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Title: DFT STUDY OF GEOMETRY AND ENERGETICS OF TRANSITION METAL SYSTEMS.
Creator: Goel, Satyender, MASUNOV, ARTEM, University of Central Florida
Abstract / Description: This dissertation focuses on computational study of the geometry and energetics small molecules and nanoclusters involving transition metals (TM). These clusters may be used for various industrial applications including catalysis and photonics. Specifically, in this work we have studied hydrides and carbides of 3d-transition metal systems (Sc through Cu), small nickel and gold clusters. Qualitatively correct description of the bond dissociation is ensured by allowing the spatial and spin...
Show moreThis dissertation focuses on computational study of the geometry and energetics small molecules and nanoclusters involving transition metals (TM). These clusters may be used for various industrial applications including catalysis and photonics. Specifically, in this work we have studied hydrides and carbides of 3d-transition metal systems (Sc through Cu), small nickel and gold clusters. Qualitatively correct description of the bond dissociation is ensured by allowing the spatial and spin symmetry to break. We have tested applicability of new exchange-correlation functional and alternative theoretical descriptions (spin-contamination correction in broken symmetry DFT and ensemble Kohn-Sham (EKS)) as well. We studies TM hydrides and carbides systems to understand the importance of underlying phenomenon of bond breaking in catalytic processes. We have tested several exchange-correlation functionals including explicit dependence on kinetic energy density for the description of hydrides (both neutral and cationic) and carbides formed by 3d-transition metals. We find M05-2x and BMK dissociation energies are in better agreement with experiment (where available) than those obtained with high level wavefunction theory methods, published previously. This agreement with experiment deteriorates quickly for other functionals when the fraction of the Hartree-Fock exchange in DFT functional is decreased. Higher fraction of HF exchange is also essential in EKS formalism, but it does not help when spin-adapted unrestricted approach is employed. We analyze the electron spin densities using Natural Bond Orbital population analysis and find that simple description of 3d electrons as non-bonding in character is rarely correct. Unrestricted formalism results in appreciable spin-contamination for some of the systems at equilibrium, which motivated us to investigate it further in details. In order to correct the spin contamination effect on the energies, we propose a new scheme to correct for spin contamination arising in broken-symmetry DFT approach. Unlike conventional schemes, our spin correction is introduced for each spin-polarized electron pair individually and therefore is expected to yield more accurate energy values. We derive an expression to extract the energy of the pure singlet state from the energy of the broken-symmetry DFT description of the low spin state and the energies of the high spin states (pentuplet and two spin-contaminated triplets in the case of two spin-polarized electron pairs). We validate our spin-contamination correction approach by a simple example of H2 and applied to more complex MnH system. Ensemble KS formalism is also applied to investigate the dissociation of C2 molecule. We find that high fraction of HF exchange is essential to reproduce the results of EKS treatment with exact exchange-correlation functional. We analyze the geometry and energetics of small nickel clusters (Ni2-Ni5) for several lowest energy isomers. We also study all possible spin states of small nickel cluster isomers and report observed trends in energetics. Finally we determine the geometry and energetics of ten lowest energy isomers of four small gold clusters (Au2, Au4, Au6, and Au8). We have also investigated the influence of cluster geometry, ligation, solvation and relativistic effects on electronic structure of these gold clusters. The effect of one-by-one ligand attachment in vacuum and solvent environment is also studied. Performance of five DFT functionals are tested as well; Local Spin Density Approximation (SVWN5), Generalized Gradient Approximation (PBE), kinetic energy density-dependent functional (TPSS), hybrid DFT (B3LYP), and CAM-B3LYP which accounts for long-range exchange effects believed to be important in the analysis of metal bonding in gold complexes and clusters. Our results exhibit the ligand induced stability enhancement of otherwise less stable isomers of Au4, Au6 and Au8. Ligands are found to play a crucial role in determining the 2D to 3D transition realized in small gold clusters. In order to select an appropriate theory level to use in this study, we investigate the effect of attachment of four different ligands (NH3, NMe3, PH3, PMe3) on cluster geometry and energetics of Au2 and Au4 in vacuum and in solution. Our results benchmark the applicability of DFT functional model and polarization functions in the basis set for calculations of ligated gold cluster systems. We employ five different basis sets with increasing amount of polarization and diffuse functions; LANL2DZ, LANL2DZ-P, def2-SVP, def2-TZVP, and def2-QZVP. We obtain NMe3 = NH3 < PH3 < PMe3 order of ligand binding energies and observe shallow potential energy surfaces in all molecules. Our results suggest appropriate quantum-chemical methodologies to model small noble metal clusters in realistic ligand environment to provide reliable theoretical analysis in order to complement experiments.
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Date Issued: 2010
Identifier: CFE0003293, ucf:48498
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003293

Title: Energy Efficient and Secure Wireless Sensor Networks Design.
