit design has been an ever-lasting research field. It has gained so much attention since RF circuits offer high mobility and wide-band efficiency, while CMOS technology provides the advantage of low cost and high integration capability. At the same time, CMOS device size continues to scale to the nanometer regime. Reliability issues with RF circuits have become more challenging than ever before. Reliability mechanisms,...
Show moreComplementary metal oxide semiconductor (CMOS) radio frequency (RF) circuit design has been an ever-lasting research field. It has gained so much attention since RF circuits offer high mobility and wide-band efficiency, while CMOS technology provides the advantage of low cost and high integration capability. At the same time, CMOS device size continues to scale to the nanometer regime. Reliability issues with RF circuits have become more challenging than ever before. Reliability mechanisms, such as gate oxide breakdown, hot carrier injection, negative bias temperature instability, have been amplified as the device size shrinks. In addition, process variability becomes a new design paradigm in modern RF circuits.In this Ph.D. work, a class F power amplifier (PA) was designed and analyzed using TSMC 180nm process technology. Its pre-layout and post-layout performances were compared. Post-layout parasitic effect decreases the output power and power-added efficiency. Physical insight of hot electron impact ionization and device self-heating was examined using the mixed-mode device and circuit simulation to mimic the circuit operating environment. Hot electron effect increases the threshold voltage and decreases the electron mobility of an n-channel transistor, which in turn decreases the output power and power-added efficiency of the power amplifier, as evidenced by the RF circuit simulation results. The device self-heating also reduces the output power and power-added efficiency of the PA. The process, voltage, and temperature (PVT) effects on a class AB power amplifier were studied. A PVT compensation technique using a current-source as an on-chip sensor was developed. The adaptive body bias design with the current sensing technique makes the output power and power-added efficiency much less sensitive to process variability, supply voltage variation, and temperature fluctuation, predicted by our derived analytical equations which are also verified by Agilent Advanced Design System (ADS) circuit simulation.Process variations and hot electron reliability on the mixer performance were also evaluated using different process corner models. The conversion gain and noise figure were modeled using analytical equations, supported by ADS circuit simulation results. A process invariant current source circuit was developed to eliminate process variation effect on circuit performance. Our conversion gain, noise figure, and output power show robust performance against PVT variations compared to those of a traditional design without using the current sensor, as evidenced by Monte Carlo statistical simulation.Finally, semiconductor process variations and hot electron reliability on the LC-voltage controlled oscillator (VCO) performance was evaluated using different process models. In our newly designed VCO, the phase noise and power consumptions are resilient against process variation effect due to the use of on-chip current sensing and compensation. Our Monte-Carlo simulation and analysis demonstrate that the standard deviation of phase noise in the new VCO design reduces about five times than that of the conventional design.
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Date Issued: 2016
Identifier: CFE0006131, ucf:51182
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006131

Title: Ultrafast Laser Material Processing For Photonic Applications.
Creator: Ramme, Mark, Richardson, Martin, Fathpour, Sasan, Sundaram, Kalpathy, Kar, Aravinda, University of Central Florida
Abstract / Description: Femtosecond Laser Direct Writing (FLDW) is a viable technique for producing photonic devices in bulk materials. This novel manufacturing technique is versatile due to its full 3D fabrication capability. Typically, the only requirement for this process is that the base material must be transparent to the laser wavelength. The modification process itself is based on non-linear energy absorption of laser light within the focal volume of the incident beam.This thesis addresses the feasibility of...
Show moreFemtosecond Laser Direct Writing (FLDW) is a viable technique for producing photonic devices in bulk materials. This novel manufacturing technique is versatile due to its full 3D fabrication capability. Typically, the only requirement for this process is that the base material must be transparent to the laser wavelength. The modification process itself is based on non-linear energy absorption of laser light within the focal volume of the incident beam.This thesis addresses the feasibility of this technique for introducing photonic structures into novel dielectric materials. Additionally, this work provides a deeper understanding of the light-matter interaction mechanism occurring at high pulse repetition rates. A novel structure on the sample surface in the form of nano-fibers was observed when the bulk material was irradiated with high repetition rate pulse trains.To utilize the advantages of the FLDW technique even further, a transfer of the technology from dielectric to semiconductor materials is investigated. However, this demands detailed insight of the absorption and modification processes themselves. Experiments and the results suggested that non-linear absorption, specifically avalanche ionization, is the limiting factor inhibiting the application of FLDW to bulk semiconductors with today's laser sources.
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Date Issued: 2013
Identifier: CFE0004914, ucf:49626
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004914

