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- Title
- RESOURCE BANKING: AN ENERGY-EFFICIENT, RUN-TIME ADAPTIVE PROCESSOR DESIGN TECHNIQUE.
- Creator
-
Staples, Jacob, Heinrich, Mark, University of Central Florida
- Abstract / Description
-
From the earliest and simplest scalar computation engines to modern superscalar out-of-order processors, the evolution of computational machinery during the past century has largely been driven by a single goal: performance. In today's world of cheap, billion-plus transistor count processors and with an exploding market in mobile computing, a design landscape has emerged where energy efficiency, arguably more than any other single metric, determines the viability of a processor for a given...
Show moreFrom the earliest and simplest scalar computation engines to modern superscalar out-of-order processors, the evolution of computational machinery during the past century has largely been driven by a single goal: performance. In today's world of cheap, billion-plus transistor count processors and with an exploding market in mobile computing, a design landscape has emerged where energy efficiency, arguably more than any other single metric, determines the viability of a processor for a given application. The historical emphasis on performance has left modern processors bloated and over provisioned for everyday tasks in the hope that during computationally intensive periods some performance improvement will be observed. This work explores an energy-efficient processor design technique that ensures even a highly over provisioned out-of-order processor has only as many of its computational resources active as it requires for efficient computation at any given time. Specifically, this paper examines the feasibility of a dynamically banked register file and reorder buffer with variable banking policies that enable unused rename registers or reorder buffer entries to be voltage gated (turned off) during execution to save power. The impact of bank placement, turn-off and turn-on policies as well as rail stabilization latencies for this approach are explored for high-performance desktop and server designs as well as low-power mobile processors.
Show less - Date Issued
- 2011
- Identifier
- CFE0003991, ucf:48675
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003991
- Title
- Optimization of Glycerol or Biodiesel Waste Prefermentation to Improve EBPR.
- Creator
-
Ghasemi, Marzieh, Randall, Andrew, Duranceau, Steven, Lee, Woo Hyoung, Jimenez, Jose, University of Central Florida
- Abstract / Description
-
The enhanced biological phosphorus removal (EBPR) process efficiency relies on different operational and process conditions especially the type of carbon source available in the wastewater. Acetic acid and propionic acid are the two major volatile fatty acids (VFAs) found in domestic wastewater which can drive biological phosphorus (P) removal to the desired level. However, often domestic wastewater does not have a sufficient amount of VFAs. Due to high acetate and propionate production-cost,...
Show moreThe enhanced biological phosphorus removal (EBPR) process efficiency relies on different operational and process conditions especially the type of carbon source available in the wastewater. Acetic acid and propionic acid are the two major volatile fatty acids (VFAs) found in domestic wastewater which can drive biological phosphorus (P) removal to the desired level. However, often domestic wastewater does not have a sufficient amount of VFAs. Due to high acetate and propionate production-cost, it is not economic to add acetate and propionate directly in full-scale wastewater treatment plants. This brought up the idea of using external carbon sources (e. g. molasses has been used successfully) in EBPR systems that can be converted to VFAs through a fermentation process. On the other hand, biodiesel fuels have been produced increasingly over the last decade. Crude glycerol is a biodiesel production major by-product that can be used as an external carbon source in wastewater treatment plant. Therefore, the main objective of this research is to optimize the glycerol/biodiesel waste fermentation process' operational conditions in pursuit of producing more favorable fermentation end-products (i. e. a mixture of acetic acid and propionic acid) by adding glycerol to a prefermenter versus direct addition to the anaerobic zone or fermentation with waste activated sludge. For this reason, different prefermenter parameters namely: mixing intensity, pH, temperature and solids retention time (SRT), were studied in a small scale fermentation media (serum bottles) and bench scale semi-continuous batch prefermenters. Experimental results revealed that glycerol/biodiesel waste fermentation resulted in a significant amount of VFAs production with propionic acid as the superior end-product followed by acetic acid and butyric acid. The VFA production was at its highest level when the initial pH was adjusted to 7 and 8.5. However, the optimum pH with respect to propionic acid production was 7. Increasing the temperature in serum bottles favored the total VFA production, specifically in the form of propionic acid. Regarding the mixing energy inconsistent results were obtained in the serum bottles compared to the bench scale prefermenters. The VFA production in mixed serum bottles at 200 rpm was higher than that of un-mixed ones. On the other hand, the unmixed or slowly mixed bench scale prefermenters showed higher VFA production than the mixed reactors. However, the serum bottles did not operate long enough to account for biomass acclimation and other long-term effects that the prefermenter experiments could account for. As a consequence one of the most important and consistently results was that VFA production was significantly enhanced by reducing mixing intensity from 100 rpm to 7 rpm and even ceasing mixing all together. This was true both for primary solids and glycerol. In addition propionate content was high under both high and low intensity, and adding glycerol also increased the fraction of primary solids that formed propionic acid instead of acetic acid. Increasing the SRT from 2 to 4 days increased the VFA production about 12% on average. In order to investigate the effect of glycerol on EBPR process efficiency two identical A2/O systems were monitored for 3 months. Experimental results suggested that glycerol addition could increase the P removal efficiency significantly. Adding glycerol to the prefermenter rather than the anaerobic zone resulted in a lower effluent soluble ortho phosphorus (SOP) (0.4 mg-P/L vs. 0.6 mg-P/L) but the difference was apparently statistically significant. Future experimentation should be done to determine if this effect is consistent, especially in carbon poor wastewaters. Also it would be desirable to conduct a longer pilot study or a full scale study to determine if this improvement in effluent SOP remains true over a range of temperature and changing influent conditions.
Show less - Date Issued
- 2015
- Identifier
- CFE0006310, ucf:51612
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006310
- Title
- Design of High-Efficiency Rare-Earth Permanent Magnet Synchronous Motor and Drive System.
- Creator
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Liu, Hanzhou, Wu, Thomas, Batarseh, Issa, Haralambous, Michael, Lin, Mingjie, Chow, Louis, University of Central Florida
- Abstract / Description
-
Utilization of renewable energy has become the future trend in the trucking industry. Electrical power generated from renewable energy can replace part of the fuel usage. There is usually limited space for storing on-board battery. Thus, to better utilize the battery power, it becomes critical to have an efficient energy conversion device that can transfer energy from battery to amenities such as air conditioner, microwave, TV, mini refrigerator, etc. In this dissertation, a designed...