Creator: Attiah, Afraa, Zou, Changchun, Chatterjee, Mainak, Wang, Jun, Yuksel, Murat, Wang, Chung-Ching, University of Central Florida
Abstract / Description: ABSTRACTWireless Sensor Networks (WSNs) are emerging technologies that have the ability to sense,process, communicate, and transmit information to a destination, and they are expected to have significantimpact on the efficiency of many applications in various fields. The resource constraintsuch as limited battery power, is the greatest challenge in WSNs design as it affects the lifetimeand performance of the network. An energy efficient, secure, and trustworthy system is vital whena WSN...
Show moreABSTRACTWireless Sensor Networks (WSNs) are emerging technologies that have the ability to sense,process, communicate, and transmit information to a destination, and they are expected to have significantimpact on the efficiency of many applications in various fields. The resource constraintsuch as limited battery power, is the greatest challenge in WSNs design as it affects the lifetimeand performance of the network. An energy efficient, secure, and trustworthy system is vital whena WSN involves highly sensitive information. Thus, it is critical to design mechanisms that are energyefficient and secure while at the same time maintaining the desired level of quality of service.Inspired by these challenges, this dissertation is dedicated to exploiting optimization and gametheoretic approaches/solutions to handle several important issues in WSN communication, includingenergy efficiency, latency, congestion, dynamic traffic load, and security. We present severalnovel mechanisms to improve the security and energy efficiency of WSNs. Two new schemes areproposed for the network layer stack to achieve the following: (a) to enhance energy efficiencythrough optimized sleep intervals, that also considers the underlying dynamic traffic load and (b)to develop the routing protocol in order to handle wasted energy, congestion, and clustering. Wealso propose efficient routing and energy-efficient clustering algorithms based on optimization andgame theory. Furthermore, we propose a dynamic game theoretic framework (i.e., hyper defense)to analyze the interactions between attacker and defender as a non-cooperative security game thatconsiders the resource limitation. All the proposed schemes are validated by extensive experimentalanalyses, obtained by running simulations depicting various situations in WSNs in orderto represent real-world scenarios as realistically as possible. The results show that the proposedschemes achieve high performance in different terms, such as network lifetime, compared with thestate-of-the-art schemes.
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Date Issued: 2018
Identifier: CFE0006971, ucf:51672
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006971

Title: Biological Nutrient Removal (BNR) Process Optimization and Recovery of Embedded Energy Using Biodiesel By-product.
Creator: Salamah, Sultan, Randall, Andrew, Duranceau, Steven, Chopra, Manoj, University of Central Florida
Abstract / Description: Enhanced biological phosphorus removal (EBPR) as well as biological nitrogen removal require a carbon source to be carried out. Volatile fatty acid (VFAs) (mainly acetic and propionic acids) are the major driving force for EBPR. Many domestic wastewaters have an insufficient amount of VFAs. However, carbon sources such as acetic and propionic acids can be produced using primary solids fermentation process. Due to the cost of VFA production, an external carbon source can be added to the...
Show moreEnhanced biological phosphorus removal (EBPR) as well as biological nitrogen removal require a carbon source to be carried out. Volatile fatty acid (VFAs) (mainly acetic and propionic acids) are the major driving force for EBPR. Many domestic wastewaters have an insufficient amount of VFAs. However, carbon sources such as acetic and propionic acids can be produced using primary solids fermentation process. Due to the cost of VFA production, an external carbon source can be added to the biological nutrient removal (BNR) system that can be fermented to provide the desired VFAs. Glycerol (biodiesel by-product) offers a solution to reduce carbon addition cost if can be fermented to acetic and propionic acid or can be used directly as an external carbon substrate for EBPR and denitrification. Using glycerol in wastewater treatment can also offset the biodiesel plant disposal cost and reduce the BNR chemical cost. The main objective of this study was to optimize the prefermentation process and optimize the BNR system using glycerol as an external carbon source. In this work, Optimization of the prefermentation process using glycerol, mixing, and hydrogen gas addition was evaluated. EBPR performance within an A2O-BNR system was evaluated using either a direct glycerol method to the anaerobic zone or by co-fermentation with primary solids. Also, optimization of the nitrogen removal (specifically denitrification) efficiency of a 5-stage BardenphoTM BNR system using either a direct glycerol method to the second anoxic zone or by co-fermentation with primary solids was evaluated. It was found in this study that glycerol was an efficient external carbon substrate for EBPR as well as biological nitrogen removal. The prefermentation experiment showed that glycerol co-fermentation with primary solids produced significantly higher (p(<)0.05) VFAs than primary solids fermentation alone, even more than the possible value from the added glycerol (427 mg-COD/L). The increased VFAs imply that the glycerol addition stimulated additional fermentation of primary solids. Lowering the prefermenter mixing energy (50 to 7 rpm) resulted in a significant increase in VFAs production (80%). Also, purging the headspace of the prefermenter with hydrogen gas did not lead to more VFAs, but significantly (p(<)0.05) increased the propionic acid to acetic acid ratio by 41%. In the A2O-BNR pilot plant experiment, it was found that glycerol is a suitable renewable external substrate to drive enhanced EBPR as well as denitrification. The results from both locations of glycerol addition (direct vs. fermented) were beneficial to the BNR system. Both systems had similar effluent quality and achieved total nitrogen (TN) and total phosphorus (TP) removals up to 86% and 92% respectively. The 5-stage BardenphoTM BNR experiment investigated the location of glycerol addition (direct vs. fermented) on the performance of denitrification in the second anoxic zone and the overall performance. The results from both systems were that glycerol was beneficial to the BNR system and had virtually similar effluent quality. Both systems achieve complete denitrification and excellent removal of TN and TP up to 95% and 89% respectively. Also, the pilot that received fermented glycerol had significantly higher VFAs loading and lower observed yield. The side-stream prefermenter effluent flowing to the second anoxic reactor did not cause high effluent ammonia (NH3) concentration. In summary, the location at which glycerol was added did not affect effluent quality for nitrogen and phosphorus. However, glycerol addition and mixing energy did impact prefermenter performance and effluent quality.
