Current Search: Powers (x)
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Title
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DESIGN AND MODELING OF RADIATION HARDENED LATERAL POWER MOSFETS.
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Creator
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Landowski, Matthew, Shen, Zheng, University of Central Florida
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Abstract / Description
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Galactic-cosmic-rays (GCR) exist in space from unknown origins. A cosmic ray is a very high energy electron, proton, or heavy ion. As a GCR transverses a power semiconductor device, electron-hole-pairs (ehps) are generated along the ion track. Effects from this are referred to as single-event-effects (SEEs). A subset of a SEE is single-event burnout (SEB) which occurs when the parasitic bipolar junction transistor is triggered leading to thermal runaway. The failure mechanism is a complicated...
Show moreGalactic-cosmic-rays (GCR) exist in space from unknown origins. A cosmic ray is a very high energy electron, proton, or heavy ion. As a GCR transverses a power semiconductor device, electron-hole-pairs (ehps) are generated along the ion track. Effects from this are referred to as single-event-effects (SEEs). A subset of a SEE is single-event burnout (SEB) which occurs when the parasitic bipolar junction transistor is triggered leading to thermal runaway. The failure mechanism is a complicated mix of photo-generated current, avalanche generated current, and activation of the inherent parasitic bipolar transistor. Current space-borne power systems lack the utility and advantages of terrestrial power systems. Vertical-double-diffused MOSFETs (VDMOS) is by far the most common power semiconductor device and are very susceptible to SEEs by their vertical structure. Modern space power switches typically require system designers to de-rate the power semiconductor switching device to account for this. Consequently, the power system suffers from increased size, cost, and decreased performance. Their switching speed is limited due to their vertical structure and cannot be used for MHz frequency applications limiting the use of modern digital electronics for space missions. Thus, the Power Semiconductor Research Laboratory at the University of Central Florida in conjunction with Sandia National Laboratories is developing a rad-hard by design lateral-double-diffused MOSFET (LDMOS). The study provides a novel in-depth physical analysis of the mechanisms that cause the LDMOS to burnout during an SEE and provides guidelines for making the LDMOS rad-hard to SEB. Total dose radiation, another important radiation effect, can cause threshold voltage shifts but is beyond the scope of this study. The devices presented have been fabricated with a known total dose radiation hard CMOS process. Single-event burnout data from simulations and experiments are presented in the study to prove the viability of using the LDMOS to replace the VDMOS for space power systems. The LDMOS is capable of higher switching speeds due to a reduced drain-gate feedback capacitance (Miller Capacitor). Since the device is lateral it is compatible with complimentary-metal-oxide-semiconductor (CMOS) processes, lowering developing time and fabrication costs. High switching frequencies permit the use of high density point-of-load conversion and provide a fast dynamic response.
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Date Issued
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2009
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Identifier
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CFE0002795, ucf:48113
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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/CFE0002795
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Title
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A REALIST INTERPRETATION OF U.S.RELATIONS WITH CHINA.
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Creator
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Zhang, Xiansheng, Morales, Waltraud, University of Central Florida
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Abstract / Description
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Realism theory provides the most powerful explanation for the state of war and the rise and fall of great powers. It expounds the important concepts and themes like national sovereignty, security, survival, interests, balance of power, balance of terror, alliance, dominance, hegemony and polarity. Realism can be classified as classical realism, structural realism and neoclassical realism. In recent years, liberalism, globalism and constructivism also have greatly influenced academics and...
Show moreRealism theory provides the most powerful explanation for the state of war and the rise and fall of great powers. It expounds the important concepts and themes like national sovereignty, security, survival, interests, balance of power, balance of terror, alliance, dominance, hegemony and polarity. Realism can be classified as classical realism, structural realism and neoclassical realism. In recent years, liberalism, globalism and constructivism also have greatly influenced academics and policy-makers under the new phenomena of globalization and terrorism. This paper explores how classical realism theory has been applied to and revealed in the issue of American policy towards China. The past years of U.S. relations with China have been marked by many wars and diplomatic issues that bear important messages for contemporary policy-makers. Based upon the most representative incidents in the chronicles, this paper categorizes American relations with China into three periods: period one, from commercialism in 1784 to imperialism in 1899; period two, from dominance in 1900 to confrontation in 1949; Period three, from enemies in 1950 to competitors in 2009. From a brief retrospective of major events that occurred, it is concluded that most incidents are related to national interest and power issues, while only several cases are about ideological disputes. The emergence of China as an economic power within the last few years will shape the world as much as the United States in the late 19th century. As America is the worldÃÂ's greatest power and China is the worldÃÂ's greatest emerging power, the relationship between these two countries will largely determine the history of the twenty-first century. History teaches that such power transitions are inherently fraught with dangers and opportunities. Thus, it would serve the interests of the United States to rethink its relationship with China and make its policies more global and focused on the long term. No matter what happens in China, American policy towards that country should be guided by a clear and firm sense of American national interests.
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Date Issued
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2010
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Identifier
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CFE0003072, ucf:48308
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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/CFE0003072
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Title
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Florida macrolichens as potential bioindicators of environmental quality : a baseline study.
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Creator
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Neal, Harry V., Wanielista, Martin P., Arts and Sciences
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Abstract / Description
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University of Central Florida College of Arts and Sciences Thesis; Lichens have been used extensively and with considerable success as bioindicators of atmospheric pollution in North America and Europe for more than thirty years. Little research has followed in tropical and subtropical regions where population growth is rapid and environmental pressures unprecedented. However, taxa used as bioindicators in other studies and/or taxa having this potential, occur naturally in Central Florida. A...
Show moreUniversity of Central Florida College of Arts and Sciences Thesis; Lichens have been used extensively and with considerable success as bioindicators of atmospheric pollution in North America and Europe for more than thirty years. Little research has followed in tropical and subtropical regions where population growth is rapid and environmental pressures unprecedented. However, taxa used as bioindicators in other studies and/or taxa having this potential, occur naturally in Central Florida. A new potential major source of pollution, the coal-fired Curtis H. Stanton Energy Canter, is about to begin operation providing the opportunity to determine the extent of impact. Therefore, lichen monitoring sites have been established and the collection of baseline data reflecting species diversity, frequency, overall cover and vitality has been accomplished. Theme locations will be preserved for future monitoring activities. Voucher specimens and photographic documentation of sample populations have been deposited in the herbarium of the University of Central Florida.