Show moreUtilization of renewable energy has become the future trend in the trucking industry. Electrical power generated from renewable energy can replace part of the fuel usage. There is usually limited space for storing on-board battery. Thus, to better utilize the battery power, it becomes critical to have an efficient energy conversion device that can transfer energy from battery to amenities such as air conditioner, microwave, TV, mini refrigerator, etc. In this dissertation, a designed permanent magnet synchronous motor (PMSM) can be such energy conversion device for an electric Auxiliary Power Unit (APU) application, which will have a desired output power of 2 kW at 2krpm, and maintain an efficiency greater than 90%. The design calls for good performance over a speed range of 1.5 krpm to 2.5 krpm. The current air conditioning system for automobile works only by (")on(") or (")off(") mode. For the heat mode, that means it is on with heat once the cabin temperature drops down to a level and off if the temperature rises back above that level. For the cool mode, that means it is on with cold air once the cabin temperature rises above a level, and off if the temperature drops back to that level. This is because the motor does not have the speed control functionality according to the temperature variation and people in the cabin do not feel much comfortable for that temperature change periodically as well as the inefficient energy consumption. With our novel technology, the designed motor can adjust its speed through the embedded system of our novel DC to AC inverter to provide a variable load. For example, with high efficiency, the fully charged battery sets (48 volts) can supply the electrical power and cooling to the cabin forabout 10 hours without recharging using the main engine.Copper loss is the most significant part of all the losses in low speed electric machines. Reducing the copper loss is the key to build highly efficient machine. We use copper wires with the current density lower than traditional design which result in large cross section of the wire and thus reduce the copper loss and improve the efficiency. This also makes thermal management easier and reduces the need to use active cooling methodologies (such as fan, liquid cooling or spray cooling); and hence the overall power density of the whole system (including cooling devices) will not decease much. In traditional machine design, the torque angle is designed to be in the rangeof 15 to 30 degrees at the rated power and speed. In our high efficiency motor design, we propose to use much lower torque angle of 2 to 15 degrees at the rated power and speed. Such design caneffectively increase the overload power handling capability and efficiency. Besides, small torque angle will result in large airgap size and increased thickness of the permanent magnets. Large airgap helps to reduce the windage loss of the machine and generates a lot less mechanical noise based on our design experience. Increased thickness of the permanent magnets helps to avoid thedemagnetization.As the technology of advanced micro-controller develops, fast response power electronic devices can be used in the motor controller. A novel design of DC to AC inverter with the fieldoriented control scheme and sliding mode observer algorithm for driving the designed motor is developed. The inverter has the capability of driving the motor with its output power at 2 kW.
Show less - Date Issued
- 2015
- Identifier
- CFE0006224, ucf:51064
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006224
- Title
- Manufacturing of Single Solid Oxide Fuel Cells.
- Creator
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Torres-Caceres, Jonathan, Orlovskaya, Nina, Xu, Yunjun, Das, Tuhin, University of Central Florida
- Abstract / Description
-
Solid oxide fuel cells (SOFCs) are devices that convert chemical energy into electrical energy and have the potential to become a reliable renewable energy source that can be used on a large scale. SOFCs have 3 main components; the electrolyte, the anode, and the cathode. Typically, SOFCs work by reducing oxygen at the cathode into O2- ions which are then transported via the electrolyte to the anode to combine with a fuel such as hydrogen to produce electricity. Research into better materials...
Show moreSolid oxide fuel cells (SOFCs) are devices that convert chemical energy into electrical energy and have the potential to become a reliable renewable energy source that can be used on a large scale. SOFCs have 3 main components; the electrolyte, the anode, and the cathode. Typically, SOFCs work by reducing oxygen at the cathode into O2- ions which are then transported via the electrolyte to the anode to combine with a fuel such as hydrogen to produce electricity. Research into better materials and manufacturing methods is necessary to reduce costs and improve efficiency to make the technology commercially viable.The goal of the research is to optimize and simplify the production of single SOFCs using high performance ceramics. This includes the use of 8mol% Y2O3-ZrO2 (YSZ) and 10mol% Sc2O3-1mol%CeO2-ZrO2 (SCSZ) layered electrolytes which purport higher conductivity than traditional pure YSZ electrolytes. Prior to printing the electrodes onto the electrolyte, the cathode side of the electrolyte was coated with 20mol% Gd2O3-CeO2 (GDC). The GDC coating prevents the formation of a nonconductive La2Zr2O7 pyrochlore layer, which forms due to the interdiffusion of the YSZ electrolyte ceramic and the (La0.6Sr0.4)0.995Fe0.8Co0.2O3 (LSCF) cathode ceramic during sintering. The GDC layer was deposited by spin coating a suspension of 10wt% GDC in ethanol onto the electrolyte. Variation of parameters such as time, speed, and ramp rate were tested. Deposition of the electrodes onto the electrolyte surface was done by screen printing. Ink was produced using a three roll mill from a mixture of ceramic electrode powder, terpineol, and a pore former. The pore former was selected based on its ability to form a uniform well-connected pore matrix within the anode samples that were pressed and sintered. Ink development involved the production of different ratios of powder-to-terpineol inks to vary the viscosity. The different inks were used to print electrodes onto the electrolytes to gauge print quality and consistency. Cells were produced with varying numbers of layers of prints to achieve a desirable thickness. Finally, the densification behaviors of the major materials used to produce the single cells were studied to determine the temperatures at which each component needs to be sintered to achieve the desired density and to determine the order of electrode application, so as to avoid over-densification of the electrodes. Complete cells were tested at the National Energy Technology Laboratory in Morgantown, WV. Cells were tested in a custom-built test stand under constant voltage at 800(&)deg;C with 3% humidified hydrogen as the fuel. Both voltage-current response and impedance spectroscopy tests were conducted after initial startup and after 20 hours of operation. Impedance tests were performed at open circuit voltage and under varying loads in order to analyze the sources of resistance within the cell. A general increase in impedance was found after the 20h operation. Scanning electron micrographs of the cell microstructures found delamination and other defects which reduce performance. Suggestions for eradicating these issues and improving performance have been made.
Show less - Date Issued
- 2013
- Identifier
- CFE0004946, ucf:49641
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004946
- Title
- Energy Harvesting toward the Vibration Reduction of Turbomachinery Blades via Resonance Frequency Detuning.