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Date Issued: 2017
Identifier: CFE0006788, ucf:51826
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006788

Title: A GASOLINE DEMAND MODEL FOR THE UNITED STATES LIGHT VEHICLE FLEET.
Creator: Rey, Diana, Al-Deek, Haitham, University of Central Florida
Abstract / Description: ABSTRACT The United States is the world's largest oil consumer demanding about twenty five percent of the total world oil production. Whenever there are difficulties to supply the increasing quantities of oil demanded by the market, the price of oil escalates leading to what is known as oil price spikes or oil price shocks. The last oil price shock which was the longest sustained oil price run up in history, began its course in year 2004, and ended in 2008. This last oil price shock...
Show moreABSTRACT The United States is the world's largest oil consumer demanding about twenty five percent of the total world oil production. Whenever there are difficulties to supply the increasing quantities of oil demanded by the market, the price of oil escalates leading to what is known as oil price spikes or oil price shocks. The last oil price shock which was the longest sustained oil price run up in history, began its course in year 2004, and ended in 2008. This last oil price shock initiated recognizable changes in transportation dynamics: transit operators realized that commuters switched to transit as a way to save gasoline costs, consumers began to search the market for more efficient vehicles leading car manufactures to close "gas guzzlers" plants, and the government enacted a new law entitled the Energy Independence Act of 2007, which called for the progressive improvement of the fuel efficiency indicator of the light vehicle fleet up to 35 miles per gallon in year 2020. The past trend of gasoline consumption will probably change; so in the context of the problem a gasoline consumption model was developed in this thesis to ascertain how some of the changes will impact future gasoline demand. Gasoline demand was expressed in oil equivalent million barrels per day, in a two steps Ordinary Least Square (OLS) explanatory variable model. In the first step, vehicle miles traveled expressed in trillion vehicle miles was regressed on the independent variables: vehicles expressed in million vehicles, and price of oil expressed in dollars per barrel. In the second step, the fuel consumption in million barrels per day was regressed on vehicle miles traveled, and on the fuel efficiency indicator expressed in miles per gallon. The explanatory model was run in EVIEWS that allows checking for normality, heteroskedasticty, and serial correlation. Serial correlation was addressed by inclusion of autoregressive or moving average error correction terms. Multicollinearity was solved by first differencing. The 36 year sample series set (1970-2006) was divided into a 30 years sub-period for calibration and a 6 year "hold-out" sub-period for validation. The Root Mean Square Error or RMSE criterion was adopted to select the "best model" among other possible choices, although other criteria were also recorded. Three scenarios for the size of the light vehicle fleet in a forecasting period up to 2020 were created. These scenarios were equivalent to growth rates of 2.1, 1.28, and about 1 per cent per year. The last or more optimistic vehicle growth scenario, from the gasoline consumption perspective, appeared consistent with the theory of vehicle saturation. One scenario for the average miles per gallon indicator was created for each one of the size of fleet indicators by distributing the fleet every year assuming a 7 percent replacement rate. Three scenarios for the price of oil were also created: the first one used the average price of oil in the sample since 1970, the second was obtained by extending the price trend by exponential smoothing, and the third one used a longtime forecast supplied by the Energy Information Administration. The three scenarios created for the price of oil covered a range between a low of about 42 dollars per barrel to highs in the low 100's. The 1970-2006 gasoline consumption trend was extended to year 2020 by ARIMA Box-Jenkins time series analysis, leading to a gasoline consumption value of about 10 millions barrels per day in year 2020. This trend line was taken as the reference or baseline of gasoline consumption. The savings that resulted by application of the explanatory variable OLS model were measured against such a baseline of gasoline consumption. Even on the most pessimistic scenario the savings obtained by the progressive improvement of the fuel efficiency indicator seem enough to offset the increase in consumption that otherwise would have occurred by extension of the trend, leaving consumption at the 2006 levels or about 9 million barrels per day. The most optimistic scenario led to savings up to about 2 million barrels per day below the 2006 level or about 3 millions barrels per day below the baseline in 2020. The "expected" or average consumption in 2020 is about 8 million barrels per day, 2 million barrels below the baseline or 1 million below the 2006 consumption level. More savings are possible if technologies such as plug-in hybrids that have been already implemented in other countries take over soon, are efficiently promoted, or are given incentives or subsidies such as tax credits. The savings in gasoline consumption may in the future contribute to stabilize the price of oil as worldwide demand is tamed by oil saving policy changes implemented in the United States.