Title: rf power amplifier and oscillator design for reliability and variability.
Creator: Chen, Shuyu, Yuan, Jiann-Shiun, Sundaram, Kalpathy, Shen, Zheng, Gong, Xun, Wang, Morgan, University of Central Florida
Abstract / Description: CMOS RF circuit design has been an ever-lasting research field. It gained so much attention since RF circuits have high mobility and wide band efficiency, while CMOS technology has the advantage of low cost and better capability of integration. At the same time, IC circuits never stopped scaling down for the recent many decades. Reliability issues with RF circuits have become more and more severe with device scaling down: reliability effects such as gate oxide break down, hot carrier...
Show moreCMOS RF circuit design has been an ever-lasting research field. It gained so much attention since RF circuits have high mobility and wide band efficiency, while CMOS technology has the advantage of low cost and better capability of integration. At the same time, IC circuits never stopped scaling down for the recent many decades. Reliability issues with RF circuits have become more and more severe with device scaling down: reliability effects such as gate oxide break down, hot carrier injection, negative bias temperature instability, have been amplified as the device size shrinks. Process variability issues also become more predominant as the feature size decreases. With these insights provided, reliability and variability evaluations on typical RF circuits and possible compensation techniques are highly desirable.In this work, a class E power amplifier is designed and laid out using TSMC 0.18 (&)#181;m RF technology and the chip was fabricated. Oxide stress and hot electron tests were carried out at elevated supply voltage, fresh measurement results were compared with different stress conditions after 10 hours. Test results matched very well with mixed mode circuit simulations, proved that hot carrier effects degrades PA performances like output power, power efficiency, etc. Self- heating effects were examined on a class AB power amplifier since PA has high power operations. Device temperature simulation was done both in DC and mixed mode level. Different gate biasing techniques were analyzed and their abilities to compensate output power were compared. A simple gate biasing circuit turned out to be efficient to compensate self-heating effects under different localized heating situations. Process variation was studied on a classic Colpitts oscillator using Monte-Carlo simulation. Phase noise was examined since it is a key parameter in oscillator. Phase noise was modeled using analytical equations and supported by good match between MATLAB results and ADS simulation. An adaptive body biasing circuit was proposed to eliminate process variation. Results from probability density function simulation demonstrated its capability to relieve process variation on phase noise. Standard deviation of phase noise with adaptive body bias is much less than the one without compensation. Finally, a robust, adaptive design technique using PLL as on-chip sensor to reduce Process, Voltage, Temperature (P.V.T.) variations and other aging effects on RF PA was evaluated. The frequency and phase of ring oscillator need to be adjusted to follow the frequency and phase of input in PLL no matter how the working condition varies. As a result, the control signal of ring oscillator has to fluctuate according to the working condition, reflecting the P.V.T changes. RF circuits suffer from similar P.V.T. variations. The control signal of PLL is introduced to RF circuits and converted to the adaptive tuning voltage for substrate bias. Simulation results illustrate that the PA output power under different variations is more flat than the one with no compensation. Analytical equations show good support to what has been observed.
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Date Issued: 2013
Identifier: CFE0004664, ucf:49894
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004664

Title: Multi-Physics Model of Key Components In High Efficiency Vehicle Drive.
Creator: Lin, Shao Hua, Wu, Xinzhang, Sundaram, Kalpathy, Wahid, Parveen, Wei, Lei, Chow, Louis, University of Central Florida
Abstract / Description: 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: 2013
Identifier: CFE0005024, ucf:50016
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005024