- Creator
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Hynds, Taylor, Kauffman, Jeffrey, Das, Tuhin, Raghavan, Seetha, University of Central Florida
- Abstract / Description
-
Piezoelectric-based energy harvesting devices provide an attractive approach to powering remote devices as ambient mechanical energy from vibrations is converted to electrical energy. These devices have numerous potential applications, including actuation, sensing, structural health monitoring, and vibration control -- the latter of which is of particular interest here. This work seeks to develop an understanding of energy harvesting behavior within the framework of a semi-active technique...
Show morePiezoelectric-based energy harvesting devices provide an attractive approach to powering remote devices as ambient mechanical energy from vibrations is converted to electrical energy. These devices have numerous potential applications, including actuation, sensing, structural health monitoring, and vibration control -- the latter of which is of particular interest here. This work seeks to develop an understanding of energy harvesting behavior within the framework of a semi-active technique for reducing turbomachinery blade vibrations, namely resonance frequency detuning. In contrast with the bulk of energy harvesting research, this effort is not focused on maximizing the power output of the system, but rather providing the low power levels required by resonance frequency detuning. The demands of this technique dictate that harvesting conditions will be far from optimal, requiring that many common assumptions in conventional energy harvesting research be relaxed.Resonance frequency detuning has been proposed as a result of recent advances in turbomachinery blade design that have, while improving their overall efficiency, led to significantly reduced damping and thus large vibratory stresses. This technique uses piezoelectric materials to control the stiffness, and thus resonance frequency, of a blade as the excitation frequency sweeps through resonance. By detuning a structure's resonance frequency from that of the excitation, the overall peak response can be reduced, delaying high cycle fatigue and extending the lifetime of a blade. Additional benefits include reduced weight, drag, and noise levels as reduced vibratory stresses allow for increasingly light blade construction.As resonance frequency detuning is most effective when the stiffness states are well separated, it is necessary to harvested at nominally open- and short-circuit states, corresponding to the largest separation in stiffness states. This presents a problem from a harvesting standpoint however, as open- and short-circuit correspond to zero charge displacement and zero voltage, respectively, and thus there is no energy flow. It is, then, desirable to operate as near these conditions as possible while still harvesting sufficient energy to provide the power for state-switching. In this research a metric is developed to study the relationship between harvested power and structural stiffness, and a key result is that appreciable energy can be harvested far from the usual optimal conditions in a typical energy harvesting approach. Indeed, sufficient energy is available to power the on-blade control while essentially maintaining the desired stiffness states for detuning. Furthermore, it is shown that the optimal switch in the control law for resonance frequency detuning may be triggered by a threshold harvested power, requiring minimal on-blade processing. This is an attractive idea for implementing a vibration control system on-blade, as size limitations encourage removing the need for additional sensing and signal processing hardware.
Show less - Date Issued
- 2015
- Identifier
- CFE0005811, ucf:50039
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005811
- Title
- A Lab-Scale Experimental Framework for Studying the Phenomenon of Autorotation.
- Creator
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Rimkus, Sigitas, Das, Tuhin, Xu, Yunjun, Simaan, Marwan, University of Central Florida
- Abstract / Description
-
While wind energy has emerged as a popular source of renewable energy, the traditional wind turbine has an inherent limitation, namely that it only generates power in the presence of sufficiently high and consistent wind speeds. As a result, wind farms are typically built in areas with a high probability of the required wind speeds, which are geographically sparse. One way of overcoming this drawback is to tap into the energy available in winds at high altitudes which are not only consistent...
Show moreWhile wind energy has emerged as a popular source of renewable energy, the traditional wind turbine has an inherent limitation, namely that it only generates power in the presence of sufficiently high and consistent wind speeds. As a result, wind farms are typically built in areas with a high probability of the required wind speeds, which are geographically sparse. One way of overcoming this drawback is to tap into the energy available in winds at high altitudes which are not only consistent and of high magnitude, but also globally pervasive. An airborne wind energy device based upon the phenomenon of autorotation could potentially be used to exploit the abundance of wind of energy present at high altitudes.The work in this thesis first presents our study of a tethered-airfoil system as a candidate airborne wind energy (AWE) system. A mathematical model was used to show the feasibility of energy capture and the stability of the device in a wind field. Subsequently, the research identified the principle of autorotation to be better suited for high altitude energy harvesting. To this end, the thesis first presents a theoretical basis of the principle of autorotation, which is developed from existing models in literature. The model was adapted to predict aerodynamic conditions when used for harvesting energy. Encouraging simulation results prompted the main emphasis of this thesis, namely design of an experimental framework to corroborate the theory. Several experiments were devised to determine basic performance characteristics of an autogyro rotor and the data from each experiment is presented. A lab-scale experimental setup was developed as part of this thesis. The setup, consisting of a flapping-blade autogyro rotor and sensors, was used to acquire preliminary aerodynamic performance data. It is envisioned that refinements to this setup will ultimately provide a means of directly comparing analytical and experimental data. In this regard, we provide conclusions and make comments on improvements for future experiments.
Show less - Date Issued
- 2014
- Identifier
- CFE0005239, ucf:50593
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005239
- Title
- Investigating the Influence of the Built Environment on Energy-Saving Behaviors.
- Creator
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Sellers, Brittany, Jentsch, Florian, Smither, Janan, Sims, Valerie, Fiore, Stephen, University of Central Florida
- Abstract / Description
-
This dissertation addresses a gap in the existing sustainability behavior research, by integrating research from the social sciences about environmental attitudes and knowledge with approaches from engineering regarding the characteristics of the built environment. Specifically, this dissertation explores the role of both environmental knowledge and design features within the built environment on building occupants' energy behaviors throughout the course of an environmental conservation...
Show moreThis dissertation addresses a gap in the existing sustainability behavior research, by integrating research from the social sciences about environmental attitudes and knowledge with approaches from engineering regarding the characteristics of the built environment. Specifically, this dissertation explores the role of both environmental knowledge and design features within the built environment on building occupants' energy behaviors throughout the course of an environmental conservation campaign. Data were collected from 240 dormitory residents using a multi-phase questionnaire approach to study these factors and their combined impact within the context of environmental sustainability practices on UCF's campus. The results from a series of correlational and multiple regression analyses indicate that both the design components of the built environment and the attitudes held by individuals within that environment have a significant positive influence on behaviors. Furthermore, these findings indicated that this effect increases significantly when the two factors work together. Finally, the results show that pro- environmental attitudes and behaviors can be successfully targeted through a cue-based energy conservation campaign. By addressing a gap in the extant Human Factors research about the relationship between attitudinal factors and the built environment, this dissertation provides a unique contribution to the field and points the way towards development of promising solutions for encouraging sustainable behaviors.