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Date Issued: 2009
Identifier: CFE0002539, ucf:47659
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002539

Title: The Performance and Power Impact of Using Multiple DRAM Address Mapping Schemes in Multicore Processors.
Creator: Jadaa, Rami, Heinrich, Mark, DeMara, Ronald, Yuan, Jiann-Shiun, University of Central Florida
Abstract / Description: Lowest-level cache misses are satisfied by the main memory through a specific address mapping scheme that is hard-coded in the memory controller. A dynamic address mapping scheme technique is investigated to provide higher performance and lower power consumption, and a method to throttle memory to meet a specific power budget. Several experiments are conducted on single and multithreaded synthetic memory traces -to study extreme cases- and validate the usability of the proposed dynamic...
Show moreLowest-level cache misses are satisfied by the main memory through a specific address mapping scheme that is hard-coded in the memory controller. A dynamic address mapping scheme technique is investigated to provide higher performance and lower power consumption, and a method to throttle memory to meet a specific power budget. Several experiments are conducted on single and multithreaded synthetic memory traces -to study extreme cases- and validate the usability of the proposed dynamic mapping scheme over the fixed one. Results show that applications' performance varies according to the mapping scheme used, and a dynamic mapping scheme achieves up to 2x increase in peak bandwidth utilization and around 30% higher energy efficiency than a system using only a single fixed scheme Moreover, the technique can be used to limit memory accesses into a subset of the memory devices by controlling data allocation at a finer granularity, providing a method to throttle main memory by allowing un-accessed devices to be put into power-down mode, hence saving power to meet a certain power budget.
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Date Issued: 2011
Identifier: CFE0004121, ucf:49118
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004121

Title: DESIGN AND OPERATION OF STATIONARY DISTRIBUTED BATTERY MICRO-STORAGE SYSTEMS.
Creator: Al-Haj Hussein, Ala, Batarseh, Issa, University of Central Florida
Abstract / Description: Due to some technical and environmental constraints, expanding the current electric power generation and transmission system is being challenged by even increasing the deployment of distributed renewable generation and storage systems. Energy storage can be used to store energy from utility during low-demand (off-peak) hours and deliver this energy back to the utility during high-demand (on-peak) hours. Furthermore, energy storage can be used with renewable sources to overcome some of their...
Show moreDue to some technical and environmental constraints, expanding the current electric power generation and transmission system is being challenged by even increasing the deployment of distributed renewable generation and storage systems. Energy storage can be used to store energy from utility during low-demand (off-peak) hours and deliver this energy back to the utility during high-demand (on-peak) hours. Furthermore, energy storage can be used with renewable sources to overcome some of their limitations such as their strong dependence on the weather conditions, which cannot be perfectly predicted, and their unmatched or out-of-synchronization generation peaks with the demand peaks. Generally, energy storage enhances the performance of distributed renewable sources and increases the efficiency of the entire power system. Moreover, energy storage allows for leveling the load, shaving peak demands, and furthermore, transacting power with the utility grid. This research proposes an energy management system (EMS) to manage the operation of distributed grid-tied battery micro-storage systems for stationary applications when operated with and without renewable sources. The term "micro" refers to the capacity of the energy storage compared to the grid capacity. The proposed management system employs four dynamic models; economic model, battery model, and load and weather forecasting models. These models, which are the main contribution of this research, are used in order to optimally control the operation of the micro-storage system (MSS) to maximize the economic return for the end-user when operated in an electricity spot market system.
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Date Issued: 2011
Identifier: CFE0003964, ucf:48712
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003964

Title: Towards Energy-Efficient and Reliable Computing: From Highly-Scaled CMOS Devices to Resistive Memories.
Creator: Salehi Mobarakeh, Soheil, DeMara, Ronald, Fan, Deliang, Turgut, Damla, University of Central Florida
Abstract / Description: The continuous increase in transistor density based on Moore's Law has led us to highly scaled Complementary Metal-Oxide Semiconductor (CMOS) technologies. These transistor-based process technologies offer improved density as well as a reduction in nominal supply voltage. An analysis regarding different aspects of 45nm and 15nm technologies, such as power consumption and cell area to compare these two technologies is proposed on an IEEE 754 Single Precision Floating-Point Unit implementation....
