Current Search: Powers (x)
Pages
-
-
Title
-
Developing new power management and High-Reliability Schemes in Data-Intensive Environment.
-
Creator
-
Wang, Ruijun, Wang, Jun, Jin, Yier, DeMara, Ronald, Zhang, Shaojie, Ni, Liqiang, University of Central Florida
-
Abstract / Description
-
With the increasing popularity of data-intensive applications as well as the large-scale computingand storage systems, current data centers and supercomputers are often dealing with extremelylarge data-sets. To store and process this huge amount of data reliably and energy-efficiently,three major challenges should be taken into consideration for the system designers. Firstly, power conservation(-)Multicore processors or CMPs have become a mainstream in the current processormarket because of...
Show moreWith the increasing popularity of data-intensive applications as well as the large-scale computingand storage systems, current data centers and supercomputers are often dealing with extremelylarge data-sets. To store and process this huge amount of data reliably and energy-efficiently,three major challenges should be taken into consideration for the system designers. Firstly, power conservation(-)Multicore processors or CMPs have become a mainstream in the current processormarket because of the tremendous improvement in transistor density and the advancement in semiconductor technology. However, the increasing number of transistors on a single die or chip reveals a super-linear growth in power consumption [4]. Thus, how to balance system performance andpower-saving is a critical issue which needs to be solved effectively. Secondly, system reliability(-)Reliability is a critical metric in the design and development of replication-based big data storagesystems such as Hadoop File System (HDFS). In the system with thousands machines and storagedevices, even in-frequent failures become likely. In Google File System, the annual disk failurerate is 2:88%,which means you were expected to see 8,760 disk failures in a year. Unfortunately,given an increasing number of node failures, how often a cluster starts losing data when beingscaled out is not well investigated. Thirdly, energy efficiency(-)The fast processing speeds of the current generation of supercomputers provide a great convenience to scientists dealing with extremely large data sets. The next generation of (")exascale(") supercomputers could provide accuratesimulation results for the automobile industry, aerospace industry, and even nuclear fusion reactors for the very first time. However, the energy cost of super-computing is extremely high, with a total electricity bill of 9 million dollars per year. Thus, conserving energy and increasing the energy efficiency of supercomputers has become critical in recent years.This dissertation proposes new solutions to address the above three key challenges for currentlarge-scale storage and computing systems. Firstly, we propose a novel power management scheme called MAR (model-free, adaptive, rule-based) in multiprocessor systems to minimize the CPU power consumption subject to performance constraints. By introducing new I/O wait status, MAR is able to accurately describe the relationship between core frequencies, performance and power consumption. Moreover, we adopt a model-free control method to filter out the I/O wait status from the traditional CPU busy/idle model in order to achieve fast responsiveness to burst situations and take full advantage of power saving. Our extensive experiments on a physical testbed demonstrate that, for SPEC benchmarks and data-intensive (TPC-C) benchmarks, an MAR prototype system achieves 95.8-97.8% accuracy of the ideal power saving strategy calculated offline. Compared with baseline solutions, MAR is able to save 12.3-16.1% more power while maintain a comparable performance loss of about 0.78-1.08%. In addition, more simulation results indicate that our design achieved 3.35-14.2% more power saving efficiency and 4.2-10.7% less performance loss under various CMP configurations as compared with various baseline approaches such as LAST, Relax,PID and MPC.Secondly, we create a new reliability model by incorporating the probability of replica loss toinvestigate the system reliability of multi-way declustering data layouts and analyze their potential parallel recovery possibilities. Our comprehensive simulation results on Matlab and SHARPE show that the shifted declustering data layout outperforms the random declustering layout in a multi-way replication scale-out architecture, in terms of data loss probability and system reliability by upto 63% and 85% respectively. Our study on both 5-year and 10-year system reliability equipped with various recovery bandwidth settings shows that, the shifted declustering layout surpasses the two baseline approaches in both cases by consuming up to 79 % and 87% less recovery bandwidth for copyset, as well as 4.8% and 10.2% less recovery bandwidth for random layout.Thirdly, we develop a power-aware job scheduler by applying a rule based control method and takinginto account real world power and speedup profiles to improve power efficiency while adheringto predetermined power constraints. The intensive simulation results shown that our proposed method is able to achieve the maximum utilization of computing resources as compared to baselinescheduling algorithms while keeping the energy cost under the threshold. Moreover, by introducinga Power Performance Factor (PPF) based on the real world power and speedup profiles, we areable to increase the power efficiency by up to 75%.
Show less
-
Date Issued
-
2016
-
Identifier
-
CFE0006704, ucf:51907
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0006704
-
-
Title
-
A Study of Perceptions on Incident Response Exercises, Information Sharing, Situational Awareness, and Incident Response Planning in Power Grid Utilities.
-
Creator
-
Garmon, Joseph, Karwowski, Waldemar, Hancock, Peter, Elshennawy, Ahmad, Wan, Thomas, University of Central Florida
-
Abstract / Description
-
The power grid is facing increasing risks from a cybersecurity attack. Attacks that shut off electricity in Ukraine have already occurred, and successful compromises of the power grid that did not shut off electricity to customers have been privately disclosed in North America. The objective of this study is to identify how perceptions of various factors emphasized in the electric sector affect incident response planning. Methods used include a survey of 229 power grid personnel and the use...
Show moreThe power grid is facing increasing risks from a cybersecurity attack. Attacks that shut off electricity in Ukraine have already occurred, and successful compromises of the power grid that did not shut off electricity to customers have been privately disclosed in North America. The objective of this study is to identify how perceptions of various factors emphasized in the electric sector affect incident response planning. Methods used include a survey of 229 power grid personnel and the use of partial least squares structural equation modeling to identify causal relationships. This study reveals the relationships between perceptions by personnel responsible for cybersecurity, regarding incident response exercises, information sharing, and situational awareness, and incident response planning. The results confirm that the efforts by the industry on these topics have advanced planning for a potential attack.
Show less
-
Date Issued
-
2019
-
Identifier
-
CFE0007805, ucf:52349
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0007805
-
-
Title
-
Design, Simulation and Characterization of Novel Electrostatic Discharge Protection Devices and Circuits in Advanced Silicon Technologies.
-
Creator
-
Liang, Wei, Sundaram, Kalpathy, Fan, Deliang, Jin, Yier, Wei, Lei, Salcedo, Javier, University of Central Florida
-
Abstract / Description
-
Electrostatic Discharge (ESD) has been one of the major reliability concerns in the advanced silicon technologies and it becomes more important with technology scaling. It has been reported that more than 35% of the failures in integrated circuits (ICs) are ESD induced. ESD event is a phenomenon that a finite amount of charges transfer between two objects with different potential in a quite short time. Such event contains a large energy and the ICs without proper ESD protection could be...