Title: High Performance Low Voltage Power MOSFET for High-Frequency Synchronous Buck Converters.
Creator: Yang, Boyi, Shen, Zheng, Yuan, Jiann-Shiun, Sundaram, Kalpathy, Wu, Xinzhang, Xu, Shuming, University of Central Florida
Abstract / Description: Power management solutions such as voltage regulator (VR) mandate DC-DC converters with high power density, high switching frequency and high efficiency to meet the needs of future computers and telecom equipment. The trend towards DC-DC converters with higher switching frequency presents significant challenges to power MOSFET technology. Optimization of the MOSFETs plays an important role in improving low-voltage DC-DC converter performance. This dissertation focuses on developing and...
Show morePower management solutions such as voltage regulator (VR) mandate DC-DC converters with high power density, high switching frequency and high efficiency to meet the needs of future computers and telecom equipment. The trend towards DC-DC converters with higher switching frequency presents significant challenges to power MOSFET technology. Optimization of the MOSFETs plays an important role in improving low-voltage DC-DC converter performance. This dissertation focuses on developing and optimizing high performance low voltage power MOSFETs for high frequency applications.With an inherently large gate charge, the trench MOSFET suffers significant switching power losses and cannot continue to provide sufficient performance in high frequency applications. Moreover, the influence of parasitic impedance introduced by device packaging and PCB assembly in board level power supply designs becomes more pronounced as the output voltage continues to decrease and the nominal current continues to increase. This eventually raises the need for highly integrated solutions such as power supply in package (PSiP) or on chip (PSoC). However, it is often more desirable in some PSiP architectures to reverse the source/drain electrodes from electrical and/or thermal point of view. In this dissertation, a stacked-die Power Block PSiP architecture is first introduced to enable DC-DC buck converters with a current rating up to 40 A and a switching frequency in the MHz range. New high- and low-side NexFETs are specially designed and optimized for the new PSiP architecture to maximize its efficiency and power density. In particular, a new NexFET structure with its source electrode on the bottom side of the die (source-down) is designed to enable the innovative stacked-die PSiP technology with significantly reduced parasitic inductance and package footprint.It is also observed that in synchronous buck converter very fast switching of power MOSFETs sometimes leads to high voltage oscillations at the phase node of the buck converter, which may introduce additional power loss and cause EMI related problems and undesirable electrical stress to the power MOSFET. At the same time, the synchronous MOSFET plays an important role in determining the performance of the synchronous buck converter. The reverse recovery of its body diode and the Cdv/dt induced false trigger-on are two major mechanisms that impact the performance of the SyncFET. This dissertation introduces a new approach to effectively overcome the aforementioned challenges associated with the state-of-art technology. The threshold voltage of the low-side NexFET is intentionally reduced to minimize the conduction and body diode related power losses. Meanwhile, a monolithically integrated gate voltage pull-down circuitry is proposed to overcome the possible Cdv/dt induced turn-on issue inadvertently induced by the low VTH SynFET.Through extensive modeling and simulation, all these innovative concepts are integrated together in a power module and fabricated with a 0.35(&)#181;m process. With all these novel device technology improvements, the new power module delivers a significant improvement in efficiency and offers an excellent solution for future high frequency, high current density DC-DC converters. Megahertz operation of a Power Block incorporating these new device techniques is demonstrated with an excellent efficiency observed.
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Date Issued: 2012
Identifier: CFE0004642, ucf:49885
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004642

Title: Enhanced Microwave Hyperthermia using Nanoparticles.
Creator: Urdaneta, Maryory, Wahid, Parveen, Sundaram, Kalpathy, Richie, Samuel, Gong, Xun, Challapalli, Suryanarayana, University of Central Florida
Abstract / Description: In this dissertation a study of enhanced hyperthermia for cancer treatment through the use of magnetic nanoparticles is presented. Hyperthermia has been in use for many years, as a potential alternative method in cancer treatment, and high frequency microwave radiation has been used successfully to raise the tumor temperature to around 42(&)deg;C in superficial tumors without causing damage to surrounding healthy tissues. Magnetic fluid hyperthermia involves the use of magnetic nanoparticles...
Show moreIn this dissertation a study of enhanced hyperthermia for cancer treatment through the use of magnetic nanoparticles is presented. Hyperthermia has been in use for many years, as a potential alternative method in cancer treatment, and high frequency microwave radiation has been used successfully to raise the tumor temperature to around 42(&)deg;C in superficial tumors without causing damage to surrounding healthy tissues. Magnetic fluid hyperthermia involves the use of magnetic nanoparticles injected into the tumor before exposure to microwave radiation. The magnetic energy in the nanoparticles is converted into heat allowing for a more rapid rise of temperature in the tumor to the desired level. In addition, the nanoparticles allow the electromagnetic absorption to be focused in the tumor and can be used to treat deep tumors in organs, such as the liver. Iron oxide magnetic nanoparticles were considered for this study as they are non-toxic and bio-compatible. For the case of breast cancer, the values for the temperature and specific absorption rate (SAR) in the tumor and in the healthy tissue were obtained through simulations and validated by measurement done on phantom models. Various characteristics of the nanoparticles such as radius, magnetic susceptibility and concentration were considered. In order to take the effect of the blood flow, which causes cooling and helps maintain the body temperature, various blood perfusion rates for a tumor in the liver were studied. A human male model in SEMCAD X, in which blood flow can be adjusted, was used for simulations. The tumor was injected with the nanoparticles and the change in temperature upon exposure to electromagnetic radiation was observed. The simulated results were compared with measured results on a liver phantom model in which saline solution was used to model blood flow. There was good agreement between the measured and simulated results.
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Date Issued: 2015
Identifier: CFE0005731, ucf:50093
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005731