Show moreThe continuous increase in transistor density based on Moore's Law has led us to highly scaled Complementary Metal-Oxide Semiconductor (CMOS) technologies. These transistor-based process technologies offer improved density as well as a reduction in nominal supply voltage. An analysis regarding different aspects of 45nm and 15nm technologies, such as power consumption and cell area to compare these two technologies is proposed on an IEEE 754 Single Precision Floating-Point Unit implementation. Based on the results, using the 15nm technology offers 4-times less energy and 3-fold smaller footprint. New challenges also arise, such as relative proportion of leakage power in standby mode that can be addressed by post-CMOS technologies. Spin-Transfer Torque Random Access Memory (STT-MRAM) has been explored as a post-CMOS technology for embedded and data storage applications seeking non-volatility, near-zero standby energy, and high density. Towards attaining these objectives for practical implementations, various techniques to mitigate the specific reliability challenges associated with STT-MRAM elements are surveyed, classified, and assessed herein. Cost and suitability metrics assessed include the area of nanomagmetic and CMOS components per bit, access time and complexity, Sense Margin (SM), and energy or power consumption costs versus resiliency benefits. In an attempt to further improve the Process Variation (PV) immunity of the Sense Amplifiers (SAs), a new SA has been introduced called Adaptive Sense Amplifier (ASA). ASA can benefit from low Bit Error Rate (BER) and low Energy Delay Product (EDP) by combining the properties of two of the commonly used SAs, Pre-Charge Sense Amplifier (PCSA) and Separated Pre-Charge Sense Amplifier (SPCSA). ASA can operate in either PCSA or SPCSA mode based on the requirements of the circuit such as energy efficiency or reliability. Then, ASA is utilized to propose a novel approach to actually leverage the PV in Non-Volatile Memory (NVM) arrays using Self-Organized Sub-bank (SOS) design. SOS engages the preferred SA alternative based on the intrinsic as-built behavior of the resistive sensing timing margin to reduce the latency and power consumption while maintaining acceptable access time.
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Date Issued: 2016
Identifier: CFE0006493, ucf:51400
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006493

Title: Design and modeling of a heat exchanger for porous combustor powered steam generators in automotive industry.
Creator: Dasgupta, Apratim, Orlovskaya, Nina, Gou, Jihua, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: A major challenge faced by automobile manufacturers is to achieve reduction of particulate emission to acceptable standards, as the emission standards become more and more stringent. One of the ecologically friendly options to reduce emissions is to develop external combustion in a steam engine as a replacement of the internal combustion engine. There are multiple factors, other than pollution that need to be considered for developing a substitute for Internal Combustion Engine, like specific...
Show moreA major challenge faced by automobile manufacturers is to achieve reduction of particulate emission to acceptable standards, as the emission standards become more and more stringent. One of the ecologically friendly options to reduce emissions is to develop external combustion in a steam engine as a replacement of the internal combustion engine. There are multiple factors, other than pollution that need to be considered for developing a substitute for Internal Combustion Engine, like specific power, throttle response, torque speed curve, fuel consumption and refueling infrastructure. External combustion in a steam engine seems to be a bright idea, for a cleaner and more environment friendly alternative to the IC engine that can satisfy the multiple technology requirements mentioned. One way of performing external heterogeneous combustion is to use porous ceramic media, which is a modern and innovative technique, used in many practical applications. The heterogeneous combustion inside ceramic porous media provides numerous advantages, as the ceramic, acts as a regenerator that distributes heat from the flue gases to the upstream reactants, resulting in the extended flammability limits of the reactants. The heat exchanger design is the major challenge in developing an external combustion engine because of the space, such systems consume in an automobile. The goal of the research is to develop a compact and efficient heat exchanger for the application. The proposed research uses natural gas as a fuel that is mixed with air for combustion and the generated flue gases are fed to a heat exchanger to generate superheated system for performing engine work to the vehicle. The performed research is focused on designing and modeling of the boiler heat exchanger section. The justification for selection of working fluid and power plant technology is presented as part of the research, where the proposed system consists of an Air and Flue Gas Path and a Water and Steam Path. Models are developed for coupled thermal and fluid analysis of a heat exchanger, consisting of three sections. The first section converts water to a saturated liquid. The second portion consists of a section where water is converted to saturated steam. The third section is the superheater, where saturated steam is converted to superheated steam. The Finite Element Model is appropriately meshed and boundary conditions set up to solve the mass, momentum and energy conservation equations. The k-epsilon model is implemented to take care of turbulence. Analytical calculations following the established codes and standards are also executed to develop the design.
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Date Issued: 2017
Identifier: CFE0006579, ucf:51308
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006579

Title: Three-phase contact line phenomena in droplets on solid and liquid surfaces: electrocapillary, pinning, wetting line velocity effect, and free liquid surface deformation.
Creator: Shabani, Roxana, Cho, Hyoung, Kumar, Ranganathan, Kapat, Jayanta, Chow, Louis, Zhai, Lei, University of Central Florida
Abstract / Description: In this dissertation, physical phenomena relevant to (i) an interface formed between two fluids and a solid phase (wettingline) and (ii) an interface between three fluids (triple contact line) were investigated. In the former case, the wetting line (WL)phenomena, which encompass the wetting line energy (WLE), the wetting line velocity (WLV), and the contact anglehysteresis, were studied using a micropump based on electrowetting on dielectric (EWOD). In the latter case, the air filmlubrication...