Show moreElectrostatic Discharge (ESD) has been one of the major reliability concerns in the advanced silicon technologies and it becomes more important with technology scaling. It has been reported that more than 35% of the failures in integrated circuits (ICs) are ESD induced. ESD event is a phenomenon that a finite amount of charges transfer between two objects with different potential in a quite short time. Such event contains a large energy and the ICs without proper ESD protection could be destroyed easily, so ESD protection solutions are essential to semiconductor industry.ESD protection design consists of on-chip and off-chip ESD protection design, and the research works in this dissertation are all conducted in on-chip level, which incorporate the ESD protection devices and circuits into the microchip, to provide with basic ESD protection from manufacturing to customer use. The basic idea of ESD protection design is to provide a path with low impedance which directs most of the ESD current to flow through itself instead of the core circuit, and the ESD protection path must be robust enough to make sure that it does not fail before the core circuit. In this way, proper design on protection devices and circuits should be considered carefully. To assist the understanding and design of ESD protection, the ESD event in real world has been classified into a few ESD model including Human Body Model (HBM), Machine Model (MM), Charged Device Model (CDM), etc. Some mainstream testing method and industry standard are also introduced, including Transmission Line Pulse (TLP), and IEC 61000-4-2. ESD protection devices including diode, Gate-Grounded N-type MOSFET (GGNMOS), Silicon Controlled Rectifier (SCR) are basic elements for ESD protection design. In this dissertation, the device characteristics in ESD event and their applications are introduced. From the perspective of the whole chip ESD protection design, the concept of circuit level ESD protection and the ESD clamps are also briefly introduced. Technology Computer Aided Design (TCAD) and Simulation Program with Integrated Circuit Emphasis (SPICE) simulation is widely used in ESD protection design. In this dissertation, TCAD and SPICE simulation are carried out for a few times for both of pre-tapeout evaluation on characteristics of the proposed device and circuit and post-tapeout analysis on structure operating mechanism.Automotive electronics has been a popular subject in semiconductor industry, and due to the special requirement of the automotive applications like the capacitive pins, the ESD protection device used in such applications need to be specially designed. In this dissertation, a few SCRs without snapback are discussed in detail. To avoid core circuit damages caused the displacement current induced by the large snapback in conventional SCR, an eliminated/minimized snapback is preferred in a selection of the protection device. Two novel SCRs are proposed for High Voltage (HV), Medium Voltage (MV), and Low Voltage (LV) automotive ESD protection.The typical operating temperature for ICs is up to 125 (&)#186;C, however in automotive applications, the operating temperature may extend up to 850 (&)#186;C. In this way, the characteristics of the ESD protection device under the elevated temperatures will be an essential part to investigate for automotive ESD protection design. In this dissertation, the high temperature characteristics of ESD protection devices including diode and a few SCRs is measured and discussed in detail. TCAD simulation are also conducted to explain the underlying physical mechanism. This work provides with a useful insight and information to ESD protection design in high temperature applications.Besides the high temperature environment, ESD protection are also highly needed for electronics working in other extreme environment like the space. Space is an environment that contains kinds of radiation source and at the same time can generate abundant ESD. The ESD adhering to the space systems could be a potential threat to the space electronics. At the same time, the characteristics of the ESD protection part especially the basic protection device used in the space electronics could be influenced after the irradiation in the space. Therefore, the investigation of the radiation effects on ESD protection devices are necessary. In this dissertation, the total ionizing dose (TID) effects on ESD protection devices are investigated. The devices are irradiated with 1.5 MeV He+ and characterized with TLP tester. The pre- and post-irradiation characteristics are compared and the variation on key ESD parameters are analyzed and discussed. This work offers a useful insight on ESD devices' operation under TID and help with the device designing on ESD protection devices for space electronics.Single ESD protection devices are essential part constructing the ESD protection network, however the optimization on ESD clamp circuit design is also important on building an efficient whole chip ESD protection network. In this dissertation, the design and simulation of a novel voltage triggered ESD detection circuit are introduced. The voltage triggered ESD detection circuit is proposed in a 0.18 um CMOS technology. Comparing with the conventional RC based detection circuit, the proposed circuit realizes a higher triggering efficiency with a much smaller footprint, and is immune to false triggering under fast power-up events. The proposed circuit has a better sensitivity to ESD event and is more reliable in ESD protection applications.The leakage current has been a concern with the scaling down of the thickness of the gate oxide. Therefore, a proper design of the ESD clamp for power rail ESD protection need to be specially considered. In this dissertation, a design of a novel ESD clamp with low leakage current is analyzed. The proposed clamp realized a pretty low leakage current up to 12 nA, and has a smaller footprint than conventional design. It also has a long hold-on time under ESD event and a quick turn-off mechanism for false triggering. SPICE simulation is carried out to evaluate the operation of the proposed ESD clamp.
Show less
-
Date Issued
-
2017
-
Identifier
-
CFE0007126, ucf:52298
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0007126
-
-
Title
-
Neither Teacher nor Scholar: Identity and Agency in a Graduate Teacher's Life.
-
Creator
-
Pierson, Caitlin, Wheeler, Stephanie, Edwards, Dustin, Scott, Blake, University of Central Florida
-
Abstract / Description
-
This thesis examines how graduate student teachers (GTA's) employ agency in order to establish and perform professional identities. Understanding agency as interactional, performative, and acting in a way (")unintended by power(") (Butler, 1997, p. 15), this thesis examines the spatial practices and performances of a graduate student teacher through a mixed methods approach combining video recordings with autoethnography.This project begins by using Lefebvre's (1991) social imaginary to...
Show moreThis thesis examines how graduate student teachers (GTA's) employ agency in order to establish and perform professional identities. Understanding agency as interactional, performative, and acting in a way (")unintended by power(") (Butler, 1997, p. 15), this thesis examines the spatial practices and performances of a graduate student teacher through a mixed methods approach combining video recordings with autoethnography.This project begins by using Lefebvre's (1991) social imaginary to examine the potent arguments being made to and about GTA's from their shared office, using visual rhetorical analysis to examine how this space communicates ideas of identity and place that work at rhetorical purposes counter to the performances GTA's are employing within that space. Exploring how GTA's respond to the social imaginary within space, this thesis conducts an analysis of the tactics employed, using De Certeau (1984) as a framework. Graduate student teachers use spatial practices and performances to make do with the space and the power allotted to them; however, they employ key tactics such as altering body position and vocal tone to turn interactions with students and with each other into dynamic moments for the production of agency.Finally, this thesis argues that, while GTA's use tactics and spatial practices to negotiate the performances and spaces allotted to them, their agency is temporal and limited. Departmental investment in relationships with GTA and integrating them further into the life of the department through apprenticeship can bolster the tenuous agency of the GTA.