Show less - Date Issued
- 2016
- Identifier
- CFE0006500, ucf:51387
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006500
- Title
- A Holistic Analysis of the Long-Term Challenges (&) Potential Benefits of the Green Roof, Solar PV Roofing, and GRIPV Roofing Markets in Orlando, Florida.
- Creator
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Kelly, Carolina, Tatari, Omer, Oloufa, Amr, Mayo, Talea, Zheng, Qipeng, University of Central Florida
- Abstract / Description
-
Green roofs and roof-mounted solar PV arrays have a wide range of environmental and economic benefits, including significantly longer roof lifetimes, reductions in urban runoff, mitigation of the urban heat island (UHI) effect, reduced electricity demand and energy dependence, and/or reduced emissions of greenhouse gases (GHGs) and other harmful pollutants from the electricity generation sector. Consequently, green roofs and solar panels have both become increasingly popular worldwide, and...
Show moreGreen roofs and roof-mounted solar PV arrays have a wide range of environmental and economic benefits, including significantly longer roof lifetimes, reductions in urban runoff, mitigation of the urban heat island (UHI) effect, reduced electricity demand and energy dependence, and/or reduced emissions of greenhouse gases (GHGs) and other harmful pollutants from the electricity generation sector. Consequently, green roofs and solar panels have both become increasingly popular worldwide, and promising new research has emerged for their potential combination in Green Roof Integrated Photovoltaic (GRIPV) roofing applications. However, due to policy resistance, these alternatives still have marginal market shares in the U.S., while GRIPV research and development is still severely limited today. As a result, these options are not yet sufficiently widespread in the United States as to realize their full potential, particularly due to a variety of policy resistance effects with respect to each specific alternative. The steps in the System Dynamics (SD) methodology to be used in this study are summarized as follows. First, based on a comprehensive review of relevant literature, a causal loop diagram (CLD) will be drawn to provide a conceptual illustration of the modeled system. Second, based on the feedback relationships observed in this CLD, a stock-flow diagram (SFD) will be developed to form a quantitative model. Third, the modeled SFD will be tested thoroughly to ensure its structural and behavioral validity with respect to the modeled system in reality using whatever real world data is available. Fourth, different policy scenarios will be simulated within the model to evaluate their long-term effectiveness. Fifth, uncertainty analyses will be performed to evaluate the inherent uncertainties associated with the analyses in this study. Finally, the results observed for the analyses in this study and possible future research steps will be discussed and compared as appropriate.
Show less - Date Issued
- 2018
- Identifier
- CFE0007406, ucf:52741
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007406
- Title
- The Effect of Morphology on Reflectance in Silicon Nanowires Grown by Electroless Etching.
- Creator
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Velez, Victor, Sundaram, Kalpathy, Kapoor, Vikram, Yuan, Jiann-Shiun, Abdolvand, Reza, Kar, Aravinda, University of Central Florida
- Abstract / Description
-
The strong light trapping properties of Silicon Nanowires have attracted much interest in the past few years for the conversion of sun energy into conventional electricity. Studies have been completed for many researchers to reduce the cost of fabrication and reflectance of solar light in these nanostructures to make a cheaper and more efficient solar cell technology by using less equipment for fabrication and employing different materials and solution concentrations. Silver, a conducting and...
Show moreThe strong light trapping properties of Silicon Nanowires have attracted much interest in the past few years for the conversion of sun energy into conventional electricity. Studies have been completed for many researchers to reduce the cost of fabrication and reflectance of solar light in these nanostructures to make a cheaper and more efficient solar cell technology by using less equipment for fabrication and employing different materials and solution concentrations. Silver, a conducting and stable metal is used these days as a precursor to react with silicon and then form the nanowires. Its adequate selection of solution concentration for a size of silicon substrate and the treatment for post-cleaning of silver dendrites make it a viable method among the others. It is an aim of this research to obtain significant low reflectance across the visible solar light range. Detailed concentration, fabrication and reflectance studies is carried out on silicon wafer in order to expand knowledge and understanding.In this study, electroless etching technique has been used as the growth mechanism of SiNWs at room temperature. Optimum ratios of solution concentration and duration for different sizes of exposed area to grow tall silicon nanowires derived from experimentation are presented. Surface imaging of the structures and dimension of length and diameter have been determined by Scanner Electron Microscopy (SEM) and the reflectance in the optical range in silicon nanowires has been make using UV-Visible Spectrophotometer.
Show less - Date Issued
- 2017
- Identifier
- CFE0006815, ucf:51807
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006815
- Title
- Finding Consensus Energy Folding Landscapes Between RNA Sequences.
- Creator
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Burbridge, Joshua, Zhang, Shaojie, Hu, Haiyan, Jha, Sumit, University of Central Florida
- Abstract / Description
-
In molecular biology, the secondary structure of a ribonucleic acid (RNA) molecule is closely related to its biological function. One problem in structural bioinformatics is to determine the two- and three-dimensional structure of RNA using only sequencing information, which can be obtained at low cost. This entails designing sophisticated algorithms to simulate the process of RNA folding using detailed sets of thermodynamic parameters. The set of all chemically feasible structures an RNA...