Show moreIn this dissertation, physical phenomena relevant to (i) an interface formed between two fluids and a solid phase (wettingline) and (ii) an interface between three fluids (triple contact line) were investigated. In the former case, the wetting line (WL)phenomena, which encompass the wetting line energy (WLE), the wetting line velocity (WLV), and the contact anglehysteresis, were studied using a micropump based on electrowetting on dielectric (EWOD). In the latter case, the air filmlubrication effect and the liquid free surface deformation were taken into account to explain the dual equilibrium states ofwater droplets on liquid free surfaces. A micropump based on droplet/meniscus pressure gradient generated by EWOD was designed and fabricated. By alteringthe contact angle between liquid and solid using an electric field a pressure gradient was induced and a small droplet waspumped into the channel. The flow rate in the channel was found to be constant in spite of the changes in the droplet'sradius. The WL phenomena were studied to unravel the physical concept behind the micropump constant flow rate. Theobservation and measurement reveal that the shrinking input droplet changes its shape in two modes in time sequence: (i)its contact angle decreases, while its wetting area remains constant, and (ii) its WL starts to move while its contact anglechanges. Contact angles were measured for the advancing and receding WLs at different velocities to capture a full pictureof contact angle behavior. The effects of the WLE on the static contact angle and the WLV on the dynamic contact angle inthe pump operation were investigated. Also the effect of EWOD voltage on the magnitude and uniformity of the micropumpflow rate was studied. Dynamic contact angles were used to accurately calculate the pressure gradient between the dropletand the meniscus, and estimate the flow rate. It was shown that neglecting either of these effects not only results in aconsiderable gap between the predicted and the measured flow rates but also in an unphysical instability in the flow rateanalysis. However, when the WLE and WLV effects were fully taken into account, an excellent agreement between thepredicted and the experimental flow rates was obtained.For the study of the TCL between three fluids, aqueous droplets were formed at oil-air interface and two stableconfigurations of (i) non-coalescent droplet and (ii) cap/bead droplet were observed. General solutions for energy and forceanalysis were obtained and were shown to be in good agreement with the experimental observations. Further the energybarrier obtained for transition from configuration (i) to (ii) was correlated to the droplet release height and the probability ofnon-coalescent droplet formation. Droplets formed on the solid surfaces and on the free surface of immiscible liquids have various applications indroplet-based microfluidic devices. This research provides an insight into their formation and manipulation.
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Date Issued: 2013
Identifier: CFE0005253, ucf:50598
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005253

Title: Nano-Particles in Multi-Scale Composites and Ballistic Applications.
Creator: Gibson, Jason, Gou, Jihua, Raghavan, Seetha, Bai, Yuanli, Zhai, Lei, University of Central Florida
Abstract / Description: Carbon nanotubes, graphene and nano sized core shell rubber particles have all been extensively researched for their capability to improve mechanical properties of thermoset resins. However, there has been a lack of research on their evaluation for energy absorption in high velocity impact scenarios, and the fundamental mechanics of their failure mechanisms during highly dynamic stress transfer through the matrix. This fundamental research is essential for laying the foundation for...
Show moreCarbon nanotubes, graphene and nano sized core shell rubber particles have all been extensively researched for their capability to improve mechanical properties of thermoset resins. However, there has been a lack of research on their evaluation for energy absorption in high velocity impact scenarios, and the fundamental mechanics of their failure mechanisms during highly dynamic stress transfer through the matrix. This fundamental research is essential for laying the foundation for improvement in ballistic performance in composite armor. In hard armor applications, energy absorption is largely accomplished through delamination between plies of the composite laminate. This energy absorption is accomplished through two mechanisms. The first being the elongation of the fiber reinforcement contained in the resin matrix, and the second is the propagation of the crack in between the discreet fabric plies. This research aims to fundamentally study the energy absorption characteristics of various nano-particles as reinforcements in thermoset resin for high velocity impact applications. Multiple morphologies will be evaluated through use of platelet, tubular and spherical shaped nano-particles. Evaluations of the effect on stress transfer through the matrix due to the combination of nano sized and micro scale particles of milled fiber is conducted. Three different nano-particles are utilized, specifically, multi-walled carbon nanotubes, graphene, and core shell rubber particles. The difference in surface area, aspect ratio and molecular structure between the tube, platelet and spherical nano-particles causes energy absorption through different failure mechanisms. This changes the impact performance of composite panels enhanced with the nano-particle fillers. Composite panels made through the use of dispersing the various nano-particles in a non-contact planetary mixer, are evaluated through various dynamic and static testing, including unnotched cantilever beam impact, mixed mode fracture toughness, split-Hopkinson bar, and ballistic V50 testing.The unnotched cantilever beam testing showed that the addition of milled fiber degraded the impact resistance of the samples. Addition of graphene nano platelets unilaterally degraded impact resistance through the unnotched cantilever beam testing. 