Title: Polymer Optical Fibers for Luminescent Solar Concentration.
Creator: Banaei, Seyed Esmaeil, Fathpour, Sasan, Gong, Xun, Sundaram, Kalpathy, Malocha, Donald, Abouraddy, Ayman, University of Central Florida
Abstract / Description: Luminescent solar concentrators (LSC's) are promising candidates for reducing the cost of solar power generation. Conventional LSC's are slab waveguides coated or doped with luminescence materials for absorption and guiding of light to the slab edges in order to convert optical energy into electricity via attached photovoltaic (PV) cells. Exploiting the advantages of optical fiber production, a fiber LSC (FLSC) is presented in this thesis, in which the waveguide is a polymeric optical fiber....
Show moreLuminescent solar concentrators (LSC's) are promising candidates for reducing the cost of solar power generation. Conventional LSC's are slab waveguides coated or doped with luminescence materials for absorption and guiding of light to the slab edges in order to convert optical energy into electricity via attached photovoltaic (PV) cells. Exploiting the advantages of optical fiber production, a fiber LSC (FLSC) is presented in this thesis, in which the waveguide is a polymeric optical fiber. A hybrid fiber structure is proposed for an efficient two-stage concentration of incident light, first into a small doped core using a cylindrical micro-lens that extends along the fiber, and second to the fiber ends by guiding the fluoresced light from the active dopants. Flexible sheets are assembled with fibers that can be bundled and attached to small-area PV cells. Small dimensions and directional guiding of the fibers allow for approximately one order of magnitude geometrical gain improvement over that of existing flat LSC's. In addition, the undesired limit of LSC size is eliminated in one direction.Modeling and optimization of an FLSC design is presented using polarization-ray tracing under realistic conditions with solar spectrum radiation and broad-band absorption and emission spectra of fluorescence materials with their inevitable self-absorption effect.Methods and results of fabrication and accurate optical characterization of such FLSC using two off-the-shelf organic dyes and a commercially available polymer, COP, are discussed in detail. Fiber preforms, fabricated under optimized conditions for low light transport loss, are thermally drawn into sub-millimeter-size fibers. Characterization of several samples with various concentrations of the two dyes shows an optical-to-optical conversion efficiency of 9.1% for a tandem combination of two 2.5-cm-long fibers with the efficiency gradually decreasing to 4.9% with increase in fiber length to 10 cm.
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Date Issued: 2013
Identifier: CFE0005083, ucf:50733
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005083

Title: Chemical Vapor Deposition Growth of Large Area 2D MoS2 Layers: Layer Orientation Control, Heterostructure Integration, And Applications for Stretchable Sensors.
Creator: Islam, Md. Ashraful, Jung, YeonWoong, Sundaram, Kalpathy, Yuan, Jiann-Shiun, Roy, Tania, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: Two-dimensional (2D)-layered MoS2 layers have exhibited a broad set of unusual and superior material properties unattainable in any traditional bulk materials, drawing significant research interests nowadays. For instance, they present excellent semiconducting properties accompanying high carrier mobility and large current ON/OFF ratio as well as extensive in-plane strain limit and thickness, projecting high suitably for emerging flexible and stretchable electronics. Such properties and...
Show moreTwo-dimensional (2D)-layered MoS2 layers have exhibited a broad set of unusual and superior material properties unattainable in any traditional bulk materials, drawing significant research interests nowadays. For instance, they present excellent semiconducting properties accompanying high carrier mobility and large current ON/OFF ratio as well as extensive in-plane strain limit and thickness, projecting high suitably for emerging flexible and stretchable electronics. Such properties and applications strongly depend on the physical orientation and chemical composition of constituent 2D layers. 2D MoS2 layers chemically grown in two distinct orientations, e.g., horizontal alignment for electronics and optoelectronics, and vertical alignment for electrochemical and sensing applications. Moreover, 2D heterostructure layers composed of vertically stacked dissimilar 2D TMDs held via weak van der Waals (vdW) attractions offer unique 2D/2D interfaces, envisioned to display exotic material properties, unattainable in their monocomponent counterparts. However, the underlying principle of their layer orientation-controlled growth and integrations are not well suited for scalable production, leaving their projected technological opportunities far from being realized for various novel applications. Herein, I study various aspects of 2D MoS2 layers that were studied from their large-area layer-orientation controlled growth and heterostructures integration to applications in stretchable electronic devices. I developed a chemical vapor deposition (CVD) synthesis, which can grow large-area ((>) cm2) 2D MoS2 layers in a layer-controlled manner and investigated their underlying growth mechanism. I then developed a viable transfer approach of the as-grown 2D layers and integrated them into secondary target substrates to realize a new type of 2D MoS2-layers based heterostructures. To further extend their layer-controlled CVD growth and integration approach, a high-performance stretchable 2D MoS2-based electrical sensors were demonstrated on the elastomeric substrates with unconventional structural layouts. This study paves the way to explore this emerging atomically-thin material in realizing a wide range of unusual device and technologies which have been foreseen to be impossible otherwise.
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Date Issued: 2019
Identifier: CFE0007820, ucf:52812
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007820