Show moreIn molecular biology, the secondary structure of a ribonucleic acid (RNA) molecule is closely related to its biological function. One problem in structural bioinformatics is to determine the two- and three-dimensional structure of RNA using only sequencing information, which can be obtained at low cost. This entails designing sophisticated algorithms to simulate the process of RNA folding using detailed sets of thermodynamic parameters. The set of all chemically feasible structures an RNA molecule can assume, as well as the energy associated with each structure, is called its energy folding landscape. This research focuses on defining and solving the problem of finding the consensus landscape between multiple RNA molecules. Specifically, we discuss how this problem is equivalent to the problem of Balanced Global Network Alignment, and what effect a solution to this problem would have on our understanding of RNA.Because this problem is known to be NP-hard, we instead define an approximate consensus on a landscape of reduced size, which dramatically reduces the searching space associated with the problem. We use the program RNASLOpt to enumerate all stable local optimal secondary structures in multiple landscapes within a certain energy and stability range of the minimum free energy (MFE) structure. We then encode these using an extended structural alphabet and perform sequence alignment using a structural substitution matrix to find and rank the best matches between the sets based on stability, energy, and structural distance. We apply this method to twenty landscapes from four sets of riboswitches from Bacillus subtillis in order to predict their native (")on(") and (")off(") structures. We find that this method significantly reduces the size of the list of candidate structures, as well as increasing the ranking of previously obscure secondary structures, resulting in more accurate predictions overall. Advances in the field of structural bioinformatics can help elucidate the underlying mechanisms of many genetic diseases.
Show less - Date Issued
- 2015
- Identifier
- CFE0006210, ucf:51109
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006210
- Title
- The United Nations and the bomb: A radio discussion.
- Creator
-
Finletter, Thomas Knight, Shils, Edward, Urey, Harold Clayton
- Date Issued
- 1946
- Identifier
- 369646, CFDT369646, ucf:5459
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/FCLA/DT/369646
- Title
- TWO-PHOTON 3D OPTICAL DATA STORAGE VIA FLUORESCENCE MODULATION OF FLUORENE DYES BY PHOTOCHROMIC DIARYLETHENES.
- Creator
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Corredor, Claudia, Belfield, Kevin D., University of Central Florida
- Abstract / Description
-
Three-dimensional (3D) optical data storage based on two-photon processes provides highly confined excitation in a recording medium and a mechanism for writing and reading data with less cross talk between multiple memory layers, due to the quadratic dependence of two photon absorption (2PA) on the incident light intensity. The capacity for highly confined excitation and intrinsic 3D resolution affords immense information storage capacity (up to 1012 bits/cm3). Recently, the use of...
Show moreThree-dimensional (3D) optical data storage based on two-photon processes provides highly confined excitation in a recording medium and a mechanism for writing and reading data with less cross talk between multiple memory layers, due to the quadratic dependence of two photon absorption (2PA) on the incident light intensity. The capacity for highly confined excitation and intrinsic 3D resolution affords immense information storage capacity (up to 1012 bits/cm3). Recently, the use of photochromic materials for 3D memory has received intense interest because of several major advantages over current optical systems, including their erasable/rewritable capability, high resolution, and high sensitivity. This work demonstrates a novel two-photon 3D optical storage system based on the modulation of the fluorescence emission of a highly efficient two-photon absorbing fluorescent dye (fluorene derivative) and a photochromic compound (diarylethene). The feasibility of using efficient intermolecular Förster Resonance Energy Transfer (RET) from the non-covalently linked two-photon absorbing fluorescent fluorene derivative to the photochromic diarylethene as a novel read-out method in a two-photon optical data storage system was explored. For the purpose of the development of this novel two-photon 3D optical storage system, linear and two-photon spectroscopic characterization of commercial diarylethenes in solution and in a polymer film and evidence of their cyclization (O→C) and cycloreversion (C→O) reactions induced by two-photon excitation were undertaken. For the development of a readout method, Resonance Energy Transfer (RET) from twophoton absorbing fluorene derivatives to photochromic compounds was investigated under one and two-photon excitation. The Förster's distances and critical acceptor concentrations were determined for non-bound donor-acceptor pairs in homogeneous molecular ensembles. To the best of my knowledge, modulation of the two-photon fluorescence emission of a dye by a photochromic diarylethene has not been reported as a mechanism to read the recorded information in a 3D optical data storage system. This system was demonstrated to be highly stable and suitable for recording data in thick storage media. The proposed RET-based readout method proved to be non-destructive (exhibiting a loss of the initial fluorescence emission less than 20% of the initial emission after 10,000 readout cycles). Potential application of this system in a rewritable-erasable optical data storage system was proved. As part of the strategy for the development of diarylethenes optimized for 3D optical data storage, derivatives containing π-conjugated fluorene molecules were synthesized and characterized. The final part of this reasearch demonstrated the photostability of fluorine derivatives showing strong molecular polarizability and high fluorescence quantum yields. These compounds are quite promising for application in RET-based two-photon 3D optical data storage. Hence, the photostability of these fluorene derivatives is a key parameter to establish, and facilitates their full utility in critical applications.
Show less - Date Issued
- 2007
- Identifier
- CFE0001662, ucf:47210
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001662
- Title
- MICROSTRUCTURAL AND MECHANICAL CHARACTERIZATION OF AL-AL2O3 NANOCOMPOSITES SYNTHESIZED BY HIGH-ENERGY MILLING.
- Creator
-
Prabhu, Balaji, Challapalli, Suryanarayana, University of Central Florida
- Abstract / Description
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The twin objectives of the investigation were (i) to synthesize Al/Al2O3 metal matrix composites (MMCs) with uniform distribution of the Al2O3 reinforcement in the Al matrix and (ii) to evaluate the effect of volume fraction and size of the reinforcement on the mechanical behavior of MMCs. This was achieved by successful synthesis of Al-Al2O3 MMCs with volume fractions of 5, 10, 20, 30, and 50%, and particle sizes of 50 nm, 150 nm, and 5 µm of Al2O3 synthesized from blended component...
Show moreThe twin objectives of the investigation were (i) to synthesize Al/Al2O3 metal matrix composites (MMCs) with uniform distribution of the Al2O3 reinforcement in the Al matrix and (ii) to evaluate the effect of volume fraction and size of the reinforcement on the mechanical behavior of MMCs. This was achieved by successful synthesis of Al-Al2O3 MMCs with volume fractions of 5, 10, 20, 30, and 50%, and particle sizes of 50 nm, 150 nm, and 5 µm of Al2O3 synthesized from blended component powders by a high-energy milling technique. A uniform distribution of the Al2O3 reinforcement in the Al matrix was successfully obtained after milling the powders for a period of 20 h with a ball-to-powder weight ratio of 10:1 in a SPEX mill. The uniform distribution of Al2O3 in the Al matrix was confirmed by characterizing these nanocomposite powders by scanning electron microscopy and X-ray mapping. The energy dispersive spectroscopy and X-ray diffraction techniques were employed to determine the composition and phase analysis, respectively. The milled powders were then consolidated for subsequent mechanical characterization by (i) magnetic pulse compaction (MPC) (ii) hot-isostatic pressing (HIP), (iii) vaccum hot pressing (VHP), and (iv) a combination of vaccum hot pressing and hot-isostatic pressing (VHP+HIP). However, successful consolidation of the powders to near-full density was achieved only through VHP+HIP for the 5 and 10 vol. % Al2O3 samples with 50 nm and 150 nm particle sizes. The fully dense samples were then subjected to mechanical characterization by compression testing and nanoindentation techniques. The strength and elastic modulus values obtained from compression testing showed an increase with increasing volume fraction and decreasing particle size of the reinforcement. The nanoindentation results were, however, contradictory, and the presence of residual stresses in the samples was attributed as the cause for the deviation in values.