Show less
-
Date Issued
-
2018
-
Identifier
-
CFE0007235, ucf:52232
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0007235
-
-
Title
-
Power Scaling of High Power Solid State Lasers.
-
Creator
-
Oh, Bumjin, Richardson, Martin, Soileau, MJ, Chini, Michael, University of Central Florida
-
Abstract / Description
-
The solid-state laser is one of the most widely used lasers in scientific research and industrial applications. This thesis describes detailed investigations of two modern architectures of high power cw solid-state lasers, a 20 W diode-pumped Yb:YAG thin disc laser and 300 W diode-pumped Nd:YAG rod laser. With the thin disc laser architecture, the signal beam must fit to the pump area on the disc defined by the multi-pass diode pump configuration. The beam propagation, beam diameter, phase...
Show moreThe solid-state laser is one of the most widely used lasers in scientific research and industrial applications. This thesis describes detailed investigations of two modern architectures of high power cw solid-state lasers, a 20 W diode-pumped Yb:YAG thin disc laser and 300 W diode-pumped Nd:YAG rod laser. With the thin disc laser architecture, the signal beam must fit to the pump area on the disc defined by the multi-pass diode pump configuration. The beam propagation, beam diameter, phase and thermal effects for various cavity configurations are investigated theoretically and experimentally. In addition, the internal loss, small signal gain, and thermal lensing effect are essential properties to construct the laser system but usually unknown. The theories and methodologies to obtain these properties are presented and the experimental results are compared. In a second phase of the project, the multi-mode and single-mode operation of a high power diode-pumped rod laser system are examined and compared to the thin disc system. Thermal effects on the phase, beam quality and brightness are examined and future applications and improvements considered.
Show less
-
Date Issued
-
2018
-
Identifier
-
CFE0007232, ucf:52221
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0007232
-
-
Title
-
Examining the impact of leader social distance on a multicultural team.
-
Creator
-
DiazGranados, Deborah, Salas, Eduardo, Jentsch, Kimberly, Pritchard, Robert, Piccolo, Ronald, Burke, Shawn, University of Central Florida
-
Abstract / Description
-
Leading multicultural teams is one of the main challenges faced by today's leaders. The advantages often associated with multicultural teams (e.g., collaboration and integration of different knowledge, ideas, and approaches to a task) are often the major challenges in leading these teams. The literature on effective multicultural teams has identified leadership as an important factor for team effectiveness. Therefore, the goal of this study was to examine the effect of leader social distance...
Show moreLeading multicultural teams is one of the main challenges faced by today's leaders. The advantages often associated with multicultural teams (e.g., collaboration and integration of different knowledge, ideas, and approaches to a task) are often the major challenges in leading these teams. The literature on effective multicultural teams has identified leadership as an important factor for team effectiveness. Therefore, the goal of this study was to examine the effect of leader social distance in multicultural teams. A lab study was designed to test the impact of experimentally-manipulated leader social distance (socially close or socially distant) on the relationship between team member diversity and team affect, processes, and performance. Results varied for female and for male teams. Specifically, the nature of the interactions between leadership and team diversity depended on the specific cultural dimension measured and the gender of the team. In the end, the impact of diversity on culture in female teams was improved by close leaders (the relationships were positive), and worsened by distant leaders (the relationships were negative) for team affect, processes and viability. For male teams, the impact of diversity was always negative in both leader conditions; however, in distant leader conditions the relationship was more negative. Implications for theory and practice are discussed along with suggestions for future research.
Show less
-
Date Issued
-
2011
-
Identifier
-
CFE0004100, ucf:49114
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0004100
-
-
Title
-
THREE-PORT MICRO-INVERTER WITH POWER DECOUPLING CAPABILITY FOR PHOTOVOLTAIC (PV) SYSTEMS APPLICATIONS.
-
Creator
-
Harb, Souhib, Batarseh, Issa, University of Central Florida
-
Abstract / Description
-
The Photovoltaic (PV) systems have been realized using different architectures, starting with the string and centralized PV system to the modular PV system. Presently, decentralized inverters are being developed at the PV panel power level (known as AC ÃÂ PV Modules). Such new PV systems are becoming more attractive and many expect this will be the trend of the future. The AC-Module PV system consists of an inverter attached to one PV panel. This integration requires...
Show moreThe Photovoltaic (PV) systems have been realized using different architectures, starting with the string and centralized PV system to the modular PV system. Presently, decentralized inverters are being developed at the PV panel power level (known as AC ÃÂ PV Modules). Such new PV systems are becoming more attractive and many expect this will be the trend of the future. The AC-Module PV system consists of an inverter attached to one PV panel. This integration requires that both devices have the same life-span. Although, the available commercial inverters have a relatively short life-span (10 years) compared to the 25 ÃÂyear PV. It has been stated in literature that the energy storage capacitor (electrolytic type) in the single-phase inverter is the most vulnerable electronic component. Hence, many techniques such as (power decoupling techniques) have been proposed to solve this problem by replacing the large electrolytic capacitor with a small film capacitor. This thesis will present a quick review of these power decoupling techniques, and proposes a new three-port micro-inverter with power decoupling capability for AC-Module PV system applications.
Show less
-
Date Issued
-
2010
-
Identifier
-
CFE0003357, ucf:48474
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0003357
-
-
Title
-
STUDY OF INGAAS LDMOS FOR POWER CONVERSION APPLICATIONS.
-
Creator
-
Liu, Yidong, Yuan, Jiann S., University of Central Florida
-
Abstract / Description
-
In this work an n-channel In0.65Ga0.35As LDMOS with Al2O3 as gate dielectric is investigated. Instead of using traditional Si process for LDMOS, we suggest In0.65Ga0.35As as substitute material due to its higher electron mobility and its promising for power applications. The proposed 0.5-μm channel-length LDMOS cell is studied through device TCAD simulation tools. Due to different gate dielectric, comprehensive comparisons between In0.65Ga0.35As LDMOS and Si LDMOS are made in two ways,...
Show moreIn this work an n-channel In0.65Ga0.35As LDMOS with Al2O3 as gate dielectric is investigated. Instead of using traditional Si process for LDMOS, we suggest In0.65Ga0.35As as substitute material due to its higher electron mobility and its promising for power applications. The proposed 0.5-μm channel-length LDMOS cell is studied through device TCAD simulation tools. Due to different gate dielectric, comprehensive comparisons between In0.65Ga0.35As LDMOS and Si LDMOS are made in two ways, structure with the same cross-sectional dimension, and structure with different thickness of gate dielectric to achieve the same gate capacitance. The on-resistance of the new device shows a big improvement with no degradation on breakdown voltage over traditional device. Also it is indicated from these comparisons that the figure of merit(FOM) Ron·Qg of In0.65Ga0.35As LDMOS shows an average of 91.9% improvement to that of Si LDMOS. To further explore the benefit of using In0.65Ga0.35As LDMOS as switch in power applications, DC-DC buck converter is utilized to observe the performance of LDMOS in terms of power efficiency. The LDMOS performance is experimented with operation frequency of the circuit sweeping in the range from 100 KHz to 100 MHz. It turns out InGaAs LDMOS is good candidate for power applications.