Title: Study of Novel Power Semiconductor Devices for Performance and Reliability.
Creator: Padmanabhan, Karthik, Yuan, Jiann-Shiun, Sundaram, Kalpathy, Atia, George, DeMara, Ronald, Chow, Lee, University of Central Florida
Abstract / Description: Power Semiconductor Devices are crucial components in present day power electronic systems. The performance and efficiency of the devices have a direct correlation with the power system efficiency. This dissertation will examine some of the components that are commonly used in a power system, with emphasis on their performance characteristics and reliability. In recent times, there has a proliferation of charge balance devices in high voltage discrete power devices. We examine the same charge...
Show morePower Semiconductor Devices are crucial components in present day power electronic systems. The performance and efficiency of the devices have a direct correlation with the power system efficiency. This dissertation will examine some of the components that are commonly used in a power system, with emphasis on their performance characteristics and reliability. In recent times, there has a proliferation of charge balance devices in high voltage discrete power devices. We examine the same charge balance concept in a fast recovery diode and a MOSFET. This is crucial in the extending system performance at compact dimensions. At smaller device and system sizes, the performance trade-off between the ON and OFF states becomes all the more critical. The focus on reducing the switching losses while maintaining system reliability increases. In a conventional planar technology, the technology places a limit on the switching performance owing to the larger die sizes. Using a charge balance structure helps achieve the improved trade-off, while working towards ultimately improving system reliability, size and cost.Chapter 1 introduces the basic power system based on an inductive switching circuit, and the various components that determine its efficiency. Chapter 2 presents a novel Trench Fast Recovery Diode (FRD) structure with injection control is proposed in this dissertation. The proposed structure achieves improved carrier profile without the need for excess lifetime control. This substantially improves the device performance, especially at extreme temperatures (-40oC to 175oC). The device maintains low leakage at high temperatures, and it's Qrr and Irm do not degrade as is the usual case in heavily electron radiated devices. A 1600 diode using this structure has been developed, with a low forward turn-on voltage and good reverse recovery properties. The experimental results show that the structure maintains its performance at high temperatures.In chapter 3, we develop a termination scheme for the previously mentioned diode. A major limitation on the performance of high voltage power semiconductor is the edge termination of the device. It is critical to maintain the breakdown voltage of the device without compromising the reliability of the device by controlling the surface electric field. A good termination structure is critical to the reliability of the power semiconductor device. The proposed termination uses a novel trench MOS with buried guard ring structure to completely eliminate high surface electric field in the silicon region of the termination. The termination scheme was applied towards a 1350 V fast recovery diode, and showed excellent results. It achieved 98% of parallel plane breakdown voltage, with low leakage and no shifts after High Temperature Reverse Bias testing due to mobile ion contamination from packaging mold compound.In chapter 4, we also investigate the device physics behind a superjunction MOSFET structure for improved robustness. The biggest issue with a completely charge balanced MOSFET is decreased robustness in an Unclamped Inductive Switching (UIS) Circuit. The equally charged P and N pillars result in a flat electric field profile, with the peak carrier density closer to the P-N junction at the surface. This results in an almost negligible positive dynamic Rds-on effect in the MOSFET. By changing the charge profile of the P-column, either by increasing it completely or by implementing a graded profile with the heavier P on top, we can change the field profile and shift the carrier density deeper into silicon, increasing the positive dynamic Rds-on effect. Simulation and experimental results are presented to support the theory and understanding.Chapter 5 summarizes all the theories presented and the contributions made by them in the field. It also seeks to highlight future work to be done in these areas.
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Date Issued: 2016
Identifier: CFE0006158, ucf:51148
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006158