1.5% loading of MWCNT showed the greatest increase in impact resistance, with a 43% increase over baseline.Determining the critical load for mixed mode interlaminar shear testing can be difficult for composite panels that bend without breaking. An iterative technique of optimizing the coefficient of determination, R2, in linear regression is developed for objectively determining the point of non-linearity for critical load. This allows for a mathematical method of determination; thereby eliminating any subjective decision of choosing where the data becomes non-linear. The core shell rubber nano particles showed the greatest strain energy release rate with an exponential improvement over the baseline results.Synergistic effects between nano and micro sized particles in the resin matrix during transfer of the stress wave were created and evaluated. Loadings of 1% milled carbon fiber enhanced the V50 ballistic performance of both carbon nanotube and core shell rubber particles in the resin matrix. However, the addition of milled carbon fiber degrades the impact resistance of all nano-particle enhanced resin matrices. Therefore, benefits gained from the addition of micro-sized particles in combination with nano-sized particles, are only seen in high energy impact scenarios with micro second durations.Loadings of 1% core shell rubber particles and 1% milled carbon fiber have an improvement of 8% in V50 ballistic performance over the baseline epoxy sample for 44 mag single wad cutter gas check projectiles. Loadings of 1% multi-walled carbon nanotubes with 1% milled carbon fiber have an improvement of 7.3% in V50 ballistic performance over the baseline epoxy sample.The failure mechanism of the various nano-particle enhanced resin matrices during the ballistic event is discussed through the use of scanning electron microscope images and Raman spectroscopy of the panels after failure. The Raman spectroscopy data shows a Raman shift for the fibers that had an enhancement in the V50 performance through the use of nano-particles. The Raman band for Kevlar(&)#174; centered at 1,649 cm-1 stemming from the stretching of the C==O bond of the fiber shows to be more sensitive to the residual axial strain, while the Raman band centered at 1,611 cm-1 stemming from the C-C phenyl ring is minimally affected for the CSR enhanced panels due to the failure mechanism of the CSR particles during crack propagation.
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Date Issued: 2013
Identifier: CFE0004849, ucf:49714
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004849

Title: Design and Implementation of PV-Firming and Optimization Algorithms For Three-Port Microinverters.
Creator: Alharbi, Mahmood, Batarseh, Issa, Haralambous, Michael, Mikhael, Wasfy, Yuan, Jiann-Shiun, Kutkut, Nasser, University of Central Florida
Abstract / Description: With the demand increase for electricity, the ever-increasing awareness of environmental issues, coupled with rolling blackouts, the role of renewable energy generation is increasing along with the thirst for electricity and awareness of environmental issues. This dissertation proposes the design and implementation of PV-firming and optimization algorithms for three-port microinverters.Novel strategies are proposed in Chapters 3 and 4 for harvesting stable solar power in spite of intermittent...
Show moreWith the demand increase for electricity, the ever-increasing awareness of environmental issues, coupled with rolling blackouts, the role of renewable energy generation is increasing along with the thirst for electricity and awareness of environmental issues. This dissertation proposes the design and implementation of PV-firming and optimization algorithms for three-port microinverters.Novel strategies are proposed in Chapters 3 and 4 for harvesting stable solar power in spite of intermittent solar irradiance. PV firming is implemented using a panel-level three-port grid-tied PV microinverter system instead of the traditional high-power energy storage and management system at the utility scale. The microinverter system consists of a flyback converter and an H-bridge inverter/rectifier, with a battery connected to the DC-link. The key to these strategies lies in using static and dynamic algorithms to generate a smooth PV reference power. The outcomes are applied to various control methods to charge/discharge the battery so that a stable power generation profile is obtained. In addition, frequency-based optimization for the inverter stage is presented.One of the design parameters of grid-tied single-phase H-bridge sinusoidal pulse-width modulation (SPWM) microinverters is switching frequency. The selection of the switching frequency is a tradeoff between improving the power quality by reducing the total harmonic distortion (THD), and improving the efficiency by reducing the switching loss. In Chapter 5, two algorithms are proposed for optimizing both the power quality and the efficiency of the microinverter. They do this by using a frequency tracking technique that requires no hardware modification. The first algorithm tracks the optimal switching frequency for maximum efficiency at a given THD value. The second maximizes the power quality of the H-bridge micro-inverter by tracking the switching frequency that corresponds to the minimum THD.Real-time PV intermittency and usable capacity data were evaluated and then further analyzed in MATLAB/SIMULINK to validate the PV firming control. The proposed PV firming and optimization algorithms were experimentally verified, and the results evaluated. Finally, Chapter 6 provides a summary of key conclusions and future work to optimize the presented topology and algorithms.
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Date Issued: 2018
Identifier: CFE0007305, ucf:52166
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007305

Title: Shock Tube Investigations of Novel Combustion Environments Towards a Carbon-Neutral Future.