Show less
-
Date Issued
-
2009
-
Identifier
-
CFE0002686, ucf:48217
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0002686
-
-
Title
-
RESEARCH IN HIGH PERFORMANCE AND LOW POWER COMPUTER SYSTEMS FOR DATA-INTENSIVE ENVIRONMENT.
-
Creator
-
Shang, pengju, Wang, Jun, University of Central Florida
-
Abstract / Description
-
The evolution of computer science and engineering is always motivated by the requirements for better performance, power efficiency, security, user interface (UI), etc. The first two factors are potential tradeoffs: better performance usually requires better hardware, e.g., the CPUs with larger number of transistors, the disks with higher rotation speed; however, the increasing number of transistors on the single die or chip reveals super-linear growth in CPU power consumption, and the change...
Show moreThe evolution of computer science and engineering is always motivated by the requirements for better performance, power efficiency, security, user interface (UI), etc. The first two factors are potential tradeoffs: better performance usually requires better hardware, e.g., the CPUs with larger number of transistors, the disks with higher rotation speed; however, the increasing number of transistors on the single die or chip reveals super-linear growth in CPU power consumption, and the change in disk rotation speed has a quadratic effect on disk power consumption. We propose three new systematic approaches, Transactional RAID, data-affinity-aware data placement DAFA and Modeless power management, to tackle the performance problem in Database systems, large scale clusters or cloud platforms, and the power management problem in Chip Multi Processors, respectively. The first design, Transactional RAID (TRAID), is motivated by the fact that in recent years, more storage system applications have employed transaction processing techniques to ensure data integrity and consistency. In transaction processing systems(TPS), log is a kind of redundancy to ensure transaction ACID (atomicity, consistency, isolation, durability) properties and data recoverability. Furthermore, high reliable storage systems, such as redundant array of inexpensive disks (RAID), are widely used as the underlying storage system for Databases to guarantee system reliability and availability with high I/O performance. However, the Databases and storage systems tend to implement their independent fault tolerant mechanisms from their own perspectives and thereby leading to potential high overhead. We observe the overlapped redundancies between the TPS and RAID systems, and propose a novel reliable storage architecture called Transactional RAID (TRAID). TRAID deduplicates this overlap by only logging one compact version (XOR results) of recovery references for the updating data. It minimizes the amount of log content as well as the log flushing overhead, thereby boosts the overall transaction processing performance. At the same time, TRAID guarantees comparable RAID reliability, the same recovery correctness and ACID semantics of traditional transactional processing systems. On the other hand, the emerging myriad data intensive applications place a demand for high-performance computing resources with massive storage. Academia and industry pioneers have been developing big data parallel computing frameworks and large-scale distributed file systems (DFS) widely used to facilitate the high-performance runs of data-intensive applications, such as bio-informatics, astronomy, and high-energy physics. Our recent work reported that data distribution in DFS can significantly affect the efficiency of data processing and hence the overall application performance. This is especially true for those with sophisticated access patterns. For example, Yahoo's Hadoop clusters employs a random data placement strategy for load balance and simplicity. This allows the MapReduce programs to access all the data (without or not distinguishing interest locality) at full parallelism. Our work focuses on Hadoop systems. We observed that the data distribution is one of the most important factors that affect the parallel programming performance. However, the default Hadoop adopts random data distribution strategy, which does not consider the data semantics, specifically, data affinity. We propose a Data-Affinity-Aware (DAFA) data placement scheme to address the above problem. DAFA builds a history data access graph to exploit the data affinity. According to the data affinity, DAFA re-organizes data to maximize the parallelism of the affinitive data, and also subjective to the overall load balance. This enables DAFA to realize the maximum number of map tasks with data-locality. Besides the system performance, power consumption is another important concern of current computer systems. In the U.S. alone, the energy used by servers which could be saved comes to 3.17 million tons of carbon dioxide, or 580,678 cars. However, the goals of high performance and low energy consumption are at odds with each other. An ideal power management strategy should be able to dynamically respond to the change (either linear or nonlinear, or non-model) of workloads and system configuration without violating the performance requirement. We propose a novel power management scheme called MAR (modeless, adaptive, rule-based) in multiprocessor systems to minimize the CPU power consumption under performance constraints. By using richer feedback factors, e.g. the I/O wait, MAR is able to accurately describe the relationships among core frequencies, performance and power consumption. We adopt a modeless control model to reduce the complexity of system modeling. MAR is designed for CMP (Chip Multi Processor) systems by employing multi-input/multi-output (MIMO) theory and per-core level DVFS (Dynamic Voltage and Frequency Scaling).
Show less
-
Date Issued
-
2011
-
Identifier
-
CFE0003910, ucf:48749
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0003910
-
-
Title
-
Thermodynamic Analysis and Optimization of Supercritical Carbon Dioxide Brayton Cycles.
-
Creator
-
Mohagheghi, Mahmood, Kapat, Jayanta, Kassab, Alain, Das, Tuhin, Swami, Muthusamy, University of Central Florida
-
Abstract / Description
-
The power generation industry is facing new challenging issues regarding accelerating growth of electricity demand, fuel cost and environmental pollution. These challenges accompanied by concerns of energy resources becoming scarce necessitate searching for sustainable and economically competitive solutions to supply the future electricity demand. To this end, supercritical carbon dioxide (S-CO2) Brayton cycles present great promise particularly in high temperature concentrated solar power ...