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Date Issued
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1986
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Identifier
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CFR0004338, ucf:52996
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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/CFR0004338
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Title
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NEUROERGONOMICS STUDY: ANALYSIS OF BRAIN EEG's ACTIVITY DURING MANUAL LIFTING TASKS.
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Creator
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Aljuaid, Awad, Xanthopoulos, Petros, Karwowski, Waldemar, Hancock, Peter, McCauley, Pamela, Lee, Gene, Kincaid, John, University of Central Florida
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Abstract / Description
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Electroencephalography (EEG) has been shown to be a reliable tool in neuroergonomics studies due to the relatively low cost of brain data collection and limited body invasion. The application of EEG frequency bands (including theta, alpha and beta), enjoyed a wide range of interest in physical and cognitive ergonomics. The psychophysical approach has been used for decades to improve safe work practices by understanding human limitations in manual materials handling. The main objective of this...
Show moreElectroencephalography (EEG) has been shown to be a reliable tool in neuroergonomics studies due to the relatively low cost of brain data collection and limited body invasion. The application of EEG frequency bands (including theta, alpha and beta), enjoyed a wide range of interest in physical and cognitive ergonomics. The psychophysical approach has been used for decades to improve safe work practices by understanding human limitations in manual materials handling. The main objective of this research project was to study the brain's EEG activity expressed by the power spectral density during manual lifting tasks related to: 1) the maximum acceptable weight of lift (MAWL) and 2) isokinetic and isometric lifting strength tests measurement outcomes. The first study investigated the changes in EEG power spectral density during determination of MAWL under low, medium, and high lifting frequencies. A high-density wireless dry cell EEG device has been used to record EEG signals. Twenty healthy males participated in this study. Subjects repeated the same experiment after two weeks. Analysis of variance (ANOVA) showed significant differences in EEG power spectral density between different lifting frequencies at three main brain areas (frontal, central, and parietal). The second study revealed differences in brain activities during isokinetic and isometric strength measurements, based on the recording and analysis of EEG power spectral density. This research project is the first study of EEG activity during manual lifting tasks, including the assessment of MAWL by the psychophysical method, as well as the measurement of human isokinetic and isometric strengths. The results of this project are considered critical to our increased understanding of the neural correlates of human physical activities, and consequently should have a positive impact on workplace design that considers brain activity related to specific human capabilities and limitations in manual lifting tasks.
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Date Issued
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2016
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Identifier
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CFE0006067, ucf:50996
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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/CFE0006067
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Title
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Computational Fluid Dynamics Proof of Concept and Analysis of a Self-Powered Fontan Circulation.
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Creator
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Ni, Marcus, Kassab, Alain, Divo, Eduardo, Chopra, Manoj, University of Central Florida
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Abstract / Description
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The Fontan circulation is a result of the last (third stage) surgical procedure to correct a single ventricle congenital cardiac disorder in children. Although the Fontan circulation has been successfully established in surgeries over the years, it is flawed and can lead in certain cases to pre-mature death. The main cause of this failure is due to increased pulmonary vascular resistance due to loss pulse pressure and blood flow. In healthy circulations, the heart pumps directly to the lungs,...
Show moreThe Fontan circulation is a result of the last (third stage) surgical procedure to correct a single ventricle congenital cardiac disorder in children. Although the Fontan circulation has been successfully established in surgeries over the years, it is flawed and can lead in certain cases to pre-mature death. The main cause of this failure is due to increased pulmonary vascular resistance due to loss pulse pressure and blood flow. In healthy circulations, the heart pumps directly to the lungs, where as (")Single Ventricle(") patients must use a single sided heart to supply blood to the rest of the body before the lungs. Improvements to the Fontan circulation have been proposed, but they require extensive care or external devices. We propose a (")Self-Powered(") Fontan circulation that will inject energy into the pulmonary system by adding an injection jet shunt (IJS) directly from the heart. The IJS will provide the pulse pressure, blood flow, and entrainment that the pulmonary vascular system needs to function at a healthy level. The difference between a healthy and sick Fontan circulation is 3-5[mmHg] in the IVC. The goal of the IJS is to cause this 3-5[mmHg] pressure drop in the IVC. In the analysis of the Fontan, ascertaining energy losses due to flow jet impingements and flow mixing is critical. Moreover, in order to better understand surgical alternatives is it important to have a robust multi-scale 0D-3D CFD analysis tool that permits investigation of surgical alternatives in a virtual physics-based environment. To this end, a lumped parameter model (LPM) is tightly coupled at the time step level with a full 3D computational fluid dynamics (CFD) model. Using this model scheme, the Fontan test section is no longer being modeled by the LPM. Therefore, it is not limited by the 0D nature of the vascular resistance, capacitance, and inertia bed model. The CFD can take over at the area of interest which accounts for flow directionality and momentum transfer that the LPM is unable to capture. To efficiently calculate optimal IJS configurations, a closed loop steady state model was created to solve a simplified Fontan circulation in 3D. Three models were created with several different optimized configurations, a synthetic model (average dimensions of 2-4 year-old Fontan patients), and two patient-specific models (10 and 24-year-old). The model configurations include changes in the IJS nozzle diameter and IJS placement along the pulmonary artery. These configurations are compared to a baseline model with no IJS. All three models suggest that the IJS helps to decrease IVC pressure while increasing pulse pressure and blood flow to the pulmonary system.
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Date Issued
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2017
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Identifier
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CFE0006630, ucf:51303
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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/CFE0006630
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Title
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Three Essays on Market Efficiency and Corporate Diversification.