Show less - Date Issued
- 2005
- Identifier
- CFE0000727, ucf:46602
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000727
- Title
- OPTIMAL SINTERING TEMPERATURE OF CERIA-DOPED SCANDIA STABILIZED ZIRCONIA FOR USE IN SOLID OXIDE FUEL CELLS.
- Creator
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Assuncao, Amanda K, Orlovskaya, Nina, University of Central Florida
- Abstract / Description
-
Carbon emissions are known to cause decay of the Ozone layer in addition to creating pollutant, poisonous air. This has become a growing concern among scientists and engineers across the globe; if this issue is not addressed, it is likely that the Earth will suffer catastrophic consequences. One of the main culprits of these harmful carbon emissions is fuel combustion. Between vehicles, power plants, airplanes, and ships, the world consumes an extraordinary amount of oil and fuel which all...
Show moreCarbon emissions are known to cause decay of the Ozone layer in addition to creating pollutant, poisonous air. This has become a growing concern among scientists and engineers across the globe; if this issue is not addressed, it is likely that the Earth will suffer catastrophic consequences. One of the main culprits of these harmful carbon emissions is fuel combustion. Between vehicles, power plants, airplanes, and ships, the world consumes an extraordinary amount of oil and fuel which all contributes to the emissions problem. Therefore, it is crucial to develop alternative energy sources that minimize the impact on the environment. One such technology that is currently being researched, is the Solid Oxide Fuel Cell (SOFC). This is a relatively simple device that converts chemical energy into electrical energy with no harmful emissions. For these devices to work properly, they require an electrolyte material that has high ionic conductivity with good phase stability at a variety of temperatures. The research presented in this study will concentrate intensively on just one of the many candidates for SOFC electrolytes. 1 mol% CeO2 - 10 mol% Sc2O3 - 89 mol% ZrO2 manufactured by Treibacher Industries was analyzed to better understand its sintering properties, phase stability, and molecular structure. Sintering was performed at temperatures ranging from 900oC to 1600oC and the shrinkage, density and porosity were examined for each temperature. Raman Spectroscopy and X-Ray Powder Diffraction were also conducted for comparison with other known compositions to see if the powder undergoes any phase transitions or instability.
Show less - Date Issued
- 2018
- Identifier
- CFH2000408, ucf:45894
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000408
- Title
- CHARACTERISTICS OF THE ADULT FEMALE ENDURANCE RUNNER: A SURVEY.
- Creator
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Gabriel, Stephanie F, Rothschild, Carey, University of Central Florida
- Abstract / Description
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Objective: This study investigated the behaviors and characteristics of the adult female endurance runner and potential components of the female athlete triad (FAT). The FAT consists of three components that are interrelated: low energy availability, menstrual dysfunction, and low bone mineral density. Low energy availability may occur with or without disordered eating. Reproduction becomes non-essential leading to irregular menstrual cycles. A reduction in estrogen levels may contribute to...
Show moreObjective: This study investigated the behaviors and characteristics of the adult female endurance runner and potential components of the female athlete triad (FAT). The FAT consists of three components that are interrelated: low energy availability, menstrual dysfunction, and low bone mineral density. Low energy availability may occur with or without disordered eating. Reproduction becomes non-essential leading to irregular menstrual cycles. A reduction in estrogen levels may contribute to low bone mineral density which may lead to stress fractures. Research investigating the FAT has primarily focused on adolescent and young adult females. Adult females training for endurance events may also be at risk for the FAT. Method: A survey was constructed and distributed to females in a local half-marathon and marathon training group in Central Florida. The data was collected at one point in time and no additional follow-up was required. The survey aimed to identify specific behaviors and characteristics related to components of the FAT and determine the potential prevalence in a small sample of female endurance athletes aged 18 and older. Results: 72 females with a mean age of 40.92(± 9.61) years completed the survey. Subjects had an average height of 163.60(±6.41) cm, weighed an average of 62.24(±10.05) kg and had 10 years of running experience. Conclusion: Adult female endurance runners demonstrate behaviors and characteristics that may be indicative of the FAT. Participants demonstrated signs of inadvertent or intentional low energy availability. These characteristics can be due to either body dissatisfaction or wanting to increase performance.
Show less - Date Issued
- 2017
- Identifier
- CFH2000173, ucf:45926
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000173
- Title
- EFFECTS OF CAFFEINATED ENERGY DRINK AND ALCOHOL USAGE ON PERCEIVED STRESS AND BURNOUT IN UNDERGRADUATE STUDENTS.
- Creator
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Patel, Arjun, Webster, Danielle, University of Central Florida
- Abstract / Description
-
Caffeinated energy beverages (CEDs) are a growing supplement being consumed by a large number of young adults aged 18 to 24 years of age. As these CEDs contain nutritional supplements, they are not classified the same way other beverages such as sodas are and they can thus bypass regulation by the Food and Drug Administration. Without regulation by this governing body, it is important to understand how these supplements may be affecting their target population. In this study, students from a...
Show moreCaffeinated energy beverages (CEDs) are a growing supplement being consumed by a large number of young adults aged 18 to 24 years of age. As these CEDs contain nutritional supplements, they are not classified the same way other beverages such as sodas are and they can thus bypass regulation by the Food and Drug Administration. Without regulation by this governing body, it is important to understand how these supplements may be affecting their target population. In this study, students from a large university were recruited in order to determine patterns of CED usage as well as how CED usage may affect perceived stress and burnout. Alcohol usage, another type of beverage commonly consumed in this population, was also assayed in this group in order to determine how perceived stress and burnout are affected. The study was case-control in nature, as regular users of CEDs were compared against students who were not regular consumers. From the data, no major relationships could be identified in regards to perceived stress, burnout, and CED usage. However, extracurricular activity was found to be somewhat predictive of CED usage while alcohol usage was found to be negatively correlated with perceived stress.