Show moreThe power generation industry is facing new challenging issues regarding accelerating growth of electricity demand, fuel cost and environmental pollution. These challenges accompanied by concerns of energy resources becoming scarce necessitate searching for sustainable and economically competitive solutions to supply the future electricity demand. To this end, supercritical carbon dioxide (S-CO2) Brayton cycles present great promise particularly in high temperature concentrated solar power (CSP) and waste heat recovery (WHR) applications. With this regard, this dissertation is intended to perform thorough thermodynamic analyses and optimization of S-CO2 Brayton cycles for both of these applications.A modeling tool has been developed, which enables one to predict and analyze the thermodynamic performance of the S-CO2 Brayton cycles in various configurations employing recuperation, recompression, intercooling and reheating. The modeling tool is fully flexible in terms of encompassing the entire feasible design domain and rectifying possible infeasible solutions. Moreover, it is computationally efficient in order to handle time consuming optimization problems. A robust optimization tool has also been developed by employing the principles of genetic algorithm. The developed genetic algorithm code is capable of optimizing non-linear systems with several decision variables simultaneously, and without being trapped in local optimum points.Two optimization schemes, i.e. single-objective and multi-objective, are considered in optimizing the S-CO2 cycles for high temperature solar tower applications. In order to reduce the size and cost of solar block, the global maximum efficiency of the power block should be realized. Therefore, the single-objective optimization scheme is considered to find the optimum design points that correspond to the global maximum efficiency of S-CO2 cycles. Four configurations of S-CO2 Brayton cycles are investigated, and the optimum design point for each configuration is determined. Ultimately, the effects of recompression, reheating, and intercooling on the thermodynamic performance of the recuperated S-CO2 Brayton cycle are analyzed. The results reveal that the main limiting factors in the optimization process are maximum cycle temperature, minimum heat rejection temperature, and pinch point temperature difference. The maximum cycle pressure is also a limiting factor in all studied cases except the simple recuperated cycle. The optimized cycle efficiency varies from 55.77% to 62.02% with consideration of reasonable component performances as we add recompression, reheat and intercooling to the simple recuperated cycle (RC). Although addition of reheating and intercooling to the recuperated recompression cycle (RRC) increases the cycle efficiency by about 3.45 percent points, the simplicity of RC and RRC configurations makes them more promising options at this early development stage of S-CO2 cycles, and are used for further studies in this dissertation.The results of efficiency maximization show that achieving the highest efficiency does not necessarily coincide with the highest cycle specific power. In addition to the efficiency, the specific power is also an important parameter when it comes to investment and decision making since it directly affects the power generation capacity, the size of components and the cost of power blocks. Consequently, the multi-objective optimization scheme is devised to simultaneously maximize both the cycle efficiency and specific power in the simple recuperated and recuperated recompression configurations. The optimization results are presented in the form of two optimum trade-off curves, also known as Pareto fronts, which enable decision makers to choose their desired compromise between the objectives, and to avoid naive solution points obtained from a single-objective optimization approach. Moreover, the comparison of the Pareto optimal fronts associated with the studied configurations reveals the optimum operational region of the recompression configuration where it presents superior performance over the simple recuperated cycle.Considering the extensive potential of waste heat recovery from energy intensive industries and stand-alone gas turbines, this dissertation also investigates the optimum design point of S-CO2 Brayton cycles for a wide range of waste heat source temperatures (500 K to 1100 K). Once again, the simple recuperated and recuperated recompression configurations are selected for this application. The utilization of heat in WHR applications is fundamentally different from that in closed loop heat source applications. The temperature pinching issues are recognized in the waste recovery heat exchangers, which brings about a trade-off between the cycle efficiency and amount of recovered heat. Therefore, maximization of net power output for a given waste heat source is of paramount practical interest rather than the maximization of cycle efficiency. The results demonstrate that by changing the heat source temperature from one application to another, the variation of optimum pressure ratio is insignificant. However, the optimum CO2 to waste gas mass flow ratio and turbine inlet temperature should properly be adjusted. The RRC configuration provides minor increase in power output as compared to RC configuration. Although cycle efficiencies as high as 34.8% and 39.7% can be achieved in RC and RRC configurations respectively, the overall conversion efficiency is less than 26% in RRC and 24.5% in RC.
Show less
-
Date Issued
-
2015
-
Identifier
-
CFE0006044, ucf:50993
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0006044
-
-
Title
-
Fiber Optimization for Operation Beyond Transverse Mode Instability Limitations.
-
Creator
-
Bradford, Joshua, Richardson, Martin, Gaume, Romain, Amezcua Correa, Rodrigo, Shah, Lawrence, University of Central Florida
-
Abstract / Description
-
Transverse Mode Instabilities (TMIs) stand as a fundamental limitation to power and brightness scaling in laser systems based upon optical fiber technologies. This work comprises experimental and theoretical investigations into fiber laser design that should minimize the effects of Stimulated Thermal Rayleigh Scattering. Theoretical discussions and simulations focus on how fiber parameters affect transverse mode coupling. These include core geometry optimization, pump geometry optimization,...
Show moreTransverse Mode Instabilities (TMIs) stand as a fundamental limitation to power and brightness scaling in laser systems based upon optical fiber technologies. This work comprises experimental and theoretical investigations into fiber laser design that should minimize the effects of Stimulated Thermal Rayleigh Scattering. Theoretical discussions and simulations focus on how fiber parameters affect transverse mode coupling. These include core geometry optimization, pump geometry optimization, in addition to the effects of HOM content and losses on the TMI threshold. Experimentally, a high-power laser facility is commissioned with beam quality diagnostics to quantify the thresholds of the onset of modal interferences and their impacts on beam quality. These diagnostics include high-resolution Fourier Transform Interferometry (FTI) and in-situ power-in-the-bucket measurements. The design and characterization capabilities developed here are crucial to the development of next-generation high-power fiber laser capabilities.
Show less
-
Date Issued
-
2018
-
Identifier
-
CFE0006980, ucf:51646
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0006980
-
-
Title
-
Assessing the Effectiveness of Workload Measures in the Nuclear Domain.
-
Creator
-
Mercado, Joseph, Reinerman, Lauren, Hancock, Peter, Lackey, Stephanie, Szalma, James, University of Central Florida
-
Abstract / Description
-
An operator's performance and mental workload when interacting with a complex system, such as the main control room (MCR) of a nuclear power plant (NPP), are major concerns when seeking to accomplish safe and successful operations. The impact of performance on operator workload is one of the most widely researched areas in human factors science with over five hundred workload articles published since the 1960s (Brannick, Salas, (&) Prince, 1997; Meshkati (&) Hancock, 2011). Researchers have...
Show moreAn operator's performance and mental workload when interacting with a complex system, such as the main control room (MCR) of a nuclear power plant (NPP), are major concerns when seeking to accomplish safe and successful operations. The impact of performance on operator workload is one of the most widely researched areas in human factors science with over five hundred workload articles published since the 1960s (Brannick, Salas, (&) Prince, 1997; Meshkati (&) Hancock, 2011). Researchers have used specific workload measures across domains to assess the effects of taskload. However, research has not sufficiently assessed the psychometric properties, such as reliability, validity, and sensitivity, which delineates and limits the roles of these measures in workload assessment (Nygren, 1991). As a result, there is no sufficiently effective measure for indicating changes in workload for distinct tasks across multiple domains (Abich, 2013). Abich (2013) was the most recent to systematically test the subjective and objective workload measures for determining the universality and sensitivity of each alone or in combination. This systematic approach assessed taskload changes within three tasks in the context of a military intelligence, surveillance, and reconnaissance (ISR) missions. The purpose for the present experiment was to determine if certain workload measures are sufficiently effective across domains by taking the findings from one domain (military) and testing whether those results hold true in a different domain, that of nuclear. Results showed that only two measures (NASA-TLX frustration and fNIR) were sufficiently effective at indicating workload changes between the three task types in the nuclear domain, but many measures were statistically significant. The results of this research effort combined with the results from Abich (2013) highlight an alarming problem. The ability of subjective and physiological measures to indicate changes in workload varies across tasks (Abich, 2013) and across domain. A single measure is not able to measure the complex construct of workload across different tasks within the same domain or across domains. This research effort highlights the importance of proper methodology. As researchers, we have to identify the appropriate workload measure for all tasks regardless of the domain by investigating the effectiveness of each measure. The findings of the present study suggest that responsible science include evaluating workload measures before use, not relying on prior research or theory. In other words, results indicate that it is only acceptable to use a measure based on prior findings if research has tested that measure on the exact task and manipulations within that specific domain.