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Creator
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Jaber Hyder, Fawzi, Chen, Honghui, Gatchev, Vladimir, Frye, Melissa, Choi, Yoon, Schnitzlein, Charles, University of Central Florida
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Abstract / Description
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In my first essay, I use additions to the S(&)P 500 index as a laboratory to investigate how the interaction between arbitrageurs and arbitrage risk affects security prices. I find that the price effect is strong when there is high arbitrage risk (as measured by the lack of close substitutes) and low presence of arbitrageurs (as measured by low ownership by active institutions). Furthermore, a strong presence of arbitrageurs moderates the effect of arbitrage risk on the post-addition price...
Show moreIn my first essay, I use additions to the S(&)P 500 index as a laboratory to investigate how the interaction between arbitrageurs and arbitrage risk affects security prices. I find that the price effect is strong when there is high arbitrage risk (as measured by the lack of close substitutes) and low presence of arbitrageurs (as measured by low ownership by active institutions). Furthermore, a strong presence of arbitrageurs moderates the effect of arbitrage risk on the post-addition price reaction of added stocks. I also find a significant decrease in arbitrageurs' ownership in the added stocks post addition. More importantly, this decrease is accompanied by a significant increase in arbitrageurs' ownership in the added stocks' close substitutes. My second essay examines the sensitivity of investments to changes in investment opportunities for diversified and for single-segment firms. Because many concerns have been raised about existing proxies of investment opportunities, I introduce and examine the empirical performance of a new proxy based on financial analysts' earnings forecasts. The findings are consistent with the idea that firms respond efficiently to changes in investment opportunities. I find that firms increase (decrease) their capital expenditures when there is a favorable (unfavorable) change in opportunities. In addition, I find that diversified firms are more sensitive to changes in investment opportunities than are single-segment firms and that much of the difference in investment behavior between the two types of firms is explained by changes in investment opportunities. My findings are consistent with the idea that, when compared to single-segment firms, diversified firms use their larger internal capital markets and enjoy a less constrained response to changes in investment opportunities. The overall findings are in contrast to existing evidence that diversified firms allocate resources inefficiently.In my third essay, I investigate how the diversification discount depends on internal and external governance control mechanisms. The study uses CEO power to measure internal control and institutional ownership to measure external control. I find that CEO power has a negative effect on firm value and that this effect is greater for diversified firms. I also find that while institutional ownership is positively related to the value of single-segment firms it is not significantly related to the value of multi-segment firms. The overall findings that the diversification discount is more pronounced for firms with weaker internal and external governance control mechanisms support the hypothesis that governance control mechanisms are less effective in diversified firms than in single-segment firms.
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Date Issued
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2017
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Identifier
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CFE0006606, ucf:51265
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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/CFE0006606
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Title
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Control Based Soft Switching Three-phase Micro-inverter: Efficiency and Power Density Optimization.
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Creator
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Amirahmadi, Ahmadreza, Batarseh, Issa, Lotfifard, Saeed, Mikhael, Wasfy, Wu, Xinzhang, Kutkut, Nasser, University of Central Florida
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Abstract / Description
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In the field of renewable energy, solar photovoltaic is growing exponentially. Grid-tied PV micro-inverters have become the trend for future PV system development because of their remarkable advantages such as enhanced energy production due to MPPT implementation for each PV panel, high reliability due to redundant and distributed system architecture, and simple design, installation, and management due to its plug-and-play feature. Conventional approaches for the PV micro-inverters are mainly...
Show moreIn the field of renewable energy, solar photovoltaic is growing exponentially. Grid-tied PV micro-inverters have become the trend for future PV system development because of their remarkable advantages such as enhanced energy production due to MPPT implementation for each PV panel, high reliability due to redundant and distributed system architecture, and simple design, installation, and management due to its plug-and-play feature. Conventional approaches for the PV micro-inverters are mainly in the form of single-phase grid connected and they aim at the residential and commercial rooftop applications. It would be advantageous to extend the micro-inverter concept to large size PV installations such as MW-class solar farms where three-phase AC connections are used.The relatively high cost of the three-phase micro-inverter is the biggest barrier to its large scale deployment. Increasing the switching frequency may be the best way to reduce cost by shrinking the size of reactive components and heat-sink. However, this approach could cause conversion efficiency to drop dramatically without employing soft switching techniques or using costly new devices.This dissertation presents a new zero voltage switching control method that is suitable for low power applications such as three-phase micro-inverters. The proposed hybrid boundary conduction mode (BCM) current control method increases the efficiency and power density of the micro-inverters and features both reduced number of components and easy digital implementation. Zero voltage switching is achieved by controlling the inductor current bi-directional in every switching cycle and results in lower switching losses, higher operating frequency, and reduced size and cost of passive components, especially magnetic cores. Some practical aspects of hybrid control implementation such as dead-time insertion can degrade the performance of the micro-inverter. A dead-time compensation method that improves the performance of hybrid BCM current control by decreasing the output current THD and reducing the zero crossing distortion is presented.Different BCM ZVS current control modulation schemes are compared based on power losses breakdown, switching frequency range, and current quality. Compared to continuous conduction mode (CCM) current control, BCM ZVS control decreases MOSFET switching losses and filter inductor conduction losses but increases MOSFET conduction losses and inductor core losses. Based on the loss analysis, a dual-mode current modulation method combining ZVS and zero current switching (ZCS) schemes is proposed to improve the efficiency of the micro-inverter.Finally, a method of maintaining high power conversion efficiency across the entire load range of the three-phase micro-inverter is proposed. The proposed control method substantially increases the conversion efficiency at light loads by minimizing switching losses of semiconductor devices as well as core losses of magnetic components. This is accomplished by entering a phase skipping operating mode wherein two phases of an inverter are disabled and three inverters are combined to form a new three-phase system with minimal grid imbalance. A 400W prototype of a three-phase micro-inverter and its hybrid control system have been designed and tested under different conditions to verify the effectiveness of the proposed controller, current modulation scheme, and light load efficiency enhancement method.
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Date Issued
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2014
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Identifier
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CFE0005125, ucf:50703
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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/CFE0005125
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Title
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Modeling and Solving Large-scale Stochastic Mixed-Integer Problems in Transportation and Power Systems.