Show less - Date Issued
- 2015
- Identifier
- CFH0004787, ucf:45333
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004787
- Title
- DESIGN AND EXPERIMENTAL STUDY OF AN INTEGRATED VAPOR CHAMBER – THERMAL ENERGY STORAGE SYSTEM.
- Creator
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Kota, Krishna, CHOW, LOUIS, University of Central Florida
- Abstract / Description
-
Future defense, aerospace and automotive technologies involve electronic systems that release high pulsed waste heat like during high power microwave and laser diode applications in tactical and combat aircraft, and electrical and electronic systems in hybrid electric vehicles, which will require the development of an efficient thermal management system. A key design issue is the need for fast charging so as not to overheat the key components. The goal of this work is to study the fabrication...
Show moreFuture defense, aerospace and automotive technologies involve electronic systems that release high pulsed waste heat like during high power microwave and laser diode applications in tactical and combat aircraft, and electrical and electronic systems in hybrid electric vehicles, which will require the development of an efficient thermal management system. A key design issue is the need for fast charging so as not to overheat the key components. The goal of this work is to study the fabrication and technology implementation feasibility of a novel high energy storage, high heat flux passive heat sink. Key focus is to verify by theory and experiments, the practicability of using phase change materials as a temporary storage of waste heat for heat sink applications. The reason for storing the high heat fluxes temporarily is to be able to reject the heat at the average level when the heat source is off. Accordingly, a concept of a dual latent heat sink intended for moderate to low thermal duty cycle electronic heat sink applications is presented. This heat sink design combines the features of a vapor chamber with rapid thermal energy storage employing graphite foam inside the heat storage facility along with phase change materials and is attractive owing to its passive operation unlike some of the current thermal management techniques for cooling of electronics employing forced air circulation or external heat exchangers. In addition to the concept, end-application dependent criteria to select an optimized design for this dual latent heat sink are presented. A thermal resistance concept based design tool/model has been developed to analyze and optimize the design for experiments. The model showed that it is possible to have a dual latent heat sink design capable of handling 7 MJ of thermal load at a heat flux of 500 W/cm2 (over an area of 100 cm2) with a volume of 0.072 m3 and weighing about 57.5 kg. It was also found that with such high heat flux absorption capability, the proposed conceptual design could have a vapor-to-condenser temperature difference of less than 10 0C with a volume storage density of 97 MJ/m3 and a mass storage density of 0.122 MJ/kg. The effectiveness of this heat sink depends on the rapidness of the heat storage facility in the design during the pulse heat generation period of the duty cycle. Heat storage in this heat sink involves transient simultaneous laminar film condensation of vapor and melting of an encapsulated phase change material in graphite foam. Therefore, this conjugate heat transfer problem including the wall inertia effect is numerically analyzed and the effectiveness of the heat storage mechanism of the heat sink is verified. An effective heat capacity formulation is employed for modeling the phase change problem and is solved using finite element method. The results of the developed model showed that the concept is effective in preventing undue temperature rise of the heat source. Experiments are performed to investigate the fabrication and implementation feasibility and heat transfer performance for validating the objectives of the design i.e., to show that the VCTES heat sink is practicable and using PCM helps in arresting the vapor temperature rise in the heat sink. For this purpose, a prototype version of the VCTES heat sink is fabricated and tested for thermal performance. The volume foot-print of the vapor chamber is about 6"X5"X2.5". A custom fabricated thermal energy storage setup is incorporated inside this vapor chamber. A heat flux of 40 W/cm2 is applied at the source as a pulse and convection cooling is used on the condenser surface. Experiments are done with and without using PCM in the thermal energy storage setup. It is found that using PCM as a second latent system in the setup helps in lowering the undue temperature rise of the heat sink system. It is also found that the thermal resistance between the vapor chamber and the thermal energy storage setup, the pool boiling resistance at the heat source in the vapor chamber, the condenser resistance during heat discharging were key parameters that affect the thermal performance. Some suggestions for future improvements in the design to ease its implementation and enhance the heat transfer of this novel heat sink are also presented.
Show less - Date Issued
- 2008
- Identifier
- CFE0002332, ucf:47802
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002332
- Title
- EVALUATION OF CLIMATIC AND ECOHYDROLOGICAL EFFECTS ON LONGWAVE RADIATION AND EVAPOTRANSPIRATION.
- Creator
-
Rizou, Maria, Nnadi, Fidelia, University of Central Florida
- Abstract / Description
-
Modern tools, nontraditional datasets and a better understanding of the interaction between climate and ecohydrology are continuously being developed as today's society is in critical need for improving water management, predicting hydrometeorological hazards and forecasting future climate. In particular, the study of the intra- and inter-annual variations in grass productivity and evapotranspiration caused by variations in precipitation/soil moisture and other biophysical factors is of...
Show moreModern tools, nontraditional datasets and a better understanding of the interaction between climate and ecohydrology are continuously being developed as today's society is in critical need for improving water management, predicting hydrometeorological hazards and forecasting future climate. In particular, the study of the intra- and inter-annual variations in grass productivity and evapotranspiration caused by variations in precipitation/soil moisture and other biophysical factors is of great significance due to their relation to future climatic changes. The research presented here falls in three parts. In the first part of the dissertation, a land use adaptable model, based on the superposition of the temperature and water vapor pressure effects, is proposed for the effective clear sky emissivity. Ground radiometer and meteorological data, applicable in the subtropical climate of Saint Johns River Water Management District, Florida, were utilized for the model development over the spring season of 2004. The performance of this model was systematically evaluated by pertinent comparisons with previously established models using data over various land covers. The second part of the thesis investigates the dynamics of evapotranspiration with respect to its significant environmental and biological controls over an unmanaged bahia grassland. Eddy correlation measurements were carried out at a flux tower in Central Florida over the annual course of 2004. The main focus was on the sensitivity of the water vapor flux to wetness variables, namely the volumetric soil water content and the current precipitation index. It was shown that the time scales involved with the dynamics of evapotranspiration were on the order of six days, suggesting that depletion of the soil moisture was mostly responsible for the temporal fluctuations in evapotranspiration. Finally, simple models for the Priestley-Taylor factor were employed in terms of water availability, and the modeled results closely matched the eddy covariance flux values on daily time scale during all moisture conditions. In the third part of this work, the partitioning between latent and sensible heat fluxes was systematically examined with respect to biophysical factors. It was found that the seasonal variations in leaf area index, soil water content and net radiation were reflected in a strong seasonal pattern of the energy balance. Calculations of the bulk parameters, namely Priestley-Taylor parameter and decoupling coefficient, indicated that evapotranspiration of this grassland was controlled by water supply limitations and surface conductance. At an annual basis, the cumulative evapotranspiration was 59 percent of the precipitation received at the site. The results of this research complemented with other studies will promote better understanding of land-atmosphere interactions, accurate parameterizations of hydroclimatic models, and assessment of climate impact of grassland ecosystems.