Show less
-
Date Issued
-
2014
-
Identifier
-
CFE0005666, ucf:50188
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0005666
-
-
Title
-
Perovskite catalysts enhanced combustion on porous media and thermoelectric power conversion.
-
Creator
-
Robayo, Manuel, Orlovskaya, Nina, Chen, Ruey-Hung, Kapat, Jayanta, Vasu Sumathi, Subith, University of Central Florida
-
Abstract / Description
-
A combustion chamber incorporating a high temperature porous matrix was design and tested. The effects and merits of combining combustion on porous media and catalytic enhancement were explored, in addition to the proof of concept of integrating these technologies with simple heat engines, such as thermoelectric generators, to generate efficient and reliable power. The direct observation of the flame during the combustion becomes possible due to a specially designed stainless steel chamber...
Show moreA combustion chamber incorporating a high temperature porous matrix was design and tested. The effects and merits of combining combustion on porous media and catalytic enhancement were explored, in addition to the proof of concept of integrating these technologies with simple heat engines, such as thermoelectric generators, to generate efficient and reliable power. The direct observation of the flame during the combustion becomes possible due to a specially designed stainless steel chamber incorporating a quartz window where the initiation and propagation of the combustion reaction/flame was directly visible. The simple design of the combustion chamber allowed for a series of thermocouples to be arranged on the central axis of the porous media. With the thermocouples as output and two flow controllers controlling the volumetric flow of fuel and air as input, it was possible to explore the behavior of the flame at different volumetric flow ranges and fuel to air ratios. Additionally the design allowed for thermoelectric modules to be placed in the walls of the combustion chamber. Using combustion as a heat source and passive fins for cooling, the device was able to generate enough power to power a small portable electronic device. The effects of La-Sr-Fe-Cr-Ru based perovskite catalysts, on matrix stabilized combustion in a porous ceramic media were also explored. Highly porous silicon carbide ceramics are used as a porous media for a catalytically enhanced superadiabatic combustion of a lean mixture of methane and air. Perovskite catalytic enhancement of SiC porous matrix with La0.75Sr0.25Fe0.6Cr0.35Ru0.05O3, La0.75Sr0.25Fe0.6Cr0.4O3, La0.75Sr0.25Fe0.95Ru0.05O3, La0.75Sr0.05Cr0.95Ru0.05O3, and LaFe0.95Ru0.05O3 were used to enhance combustion. The flammability limits of the combustion of methane and air were explored using both inert and catalytically enhanced surfaces of the porous ceramic media. By coating the SiC porous media with perovskite catalysts it was possible to lower the minimum stable equivalence ratio and achieve more efficient combustion.
Show less
-
Date Issued
-
2014
-
Identifier
-
CFE0005543, ucf:50315
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0005543
-
-
Title
-
Lateral Power MOSFETs Hardened Against Single Event Radiation Effects.
-
Creator
-
Shea, Patrick, Shen, Zheng, Yuan, Jiann-Shiun, Malocha, Donald, University of Central Florida
-
Abstract / Description
-
The underlying physical mechanisms of destructive single event effects (SEE) from heavy ion radiation have been widely studied in traditional vertical double-diffused power MOSFETs (VDMOS). Recently lateral double-diffused power MOSFETs (LDMOS), which inherently provide lower gate charge than VDMOS, have become an attractive option for MHz-frequency DC-DC converters in terrestrial power electronics applications. There are growing interests in extending the LDMOS concept into radiation-hard...
Show moreThe underlying physical mechanisms of destructive single event effects (SEE) from heavy ion radiation have been widely studied in traditional vertical double-diffused power MOSFETs (VDMOS). Recently lateral double-diffused power MOSFETs (LDMOS), which inherently provide lower gate charge than VDMOS, have become an attractive option for MHz-frequency DC-DC converters in terrestrial power electronics applications. There are growing interests in extending the LDMOS concept into radiation-hard space applications. Since the LDMOS has a device structure considerably different from VDMOS, the well studied single event burn-out (SEB) or single event gate rapture (SEGR) response of VDMOS cannot be simply assumed for LDMOS devices without further investigation. A few recent studies have begun to investigate ionizing radiation effects in LDMOS devices, however, these studies were mainly focused on displacement damage and total ionizing dose (TID) effects, with very limited data reported on the heavy ion SEE response of these devices. Furthermore, the breakdown voltage of the LDMOS devices in these studies was limited to less than 80 volts (mostly in the range of 20-30 volts), considerably below the voltage requirement for some space power applications. In this work, we numerically and experimentally investigate the physical insights of SEE in two different fabricated LDMOS devices designed by the author and intended for use in radiation hard applications. The first device is a 24 V Resurf LDMOS fabricated on P-type epitaxial silicon on a P+ silicon substrate. The second device is a much different 150 V SOI Resurf LDMOS fabricated on a 1.0 micron thick N-type silicon-on-insulator substrate with a 1.0 micron thick buried silicon dioxide layer on an N-type silicon handle wafer. Each device contains internal features, layout techniques, and process methods designed to improve single event and total ionizing dose radiation hardness. Technology computer aided design (TCAD) software was used to develop the transistor design and fabrication process of each device and also to simulate the device response to heavy ion radiation. Using these simulations in conjunction with experimentally gathered heavy ion radiation test data, we explain and illustrate the fundamental physical mechanisms by which destructive single event effects occur in these LDMOS devices. We also explore the design tradeoffs for making an LDMOS device resistant to destructive single event effects, both in terms of electrical performance and impact on other radiation hardness metrics.
Show less
-
Date Issued
-
2011
-
Identifier
-
CFE0004165, ucf:49044
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0004165
-
-
Title
-
DESIGN AND MODELING OF RADIATION HARDENED LDMOSFET FOR SPACE CRAFT POWER SYSTEMS.
-
Creator
-
Shea, Patrick, Shen, John, University of Central Florida
-
Abstract / Description
-
NASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching...