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Creator
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Huang, Zhouchun, Zheng, Qipeng, Xanthopoulos, Petros, Pazour, Jennifer, Chang, Ni-bin, University of Central Florida
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Abstract / Description
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In this dissertation, various optimization problems from the area of transportation and power systems will be respectively investigated and the uncertainty will be considered in each problem. Specifically, a long-term problem of electricity infrastructure investment is studied to address the planning for capacity expansion in electrical power systems with the integration of short-term operations. The future investment costs and real-time customer demands cannot be perfectly forecasted and...
Show moreIn this dissertation, various optimization problems from the area of transportation and power systems will be respectively investigated and the uncertainty will be considered in each problem. Specifically, a long-term problem of electricity infrastructure investment is studied to address the planning for capacity expansion in electrical power systems with the integration of short-term operations. The future investment costs and real-time customer demands cannot be perfectly forecasted and thus are considered to be random. Another maintenance scheduling problem is studied for power systems, particularly for natural gas fueled power plants, taking into account gas contracting and the opportunity of purchasing and selling gas in the spot market as well as the maintenance scheduling considering the uncertainty of electricity and gas prices in the spot market. In addition, different vehicle routing problems are researched seeking the route for each vehicle so that the total traveling cost is minimized subject to the constraints and uncertain parameters in corresponding transportation systems.The investigation of each problem in this dissertation mainly consists of two parts, i.e., the formulation of its mathematical model and the development of solution algorithm for solving the model. The stochastic programming is applied as the framework to model each problem and address the uncertainty, while the approach of dealing with the randomness varies in terms of the relationships between the uncertain elements and objective functions or constraints. All the problems will be modeled as stochastic mixed-integer programs, and the huge numbers of involved decision variables and constraints make each problem large-scale and very difficult to manage. In this dissertation, efficient algorithms are developed for these problems in the context of advanced methodologies of optimization and operations research, such as branch and cut, benders decomposition, column generation and Lagrangian method. Computational experiments are implemented for each problem and the results will be present and discussed. The research carried out in this dissertation would be beneficial to both researchers and practitioners seeking to model and solve similar optimization problems in transportation and power systems when uncertainty is involved.
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Date Issued
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2016
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Identifier
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CFE0006328, ucf:51559
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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/CFE0006328
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Title
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DESIGNING LIGHT FILTERS TO DETECT SKIN USING A LOW-POWERED SENSOR.
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Creator
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Tariq, Muhammad, Wisniewski, Pamela, Gong, Boqing, Leavens, Gary, University of Central Florida
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Abstract / Description
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Detection of nudity in photos and videos, especially prior to uploading to the internet, is vital to solving many problems related to adolescent sexting, the distribution of child pornography, and cyber-bullying. The problem with using nudity detection algorithms as a means to combat these problems is that: 1) it implies that a digitized nude photo of a minor already exists (i.e., child pornography), and 2) there are real ethical and legal concerns around the distribution and processing of...
Show moreDetection of nudity in photos and videos, especially prior to uploading to the internet, is vital to solving many problems related to adolescent sexting, the distribution of child pornography, and cyber-bullying. The problem with using nudity detection algorithms as a means to combat these problems is that: 1) it implies that a digitized nude photo of a minor already exists (i.e., child pornography), and 2) there are real ethical and legal concerns around the distribution and processing of child pornography. Once a camera captures an image, that image is no longer secure. Therefore, we need to develop new privacy-preserving solutions that prevent the digital capture of nude imagery of minors. My research takes a first step in trying to accomplish this long-term goal: In this thesis, I examine the feasibility of using a low-powered sensor to detect skin dominance (defined as an image comprised of 50% or more of human skin tone) in a visual scene. By designing four custom light filters to enhance the digital information extracted from 300 scenes captured with the sensor (without digitizing high-fidelity visual features), I was able to accurately detect a skin dominant scene with 83.7% accuracy, 83% precision, and 85% recall. The long-term goal to be achieved in the future is to design a low-powered vision sensor that can be mounted on a digital camera lens on a teen's mobile device to detect and/or prevent the capture of nude imagery. Thus, I discuss the limitations of this work toward this larger goal, as well as future research directions.
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Date Issued
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2017
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Identifier
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CFE0006806, ucf:51792
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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/CFE0006806
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Title
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Effects of climate change and anthropogenic activities on the Everglades landscape.
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Creator
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Sandhu, Daljit, Singh, Arvind, Wang, Dingbao, Medeiros, Stephen, University of Central Florida
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Abstract / Description
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The Everglades has been experiencing major changes, both climatic and anthropogenic, such that the landscape is experiencing additional stresses and forcings leading it away from its natural equilibrium. The land within and surrounding the Everglades has undergone severe modifications that may have detrimental effects on wildlife and natural features, such as rivers and landscape connectivity. Here in this study, the main focus is on understanding and quantifying hydrologic and geomorphic...
Show moreThe Everglades has been experiencing major changes, both climatic and anthropogenic, such that the landscape is experiencing additional stresses and forcings leading it away from its natural equilibrium. The land within and surrounding the Everglades has undergone severe modifications that may have detrimental effects on wildlife and natural features, such as rivers and landscape connectivity. Here in this study, the main focus is on understanding and quantifying hydrologic and geomorphic signatures of climatic and anthropogenic changes on the Everglades landscape. For this, in particular, available data on natural hydrological processes was used, such as rainfall, groundwater elevation, streamflow as well as surface elevations and satellite images for three different regions. These regions are categorized as forested, urban (nearby Everglades regions) and transition (in between forested and urban regions). The results show distinct differences in the statistics of observed hydrologic variables for the three different regions. For example, the probability distribution functions (PDFs) of groundwater elevation for the case of urban region show a shift in mean as well as lower asymmetry as compared to forested regions. In addition, a significant difference in the slopes between smaller and larger scales of the power spectral densities (PSDs) is observed when transitioning from forested to urban. For the case of the streamflow PDFs and PSDs, the opposite trends are observed. Basin properties extracted from digital elevation models (DEMs) of the Everglades reveal that drainage densities increase when moving from the urban to the forested sub-regions, highlighting the topographic and land use/land cover changes that the Everglades has been subjected to in recent years. Finally, computing the interarrival times of extreme ((>)95th percentile) events that suggest power-law behavior, the changes in power-law exponents of the hydrologic processes further highlights how these processes differ spatially and how the landscape has to respond to these changes. Quantifying these observed changes will help develop a better understanding of the Everglades and other wetlands ecosystems for management to future changes and restoration.