Show less - Date Issued
- 2008
- Identifier
- CFE0002279, ucf:47851
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002279
- Title
- Soft-Error Resilience Framework For Reliable and Energy-Efficient CMOS Logic and Spintronic Memory Architectures.
- Creator
-
Alghareb, Faris, DeMara, Ronald, Lin, Mingjie, Zou, Changchun, Jha, Sumit Kumar, Song, Zixia, University of Central Florida
- Abstract / Description
-
The revolution in chip manufacturing processes spanning five decades has proliferated high performance and energy-efficient nano-electronic devices across all aspects of daily life. In recent years, CMOS technology scaling has realized billions of transistors within large-scale VLSI chips to elevate performance. However, these advancements have also continually augmented the impact of Single-Event Transient (SET) and Single-Event Upset (SEU) occurrences which precipitate a range of Soft-Error...
Show moreThe revolution in chip manufacturing processes spanning five decades has proliferated high performance and energy-efficient nano-electronic devices across all aspects of daily life. In recent years, CMOS technology scaling has realized billions of transistors within large-scale VLSI chips to elevate performance. However, these advancements have also continually augmented the impact of Single-Event Transient (SET) and Single-Event Upset (SEU) occurrences which precipitate a range of Soft-Error (SE) dependability issues. Consequently, soft-error mitigation techniques have become essential to improve systems' reliability. Herein, first, we proposed optimized soft-error resilience designs to improve robustness of sub-micron computing systems. The proposed approaches were developed to deliver energy-efficiency and tolerate double/multiple errors simultaneously while incurring acceptable speed performance degradation compared to the prior work. Secondly, the impact of Process Variation (PV) at the Near-Threshold Voltage (NTV) region on redundancy-based SE-mitigation approaches for High-Performance Computing (HPC) systems was investigated to highlight the approach that can realize favorable attributes, such as reduced critical datapath delay variation and low speed degradation. Finally, recently, spin-based devices have been widely used to design Non-Volatile (NV) elements such as NV latches and flip-flops, which can be leveraged in normally-off computing architectures for Internet-of-Things (IoT) and energy-harvesting-powered applications. Thus, in the last portion of this dissertation, we design and evaluate for soft-error resilience NV-latching circuits that can achieve intriguing features, such as low energy consumption, high computing performance, and superior soft errors tolerance, i.e., concurrently able to tolerate Multiple Node Upset (MNU), to potentially become a mainstream solution for the aerospace and avionic nanoelectronics. Together, these objectives cooperate to increase energy-efficiency and soft errors mitigation resiliency of larger-scale emerging NV latching circuits within iso-energy constraints. In summary, addressing these reliability concerns is paramount to successful deployment of future reliable and energy-efficient CMOS logic and spintronic memory architectures with deeply-scaled devices operating at low-voltages.
Show less - Date Issued
- 2019
- Identifier
- CFE0007884, ucf:52765
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007884
- Title
- Modeling and Transient Simulation of a Fully Integrated Multi-Pressure Heat Recovery Steam Generator Using Siemens T3000.
- Creator
-
McConnell, Jonathan, Das, Tuhin, Chow, Louis, Tian, Tian, University of Central Florida
- Abstract / Description
-
The focus of this research is on the transient thermodynamic properties and dynamic behavior of a Heat Recovery Steam Generator (HRSG). An HRSG is a crossflow heat exchanger designed for the extraction of energy from the hot exhaust gas of a traditional power plant through boiling induced phase change. Superheated steam is sent through a turbine to generate additional power, raising the overall efficiency of a power plant. The addition of renewable energies and the evolution of smart grids...
Show moreThe focus of this research is on the transient thermodynamic properties and dynamic behavior of a Heat Recovery Steam Generator (HRSG). An HRSG is a crossflow heat exchanger designed for the extraction of energy from the hot exhaust gas of a traditional power plant through boiling induced phase change. Superheated steam is sent through a turbine to generate additional power, raising the overall efficiency of a power plant. The addition of renewable energies and the evolution of smart grids have brought forth a necessity to gain a comprehensive understanding of transient behavior within an HRSG in order to efficiently manage the power output of traditional plants. Model-based techniques that can simulate a wide range of operating conditions can be valuable and insightful. For this reason, a multi-physics model of an HRSG has been developed in Siemens T3000 plant monitoring software. The layout and conditions of a reference HRSG have been provided by Siemens Energy Inc. along with validation data for behavioral comparison. The HRSG selected is a three pressure stage HRSG. Simultaneous simulation of these three pressure systems and their interactions has been achieved. A potential for real time execution was demonstrated. An HRSG is built of three major subsystems, namely economizers, boilers, and superheaters. A lumped control volume approach has been implemented to efficiently model the energy and mass balances of medium within each subsystem. In this effort, considering the goal of real time simulation, special attention was paid to balance computational burden with numerical accuracy.A major focus of this research has been accurately modeling the complexities of phase change within a boiler subsystem. A switching mechanism has been developed to numerically model the dynamic heating and evaporation of boiler liquid. To increase robustness of the model to numerical fluctuations and perturbations, bidirectional flow comprising of boiling and condensation was modeled with the switching mechanism. This numerically robust model shows good agreement with the validation data provided by Siemens.
Show less - Date Issued
- 2019
- Identifier
- CFE0007683, ucf:52459
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007683