Show moreNASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching performance, development and manufacturing costs, and total mass of power electronics systems. Availability of a hardened fast-switching power MOSFET will allow space-borne power electronics to approach the current level of terrestrial technology, thereby facilitating the use of more modern digital electronic systems in space. It is believed that the use of a p+/p-epi starting material for the LDMOS will offer better hardness against single-event burnout (SEB) and single-event gate rupture (SEGR) when compared to vertical devices fabricated on an n+/n-epi material. By placing a source contact on the bottom-side of the p+ substrate, much of the hole current generated by a heavy ion strike will flow away from the dielectric gate, thereby reducing electrical stress on the gate and decreasing the likelihood of SEGR. Similarly, the device is hardened against SEB by the redirection of hole current away from the base of the device's parasitic bipolar transistor. Total dose hardness is achieved by the use of a standard complementary metal-oxide semiconductor (CMOS) process that has shown proven hardness against total dose radiation effects.
Show less
-
Date Issued
-
2007
-
Identifier
-
CFE0001966, ucf:47468
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0001966
-
-
Title
-
ALGORITHMS FOR DISCOVERING COMMUNITIES IN COMPLEX NETWORKS.
-
Creator
-
Balakrishnan, Hemant, Deo, Narsingh, University of Central Florida
-
Abstract / Description
-
It has been observed that real-world random networks like the WWW, Internet, social networks, citation networks, etc., organize themselves into closely-knit groups that are locally dense and globally sparse. These closely-knit groups are termed communities. Nodes within a community are similar in some aspect. For example in a WWW network, communities might consist of web pages that share similar contents. Mining these communities facilitates better understanding of their evolution and...
Show moreIt has been observed that real-world random networks like the WWW, Internet, social networks, citation networks, etc., organize themselves into closely-knit groups that are locally dense and globally sparse. These closely-knit groups are termed communities. Nodes within a community are similar in some aspect. For example in a WWW network, communities might consist of web pages that share similar contents. Mining these communities facilitates better understanding of their evolution and topology, and is of great theoretical and commercial significance. Community related research has focused on two main problems: community discovery and community identification. Community discovery is the problem of extracting all the communities in a given network, whereas community identification is the problem of identifying the community, to which, a given set of nodes belong. We make a comparative study of various existing community-discovery algorithms. We then propose a new algorithm based on bibliographic metrics, which addresses the drawbacks in existing approaches. Bibliographic metrics are used to study similarities between publications in a citation network. Our algorithm classifies nodes in the network based on the similarity of their neighborhoods. One of the drawbacks of the current community-discovery algorithms is their computational complexity. These algorithms do not scale up to the enormous size of the real-world networks. We propose a hash-table-based technique that helps us compute the bibliometric similarity between nodes in O(m ?) time. Here m is the number of edges in the graph and ?, the largest degree. Next, we investigate different centrality metrics. Centrality metrics are used to portray the importance of a node in the network. We propose an algorithm that utilizes centrality metrics of the nodes to compute the importance of the edges in the network. Removal of the edges in ascending order of their importance breaks the network into components, each of which represent a community. We compare the performance of the algorithm on synthetic networks with a known community structure using several centrality metrics. Performance was measured as the percentage of nodes that were correctly classified. As an illustration, we model the ucf.edu domain as a web graph and analyze the changes in its properties like densification power law, edge density, degree distribution, diameter, etc., over a five-year period. Our results show super-linear growth in the number of edges with time. We observe (and explain) that despite the increase in average degree of the nodes, the edge density decreases with time.
Show less
-
Date Issued
-
2006
-
Identifier
-
CFE0001473, ucf:47085
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0001473
-
-
Title
-
INTEGRATED WAVELENGTH STABILIZATION OF BROAD AREA SEMICONDUCTOR LASERS USING A DUAL GRATING REFLECTOR.
-
Creator
-
O'Daniel, Jason, Johnson, Eric, University of Central Florida
-
Abstract / Description
-
A new fully integrated wavelength stabilization scheme based on grating-coupled surface-emitting lasers is explored. This wavelength stabilization scheme relies on two gratings. The first grating is fabricated on the p-side of the semiconductor laser in close proximity to the laser waveguide such that it couples light out of the guided mode of the waveguide into a propagating mode in the substrate; this grating is known as the grating coupler. The second grating is fabricated on the n-side of...
Show moreA new fully integrated wavelength stabilization scheme based on grating-coupled surface-emitting lasers is explored. This wavelength stabilization scheme relies on two gratings. The first grating is fabricated on the p-side of the semiconductor laser in close proximity to the laser waveguide such that it couples light out of the guided mode of the waveguide into a propagating mode in the substrate; this grating is known as the grating coupler. The second grating is fabricated on the n-side of the substrate such that for the stabilization wavelength, this second grating operates in the Littrow condition and is known as the feedback grating. Furthermore with the proper design of the two gratings, the feedback grating will operate under total internal reflection conditions allowing a near unity retro-reflection of the light of the stabilization wavelength. The grating coupler and feedback grating together comprise a dual grating reflector (DGR). The DGR wavelength stabilization scheme is investigated both theoretically by means of numerical modeling and experimentally by integration of a DGR as a wavelength selective reflector into a single quantum well semiconductor laser with a gain peak centered at 975nm. Numerical modeling predicts a peak reflection of approximately 70% including losses and a spectral width of 0.3nm. The integration of a DGR into a semiconductor laser proved both the efficacy of the scheme and also allowed us to experimentally determine the effective reflectivity to be on the order of 62%; the spectral width of light output from these devices is typically on the order of 0.2nm. Furthermore, these devices had light-current characteristic slopes greater than 0.84W/A operating under continuous wave conditions. The DGR was then modified to provide a reflection with two spectral peaks. A semiconductor device incorporating this dual wavelength DGR was fabricated and tested. These devices showed a peak optical power of in excess of 5.5W and a light-current characteristic slope of 0.86W/A in quasi continuous wave operation; these devices also exhibit a large operating current range in which both wavelengths have comparable output powers. Another modified DGR design was investigated for the purpose of providing an even narrower spectral reflection. Devices incorporating this modified design provided an output with a spectral width as narrow as 0.06nm. DGRs were also integrated into an extremely broad area device of an unorthodox geometry; square devices that lase in two orthogonal directions were fabricated and tested. The last idea investigated was combining a DGR wavelength stabilized laser with a tapered semiconductor optical amplifier into a master oscillator power amplifier device, with the optical coupling between the two components provided by identical grating couplers disposed on the p-side surfaces of each of the devices. These master oscillator power amplifiers provide a peak power of 32W when operating under quasi continuous wave operation.
Show less
-
Date Issued
-
2006
-
Identifier
-
CFE0001392, ucf:47004
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0001392
-
-
Title
-
LOW POWER CMOS CIRCUIT DESIGN AND RELIABILITY ANALYSIS FOR WIRELESS MEMS SENSORS.