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Date Issued
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2016
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Identifier
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CFE0006495, ucf:51395
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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/CFE0006495
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Title
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Investigating the Impact of Levels of Experience on Workload During Nuclear Power Plant Operations.
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Creator
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Harris, Jonathan, Reinerman, Lauren, Karwowski, Waldemar, Hancock, Peter, Barber, Daniel, University of Central Florida
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Abstract / Description
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The human-machine interface (HMI) of a Nuclear Power Plant (NPP) Main Control Room (MCR) is complex. Understanding HMI factors that influence Reactor Operator (RO) performance and workload when controlling an NPP is important. The Nuclear Regulatory Commission (NRC) began a program of research known as the Human Performance Test Facility (HPTF) with the goal of collecting human performance data to better understand cognitive and physical elements that support safe control room operation. The...
Show moreThe human-machine interface (HMI) of a Nuclear Power Plant (NPP) Main Control Room (MCR) is complex. Understanding HMI factors that influence Reactor Operator (RO) performance and workload when controlling an NPP is important. The Nuclear Regulatory Commission (NRC) began a program of research known as the Human Performance Test Facility (HPTF) with the goal of collecting human performance data to better understand cognitive and physical elements that support safe control room operation. The HPTF team developed an experimental methodology to evaluate workload using perceived ratings, performance measures, and physiological correlates. This methodology focuses on tasks commonly performed during operations in an NPP. These tasks include monitoring plant parameters, following defined procedures, and manipulating controls to change the state of the NPP. O'Hara and colleagues developed a framework for task classification. Reinerman-Jones and colleagues modified this framework such that monitoring and detection are separate task types. The task types (i.e., checking, detection, and response implementation) selected for experimentation are composed of steps within defined operating procedures that are rule-based. Testing workload using sufficient numbers of ROs is impractical due to limited availability. The HPTF has developed the (")equal but different(") principle. This principle attempts to simplify complex tasks, such that novices can perform them and experience equivalent workload trends as an expert would when performing the original task. The validity of using the (")equal but different(") principle with novices in place of experts is uncertain. This research addresses this uncertainty by comparing novices and experts using the (")equal but different(") principle. Novices performed four tasks within each of the three task types using a simplified Instrument and Control (I(&)C) panel and a reduced 3-way communication instruction set. Experts performed the same four tasks within each task type with a fully configured I(&)C panel and a complete 3-way instruction set. Overall, the experts across the three task types tended to rate level of perceived workload lower than novices. However, experts also rated themselves as performing worse for the three task types than novices. Experts performed better than novices when it came to identifying correct I(&)C; however, their 3-way communication performance was worse. Physiological measures from EEG between the two groups were not statistically different. ECG findings did show a slight difference.The methodology and associated findings has applicability for MCR designs and regulation recommendations. Novice populations are easier to access than experts and the present research shows that when properly designed, novices can serve in complex operator positions.
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Date Issued
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2017
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Identifier
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CFE0006946, ucf:51634
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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/CFE0006946
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Title
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An SoS Conceptual Model, LVC Simulation Framework, and a Prototypical Implementation of Unmanned System Interventions for Nuclear Power Plant Disaster Preparedness, Response, and Mitigation.
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Creator
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Davis, Matthew, Proctor, Michael, O'Neal, Thomas, Reilly, Charles, Sulfredge, C., Smith, Roger, University of Central Florida
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Abstract / Description
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Nuclear power plant disasters can have severe and far-reaching consequences, thus emergency managers and first responders from utility owners to the DoD must be prepared to respond to and mitigate effects protecting the public and environment from further damage. Rapidly emerging unmanned systems promise significant improvement in response and mitigation of nuclear disasters. Models and simulations (M(&)S) may play a significant role in improving readiness and reducing risks through its use...
Show moreNuclear power plant disasters can have severe and far-reaching consequences, thus emergency managers and first responders from utility owners to the DoD must be prepared to respond to and mitigate effects protecting the public and environment from further damage. Rapidly emerging unmanned systems promise significant improvement in response and mitigation of nuclear disasters. Models and simulations (M(&)S) may play a significant role in improving readiness and reducing risks through its use in planning, analysis, preparation training, and mitigation rehearsal for a wide spectrum of derivate scenarios. Legacy nuclear reactor M(&)S lack interoperability between themselves and avatar or agent-based simulations of emergent unmanned systems. Bridging the gap between past and the evolving future, we propose a conceptual model (CM) using a System of System (SoS) approach, a simulation federation framework capable of supporting concurrent and interoperating live, virtual and constructive simulation (LVC), and demonstrate a prototypical implementation of an unmanned system intervention for nuclear power plant disaster using the constructive simulation component. The SoS CM, LVC simulation framework, and prototypical implementation are generalizable to other preparedness, response, and mitigation scenarios. The SoS CM broadens the current stovepipe reactor-based simulations to a system-of-system perspective. The framework enables distributed interoperating simulations with a network of legacy and emergent avatar and agent simulations. The unmanned system implementation demonstrates feasibility of the SoS CM and LVC framework through replication of selective Fukushima events. Further, the system-of-systems approach advances life cycle stages including concept exploration, system design, engineering, training, and mission rehearsal. Live, virtual, and constructive component subsystems of the CM are described along with an explanation of input/output requirements. Finally, applications to analysis and training, an evaluation of the SoS CM based on recently proposed criteria found in the literature, and suggestions for future research are discussed.
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Date Issued
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2017
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Identifier
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CFE0006732, ucf:51879
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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/CFE0006732
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Title
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A Multiagent Q-learning-based Restoration Algorithm for Resilient Distribution System Operation.