Title: Uncooled Infrared Detector Featuring Silicon based Nanoscale Thermocouple.
Creator: Modarres-Zadeh, Mohammad, Abdolvand, Reza, Sundaram, Kalpathy, Yuan, Jiann-Shiun, Malocha, Donald, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: The main focus of this dissertation is to improve the performance of thermoelectric (TE)infrared (IR) detectors. TE IR detectors are part of uncooled detectors that can operate at roomtemperature. These detectors have been around for many years, however, their performance hasbeen lower than their contesting technologies. A novel high-responsivity uncooled thermoelectricinfrared detector is designed, fabricated, and characterized. This detector features a single standalonepolysilicon-based...
Show moreThe main focus of this dissertation is to improve the performance of thermoelectric (TE)infrared (IR) detectors. TE IR detectors are part of uncooled detectors that can operate at roomtemperature. These detectors have been around for many years, however, their performance hasbeen lower than their contesting technologies. A novel high-responsivity uncooled thermoelectricinfrared detector is designed, fabricated, and characterized. This detector features a single standalonepolysilicon-based thermocouple (without a supporting membrane) covered by an umbrellalikeoptical-cavity IR absorber. It is proved that the highest responsivity in the developed detectorscan be achieved with only one thermocouple. Since the sub-micrometer polysilicon TE wires arethe only heat path from the hot junction to the substrate, a superior thermal isolation is achieved.A responsivity of 1800 V/W and a detectivity of 2 ? 10^8 (cm. sqrt(Hz)W^?1) are measured from a20?m x 20?m detector comparable to the performance of detectors used in commercial focalplanar arrays. This performance in a compact and manufacturable design elevates the position ofthermoelectric IR sensors as a candidate for low-power, high performance, and inexpensive focalplanar arrays. The improvement in performance is mostly due to low thermal conductivity of thinpolysilicon wires. A feature is designed and fabricated to characterize the thermal conductivity ofsuch a wire and it is shown for the first time that the thermal conductivity of thin polysilicon filmscan be much lower than that of the bulk. Thermal conductivity of ~110nm LPCVD polysilicondeposited at 620C is measured to be ~3.5W/m.K.
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Date Issued: 2016
Identifier: CFE0006537, ucf:51321
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006537

ESD (3)	+ -
MOSFET (3)	+ -
XPS (3)	+ -
2D materials (2)	+ -
BST (2)	+ -

Cryogenic (2)	+ -
Electrostatic Discharge (2)	+ -
LDMOS (2)	+ -
MEMS (2)	+ -
Optimization (2)	+ -
PMSM (2)	+ -
Piezoelectric (2)	+ -
Power MOSFET (2)	+ -
Power Semiconductor (2)	+ -
RF (2)	+ -
Reliability (2)	+ -
Resonator (2)	+ -
Sputtering (2)	+ -
Superjunction (2)	+ -
TCAD (2)	+ -
Temperature (2)	+ -
Thin Films (2)	+ -
electromagnetic compatibility (2)	+ -
low-k materials (2)	+ -
metrology (2)	+ -
photovoltaic (2)	+ -
power amplifier (2)	+ -
thin film (2)	+ -
03/30/2018 (1)	+ -
ASCII (1)	+ -

University of Central Florida (73)	+ -
Sundaram, Kalpathy (71)	+ -
Yuan, Jiann-Shiun (25)	+ -
Abdolvand, Reza (10)	+ -
Gong, Xun (9)	+ -

Kapoor, Vikram (9)	+ -
Fan, Deliang (7)	+ -
Wei, Lei (7)	+ -
Jin, Yier (6)	+ -
Wahid, Parveen (6)	+ -
Chow, Lee (5)	+ -
Chow, Louis (5)	+ -
Malocha, Donald (5)	+ -
Salcedo, Javier (5)	+ -
Wu, Xinzhang (5)	+ -
Batarseh, Issa (4)	+ -
DeMara, Ronald (4)	+ -
Kar, Aravinda (4)	+ -
Schoenfeld, Winston (4)	+ -
Shen, Zheng (4)	+ -
Cho, Hyoung Jin (3)	+ -
Coffey, Kevin (3)	+ -
Fathpour, Sasan (3)	+ -
Lin, Mingjie (3)	+ -
Richie, Samuel (3)	+ -
Roy, Tania (3)	+ -
Atia, George (2)	+ -
Davis, Kristopher (2)	+ -
Heinrich, Helge (2)	+ -
Jha, Sumit Kumar (2)	+ -

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