-
Creator
-
Sadat, Md Anwar, Yuan, Jiann, University of Central Florida
-
Abstract / Description
-
A sensor node 'AccuMicroMotion' is proposed that has the ability to detect motion in 6 degrees of freedom for the application of physiological activity monitoring. It is expected to be light weight, low power, small and cheap. The sensor node may collect and transmit 3 axes of acceleration and 3 axes of angular rotation signals from MEMS transducers wirelessly to a nearby base station while attached to or implanted in human body. This dissertation proposes a wireless electronic system-on-a...
Show moreA sensor node 'AccuMicroMotion' is proposed that has the ability to detect motion in 6 degrees of freedom for the application of physiological activity monitoring. It is expected to be light weight, low power, small and cheap. The sensor node may collect and transmit 3 axes of acceleration and 3 axes of angular rotation signals from MEMS transducers wirelessly to a nearby base station while attached to or implanted in human body. This dissertation proposes a wireless electronic system-on-a-single-chip to implement the sensor in a traditional CMOS process. The system is low power and may operate 50 hours from a single coin cell battery. A CMOS readout circuit, an analog to digital converter and a wireless transmitter is designed to implement the proposed system. In the architecture of the 'AccuMicroMotion' system, the readout circuit uses chopper stabilization technique and can resolve DC to 1 KHz and 200 nV signals from MEMS transducers. The base band signal is digitized using a 10-bit successive approximation register analog to digital converter. Digitized outputs from up to nine transducers can be combined in a parallel to serial converter for transmission by a 900 MHz RF transmitter that operates in amplitude shift keying modulation technique. The transmitter delivers a 2.2 mW power to a 50 Ù antenna. The system consumes an average current of 4.8 mA from a 3V supply when 6 sensors are in operation and provides an overall 60 dB dynamic range. Furthermore, in this dissertation, a methodology is developed that applies accelerated electrical stress on MOS devices to extract BSIM3 models and RF parameters through measurements to perform comprehensive study, analysis and modeling of several analog and RF circuits under hot carrier and breakdown degradation.
Show less
-
Date Issued
-
2004
-
Identifier
-
CFE0000304, ucf:46318
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0000304
-
-
Title
-
COMPARISON OF SINGLE STAGE AND TWO STAGE STAGE GRID-TIE INVERTERS.
-
Creator
-
Mansfield, Keith, Batarseh, Issa, University of Central Florida
-
Abstract / Description
-
This thesis compares two methods of designing grid-tie inverters. The first design topology is a traditional two stage approach consisting of an isolated DC-DC converter on the input followed by a high switching frequency SPWM (Sinusoidal Pulse Width Modulation) stage to produce the required low frequency sine wave output. The novel second design approach employs a similar DC-DC input stage capable of being modulated to provide a rectified sine wave output voltage/current waveform. This stage...
Show moreThis thesis compares two methods of designing grid-tie inverters. The first design topology is a traditional two stage approach consisting of an isolated DC-DC converter on the input followed by a high switching frequency SPWM (Sinusoidal Pulse Width Modulation) stage to produce the required low frequency sine wave output. The novel second design approach employs a similar DC-DC input stage capable of being modulated to provide a rectified sine wave output voltage/current waveform. This stage is followed by a simple low frequency switched Unfolding Stage to recreate the required sine wave output. Both of the above designs have advantages and disadvantages depending on operating parameters. The following work will compare the Unfolding Output Stage and the SPWM Output Stage at various power levels and power densities. Input stage topologies are similarly examined in order to determine the best design approach for each output stage under consideration.
Show less
-
Date Issued
-
2007
-
Identifier
-
CFE0001783, ucf:47258
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0001783
-
-
Title
-
INTEGRATED TOPOLOGIES AND DIGITAL CONTROL FOR SATELLITE POWER MANAGEMENT AND DISTRIBUTION SYSTEMS.
-
Creator
-
Al-Atrash, Hussam, Batarseh, Issa, University of Central Florida
-
Abstract / Description
-
This work is focused on exploring advanced solutions for space power management and distribution (PMAD) systems. As spacecraft power requirements continue to increase, paralleled by the pressures for reducing cost and overall system weight, power electronics engineers will continue to face major redesigns of the space power systems in order to meet such challenges. Front-end PMAD systems, used to interface the solar sources and battery backup to the distribution bus, need to be designed with...
Show moreThis work is focused on exploring advanced solutions for space power management and distribution (PMAD) systems. As spacecraft power requirements continue to increase, paralleled by the pressures for reducing cost and overall system weight, power electronics engineers will continue to face major redesigns of the space power systems in order to meet such challenges. Front-end PMAD systems, used to interface the solar sources and battery backup to the distribution bus, need to be designed with increased efficiency, reliability, and power density. A new family of integrated single-stage power converter structures is introduced here. This family allows the interface and control of multiple power sources and storage devices in order to optimize utilization of available resources. Employing single-stage power topologies, these converters control power flow efficiently and cost-effectively. This is achieved by modifying the operation and control strategies of isolated soft-switched half-bridge and full-bridge converters--two of the most popular two-port converter topologies. These topologies are reconfigured and utilized to realize three power processing paths. These paths simultaneously utilize the power devices, allowing increased functionality while promising reduced losses and enhanced power densities. Each of the proposed topologies is capable of performing simultaneous control of two of its three ports. Control objectives include battery or ultra-capacitor charge regulation, solar array maximum power point tracking (MPPT), and/or bus voltage regulation. Another advantage of the proposed power structure is that current engineering design concepts can be used to optimize the new topologies in a fashion similar to the mother topologies. This includes component selection and magnetic design procedures, as well as achieving soft-switching for increased efficiency at higher switching frequencies. Galvanic isolation of the load port through high-frequency transformers provides design flexibility for high step-up/step-down conversion ratios. It further allows the converters to be used as power electronics building blocks (PEBB) with outputs connected in different series/parallel combinations to meet different load requirements. Utilizing such converters promises significant savings in size, weight, and costs of the power management system as well as the devices it manages. Chapter 1 of this dissertation provides an introduction to the requirements, challenges, and trends of space PMAD. A review of existing multi-port converter technologies and digital control techniques is given in Chapter 2. Chapter 3 discusses different PMAD system architectures. It outlines the basic concepts used for PMAD integration and discusses the potential for improvement. Chapters 4 and 5 present and discuss the operation and characteristics of three different integrated multi-port converters. Chapter 6 presents improved methods for practical digital control of switching converters, which are especially useful in complex multi-objective controllers used for PMAD. This is followed by conclusions and suggested future work.
Show less
-
Date Issued
-
2007
-
Identifier
-
CFE0001784, ucf:47283
-
Format
-
Document (PDF)
-
PURL
-
http://purl.flvc.org/ucf/fd/CFE0001784
Pages