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Creator
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Hong, Jungseok, Sun, Wei, Zhou, Qun, Zheng, Qipeng, University of Central Florida
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Abstract / Description
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Natural disasters, human errors, and technical issues have caused disastrous blackouts to power systems and resulted in enormous economic losses. Moreover, distributed energy resources have been integrated into distribution systems, which bring extra uncertainty and challenges to system restoration. Therefore, the restoration of power distribution systems requires more efficient and effective methods to provide resilient operation.In the literature, using Q-learning and multiagent system (MAS...
Show moreNatural disasters, human errors, and technical issues have caused disastrous blackouts to power systems and resulted in enormous economic losses. Moreover, distributed energy resources have been integrated into distribution systems, which bring extra uncertainty and challenges to system restoration. Therefore, the restoration of power distribution systems requires more efficient and effective methods to provide resilient operation.In the literature, using Q-learning and multiagent system (MAS) to restore power systems has the limitation in real system application, without considering power system operation constraints. In order to adapt to system condition changes quickly, a restoration algorithm using Q-learning and MAS, together with the combination method and battery algorithm is proposed in this study. The developed algorithm considers voltage and current constraints while finding system switching configuration to maximize the load pick-up after faults happen to the given system. The algorithm consists of three parts. First, it finds switching configurations using Q-learning. Second, the combination algorithm works as a back-up plan in case of the solution from Q-learning violates system constraints. Third, the battery algorithm is applied to determine the charging or discharging schedule of battery systems. The obtained switching configuration provides restoration solutions without violating system constraints. Furthermore, the algorithm can adjust switching configurations after the restoration. For example, when renewable output changes, the algorithm provides an adjusted solution to avoid violating system constraints.The proposed algorithm has been tested in the modified IEEE 9-bus system using the real-time digital simulator. Simulation results demonstrate that the algorithm offers an efficient and effective restoration strategy for resilient distribution system operation.
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Date Issued
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2017
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Identifier
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CFE0006746, ucf:51856
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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/CFE0006746
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Title
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Public Opinion and the President's Use of Executive Orders: Aggregate- and Individual-Level Analyses Across Time.
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Creator
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Jones, Brett, Lanier, Drew, Knuckey, Jonathan, Ilderton, Nathan, University of Central Florida
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Abstract / Description
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Presidential approval ratings are a political resource that presidents and their advisors hope to influence through strategic action in order to achieve their policy goals (McAvoy 2008, 284). Through 1999, scholarly literature had largely ignored the president's use of unilateral powers. Since Moe and Howell (1999a, 1999b), however, the literature on the unilateral presidency has expanded rapidly. Despite the rapid growth of literature examining the unilateral presidency, and 45 years of...
Show morePresidential approval ratings are a political resource that presidents and their advisors hope to influence through strategic action in order to achieve their policy goals (McAvoy 2008, 284). Through 1999, scholarly literature had largely ignored the president's use of unilateral powers. Since Moe and Howell (1999a, 1999b), however, the literature on the unilateral presidency has expanded rapidly. Despite the rapid growth of literature examining the unilateral presidency, and 45 years of presidential approval ratings literature, literature examining the link between the president's use of unilateral powers and subsequent presidential approval ratings is virtually nonexistent. Existing research has not statistically examined what effect, if any, the president's issuing executive orders has on subsequent job approval ratings. This thesis seeks to address that research gap. By modeling aggregate and individual-level presidential approval ratings, using fixed-effect models, OLS regression, and binary logistic regression, this thesis finds evidence indicating the president's issuing of executive orders has a negative impact on the subsequent presidential job approval ratings that individuals report. If an executive order is salient to the public, presidents receive lower presidential approval ratings from persons of all political parties; however, if the executive order is non-salient then presidents only receive lower presidential approval ratings from members of their own political party. Members of the opposition party report higher presidential approval ratings when the president issued non-salient executive orders. Thus, this thesis concludes that the president's issuing of executive orders has significant effects on subsequent presidential job approval ratings, and future research should be conducted to explore this relationship further.
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Date Issued
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2016
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Identifier
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CFE0006123, ucf:51164
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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/CFE0006123
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Title
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Dynamic feedback pulse shaping for high power chirped pulse amplification system.
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Creator
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Nguyen, Dat, Delfyett, Peter, Rahman, Talat, Richardson, Martin, Schulzgen, Axel, Li, Guifang, University of Central Florida
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Abstract / Description
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The topic of this proposal is the development of high peak power laser sources with a focus on linearly chirped pulse laser sources. In the past decade chirped optical pulses have found a plethora of applications such as photonic analog-to-digital conversion, optical coherence tomography, laser ranging, etc. This dissertation analyzes the aforementioned applications of linearly chirped pulses and their technical requirements, as well as the performance of previously demonstrated parabolic...
Show moreThe topic of this proposal is the development of high peak power laser sources with a focus on linearly chirped pulse laser sources. In the past decade chirped optical pulses have found a plethora of applications such as photonic analog-to-digital conversion, optical coherence tomography, laser ranging, etc. This dissertation analyzes the aforementioned applications of linearly chirped pulses and their technical requirements, as well as the performance of previously demonstrated parabolic pulse shaping approaches. The experimental research addresses the topic of parabolic pulse generation in two distinct ways. First, pulse shaping technique involving a time domain approach is presented, that results in stretched pulses with parabolic profiles with temporal duration of 15 ns. After pulse is shaped into a parabolic intensity profile, the pulse is compressed with DCF fiber spool by 100 times to 80 ps duration at FWHM. A different approach of pulse shaping in frequency domain is performed, in which a spectral processor based on Liquid Crystal on Silicon technology is used. The pulse is stretched to 1.5 ns before intensity mask is applied, resulting in a parabolic intensity profile. Due to frequency to time mapping, its temporal profile is also parabolic. After pulse shaping, the pulse is compressed with a bulk compressor, and subsequently analyzed with a Frequency Resolved Optical Gating (FROG). The spectral content of the compressed pulse is feedback to the spectral processor and used to adjust the spectral phase mask applied on the pulse. The resultant pulse after pulse shaping with feedback mechanism is a Fourier transform, sub-picosecond ultrashort pulse with 5 times increase in peak power.The appendices in this dissertation provide additional material used for the realization of the main research focus of the dissertation. Specification and characterization of major components of equipment and devices used in the experiment are present. The description of Matlab algorithms that was used to calculate required signals for pulse shaping are shown. A brief description of the Labview code used to control the spectral processor will also be illustrated.
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Date Issued
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2013
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Identifier
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CFE0004899, ucf:49642
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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/CFE0004899
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Title
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Determination of Critical Rest Interval using Repeated Sprint Ability Testing.
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Creator
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Lamonica, Michael, Fukuda, David, Hoffman, Jay, Stout, Jeffrey, Fragala, Maren, University of Central Florida
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Abstract / Description
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The critical power (CP) concept has been used to determine the appropriate rest interval during intermittent exercise through the investigation of critical rest interval (CRI). Repeated sprint ability (RSA) testing has been developed to define the athlete's ability to recover and maintain maximal effort during successive bouts. The CP model has been used to understand the physiological responses involved with intermittent exercise delineating between severe and heavy exercise intensity...
Show moreThe critical power (CP) concept has been used to determine the appropriate rest interval during intermittent exercise through the investigation of critical rest interval (CRI). Repeated sprint ability (RSA) testing has been developed to define the athlete's ability to recover and maintain maximal effort during successive bouts. The CP model has been used to understand the physiological responses involved with intermittent exercise delineating between severe and heavy exercise intensity domains. The primary purpose of this study was to determine the CRI from the work-time relationship given by RSA testing using varying work to rest ratios. The secondary purpose was to determine the validity of CRI by evaluation of physiological responses above and below estimated rest interval values during intermittent cycling.Twelve recreationally trained males (mean (&)#177; SD; age 24.1 (&)#177; 3.6yr; height 175.8 (&)#177; 7.0cm; weight 77.6 (&)#177; 12.8kg; V?O2peak 43.3 (&)#177; 5.6ml/kg/min; Body Fat (%) 24.5 (&)#177; 4.4) were recruited for this study. Participants performed a graded exercise test to determine V?O2peak and peak heart rate. Eight participants completed the same three RSA protocols with 6s maximal sprints and varying rest intervals (12-24s) on a cycle ergometer. Intermittent critical power (ICP) was calculated through the linear total work (TW) and time-to-exhaustion (TTE) relationship, whereas CRI was estimated using the average work per sprint and ICP. Seven subjects completed trials above and below estimated CRI to evaluate the validity of this estimate through the examination of the physiological responses. Breath-by-breath oxygen consumption (V?O2) and heart rate (HR) values were recorded during the validation trials. One-way repeated measures analysis of variance (ANOVA) was used to analyze the variables from the RSA trials. Paired samples t-tests were performed to compare performance and physiological variables above or below CRI during the validation trials. Two-way repeated measures ANOVA was used to examined the changes in oxygen consumption (V?O2), HR, mean power (MP), and TW throughout the validation trials. Significant differences (p (<) 0.1) were found for the number of intervals completed, TTE, average work per sprint, peak and mean V?O2 between RSA protocols. Linearity between TW and TTE was r2 = 0.952 (&)#177; 0.081. During the validation trials, TTE was significantly greater in the above versus the below CRI trial (2270.43 (&)#177; 941.15s vs. 1511.00 (&)#177; 811.0s). Furthermore, blood lactate concentration (8.94 (&)#177; 4.89mmol/L vs. 6.56 (&)#177; 3.45mmol/L), AveV?O2 (2.05 (&)#177; 0.36L/min vs. 1.78 (&)#177; 0.26L/min), V?O2peak (2.84 (&)#177; 0.48L/min vs. 2.61 (&)#177; 0.43L/min), and AveHR (151.14 (&)#177; 18.46bpm vs. 138.14 (&)#177; 17.51L/min) were significantly greater in the below CRI trial when compared to the above CRI trial. Significant interactions were found between above and below trials within minimal V?O2 response (F = 6.886, p = 0.024, ?2 = 0.534) to the recovery intervals and maximal HR (F = 4.51, p = 0.016, ?2 = 0.429) response to the work intervals. During the above CRI trial, minimal V?O2 response decreased over time (51-43%V?O2 peak) while maximal HR response achieved a steady state level (81-84%HRpeak). Conversely, minimal V?O2 response during the below CRI trial achieved a steady state level (54-58%V?O2 peak), whereas maximal HR response increased over time (84-90%HRpeak).The relationship between TW and TTE is appropriate for use with RSA testing with varying rest intervals. The differing physiological response during the validation trials may reflect changes in energy system contribution. In conclusion, CRI distinguished between physiological responses related to exercise intensity domains in a manner similar to CP estimates determined from other testing and exercise modalities.
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Date Issued
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2014
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Identifier
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CFE0005645, ucf:50168
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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/CFE0005645
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Title
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Holographic Recording and Applications of Multiplexed Volume Bragg Gratings in Photo-thermo-refractive Glass.
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Creator
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Ott, Daniel, Glebov, Leonid, Zeldovich, Boris, Moharam, Jim, Rahman, Talat, University of Central Florida
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Abstract / Description
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Recent developments in holographic recording of volume Bragg gratings (VBGs) in photo-thermo-refractive (PTR) glass have demonstrated their utility as components in high power laser systems for spectral narrowing, transverse mode control, beam combining, and pulse stretching/compression. VBG structures are capable of diffracting incident light into a single diffraction order with high efficiency given the Bragg condition is met. The Bragg condition depends on both the wavelength and angle of...
Show moreRecent developments in holographic recording of volume Bragg gratings (VBGs) in photo-thermo-refractive (PTR) glass have demonstrated their utility as components in high power laser systems for spectral narrowing, transverse mode control, beam combining, and pulse stretching/compression. VBG structures are capable of diffracting incident light into a single diffraction order with high efficiency given the Bragg condition is met. The Bragg condition depends on both the wavelength and angle of the incident light making VBGs useful for filtering and manipulating both the wavelength and angular spectrum of a source. This dissertation expands upon previous research in PTR VBGs by investigating multiplexed VBGs and their applications in laser systems. Multiplexing involves the integration of several VBGs into the same volume of PTR glass. This process enables the fabrication of splitting and combining elements which have been used for high power beam combining with significantly reduced complexity as compared to other combining schemes. Several configurations of multiplexed beam combiners were demonstrated for both spectral and coherent combining systems with high power results yielding a combined power of 420 W with 96% efficiency. Multiplexing was also used to produce unique phase structures within VBGs. This effect was exploited to create extremely narrowband spectral filters called moir(&)#233; Bragg gratings. The technical challenges of producing moir(&)#233; gratings in bulk glass have revealed new insights into the use of PTR glass as a recording medium and produced devices capable of narrowband filtering of only 15 pm in the near infrared. Experiments were performed using such devices as intra-cavity laser elements for longitudinal mode selection. Investigations have also been made into increasing the level of multiplexing possible within PTR glass. These explorations included scaling the number of beam combining channels, fabrication of integrated multi-notch filters, and generated several other potentially interesting devices for future research. The summation of this work indicates a promising future for multiplexed VBGs in PTR glass.
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Date Issued
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2014
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Identifier
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CFE0005392, ucf:50446
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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/CFE0005392
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Title
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Semiconductor Laser Based on Thermoelectrophotonics.
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Creator
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Liu, Xiaohang, Deppe, Dennis, Vanstryland, Eric, Dogariu, Aristide, Bass, Michael, University of Central Florida
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Abstract / Description
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This dissertation presents to our knowledge the first demonstration of a quantum well (QW) laser monolithically integrated with internal optical pump based on a light emitting diode (LED). The LED with high efficiency is operated in a thermoelectrophotonic (TEP) regime for which it can absorb both its own emitted light and heat. The LED optical pump can reduce internal optical loss in the QW laser, and enables monolithically integrated TEP heat pumps to the semiconductor laser. The design,...
Show moreThis dissertation presents to our knowledge the first demonstration of a quantum well (QW) laser monolithically integrated with internal optical pump based on a light emitting diode (LED). The LED with high efficiency is operated in a thermoelectrophotonic (TEP) regime for which it can absorb both its own emitted light and heat. The LED optical pump can reduce internal optical loss in the QW laser, and enables monolithically integrated TEP heat pumps to the semiconductor laser. The design, growth and fabrication processes of the laser chip are discussed, and its experimental data is presented. In order to further increase the TEP laser efficiency the development of QDs as the active region for TEP edge emitting laser (EEL) is studied. The usage of QD as TEP laser's active region is significant in terms of its low threshold current density, low internal optical loss and high reliability, which are mainly due to low transparency in QD laser. The crystal growth of self-organized QDs in molecular beam epitaxial (MBE) system and characterization of QDs are mentioned. The design, growth, processing and fabrication of a QD laser structure are detailed. The characteristics of laser devices with different cavity length are reported. QD active regions with different amount of material are grown to improve the active region performance. Theoretical calculations based on material parameters and semiconductor physics indicate that with proper design, the combination of high efficiency LED in TEP regime with a QD laser can result in the integrated laser chip power conversion efficiency exceeding unity.
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Date Issued
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2014
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Identifier
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CFE0005369, ucf:50477
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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/CFE0005369
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Title
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rf power amplifier and oscillator design for reliability and variability.
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Creator
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Chen, Shuyu, Yuan, Jiann-Shiun, Sundaram, Kalpathy, Shen, Zheng, Gong, Xun, Wang, Morgan, University of Central Florida
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Abstract / Description
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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
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2013
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Identifier
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CFE0004664, ucf:49894
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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/CFE0004664
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Title
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Peak Power Scaling of Nanosecond Pulses in Thulium based Fiber Lasers.
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Creator
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Gaida, Christian, Richardson, Martin, Shah, Lawrence, Amezcua Correa, Rodrigo, University of Central Florida
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Abstract / Description
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Thulium based fiber lasers represent a promising alternative for pulse energy scaling and highpeak power generation with ytterbium based systems at 1 micrometer. Advantages of thulium arise fromthe operation at longer wavelengths and a large gain bandwidth (1.8-2.1 micrometer). Nonlinear effects,such as self phase modulation, stimulated Raman scattering and stimulated Brillouin scattering generally limit peak power scaling in fiber lasers. The longer wavelength of thulium fiber lasersand...
Show moreThulium based fiber lasers represent a promising alternative for pulse energy scaling and highpeak power generation with ytterbium based systems at 1 micrometer. Advantages of thulium arise fromthe operation at longer wavelengths and a large gain bandwidth (1.8-2.1 micrometer). Nonlinear effects,such as self phase modulation, stimulated Raman scattering and stimulated Brillouin scattering generally limit peak power scaling in fiber lasers. The longer wavelength of thulium fiber lasersand large mode field areas can significantly increase the nonlinear thresholds. Compared to 1 micrometer systems, thulium fiber lasers enable single mode guidance for two times larger mode field diameterin step index fibers. Similar behavior is expected for index guiding thulium doped photonic crystalfibers.In this work a novel thulium doped rod type photonic crystal fiber design with large mode field diameter (>50 micrometer) was first characterized in CW-lasing configuration and then utilized as finalamplifier in a two stage master oscillator power amplifier. The system generated MW-level peakpower at 6.5ns pulse duration and 1kHz repetition rate. This world record performance exemplifiesthe potential of thulium fiber lasers to supersede ytterbium based systems for very high peak powergeneration in the future.As part of this work a computer model for the transient simulation of pulsed amplification inthulium based fiber lasers was developed. The simulations are in good agreement with the experimentalresults. The computer model can be used for efficient optimization of future thulium basedfiber amplifier designs.
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Date Issued
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2013
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Identifier
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CFE0004845, ucf:49699
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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/CFE0004845
Pages