Creator: Barak, Samuel, Vasu Sumathi, Subith, Kapat, Jayanta, Ahmed, Kareem, University of Central Florida
Abstract / Description: Supercritical carbon dioxide (sCO2) cycles are being investigated for the future of power generation. These cycles will contribute to a carbon-neutral future to combat the effects of climate change. These direct-fired closed cycles will produce power without adding significant pollutants to the atmosphere. For these cycles to be efficient, they will need to operate at significantly higher pressures (e.g., 300 atm for Allam Cycle) than existing systems (typically less than 40 atm). There is...
Show moreSupercritical carbon dioxide (sCO2) cycles are being investigated for the future of power generation. These cycles will contribute to a carbon-neutral future to combat the effects of climate change. These direct-fired closed cycles will produce power without adding significant pollutants to the atmosphere. For these cycles to be efficient, they will need to operate at significantly higher pressures (e.g., 300 atm for Allam Cycle) than existing systems (typically less than 40 atm). There is limited knowledge on combustion at these pressures or at the high dilution of carbon dioxide. Nominal fuel choices for gas turbines include natural gas and syngas (mixture of CO and H2). Shock tubes study these problems in order to understand the fundamentals and solve various challenges. Shock tube experiments have been studied by the author in the sCO2 regime for various fuels including natural gas, methane and syngas. Using the shock tube to take measurements, pressure and light emissions time-histories measurements were taken at a 2-cm axial location away from the end wall. Experiments for syngas at lower pressure utilized high-speed imaging through the end wall to investigate the effects of bifurcation. It was found that carbon dioxide created unique interactions with the shock tube compared to tradition bath gasses such as argon. The experimental results were compared to predictions from leading chemical kinetic mechanisms. In general, mechanisms can predict the experimental data for methane and other hydrocarbon fuels; however, the models overpredict for syngas mixtures. Reaction pathway analysis was evaluated to determine where the models need improvements. A new shock tube has been designed and built to operate up to 1000 atm pressures for future high-pressure experiments. Details of this new facility are included in this work. The experiments in this work are necessary for mechanism development to design an efficient combustor operate these cycles.
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Date Issued: 2019
Identifier: CFE0007781, ucf:52359
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007781

Title: Resource Management in Large-scale Systems.
Creator: Paya, Ashkan, Marinescu, Dan, Wocjan, Pawel, Bassiouni, Mostafa, Mucciolo, Eduardo, University of Central Florida
Abstract / Description: The focus of this thesis is resource management in large-scale systems. Our primary concerns are energy management and practical principles for self-organization and self-management. The main contributions of our work are:1. Models. We proposed several models for different aspects of resource management, e.g., energy-aware load balancing and application scaling for the cloud ecosystem, hierarchical architecture model for self-organizing and self-manageable systems and a new cloud delivery...
Show moreThe focus of this thesis is resource management in large-scale systems. Our primary concerns are energy management and practical principles for self-organization and self-management. The main contributions of our work are:1. Models. We proposed several models for different aspects of resource management, e.g., energy-aware load balancing and application scaling for the cloud ecosystem, hierarchical architecture model for self-organizing and self-manageable systems and a new cloud delivery model based on auction-driven self-organization approach.2. Algorithms. We also proposed several different algorithms for the models described above. Algorithms such as coalition formation, combinatorial auctions and clustering algorithm for scale-free organizations of scale-free networks.3. Evaluation. Eventually we conducted different evaluations for the proposed models and algorithms in order to verify them. All the simulations reported in this thesis had been carried out on different instances and services of Amazon Web Services (AWS).All of these modules will be discussed in detail in the following chapters respectively.
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Date Issued: 2015
Identifier: CFE0005862, ucf:50913
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005862

Title: Engineering and Application of Ultrafast Laser Pulses and Filamentation in Air.
Creator: Barbieri, Nicholas, Richardson, Martin, University of Central Florida
Abstract / Description: Continuing advances in laser and photonic technology has seen the development of lasers with increasing power and increasingly short pulsewidths, which have become available over an increasing range of wavelengths. As the availability of laser sources grow, so do their applications. To make better use of this improving technology, understanding and controlling laser propagation in free space is critical, as is understanding the interaction between laser light and matter.The need to better...
Show moreContinuing advances in laser and photonic technology has seen the development of lasers with increasing power and increasingly short pulsewidths, which have become available over an increasing range of wavelengths. As the availability of laser sources grow, so do their applications. To make better use of this improving technology, understanding and controlling laser propagation in free space is critical, as is understanding the interaction between laser light and matter.The need to better control the light obtained from increasingly advanced laser sources leads to the emergence of beam engineering, the systematic understanding and control of light through refractive media and free space. Beam engineering enables control over the beam shape, energy and spectral composition during propagation, which can be achieved through a variety of means. In this dissertation, several methods of beam engineering are investigated. These methods enable improved control over the shape and propagation of laser light. Laser-matter interaction is also investigated, as it provides both a means to control the propagation of pulsed laser light through the atmosphere, and provides a means to generation remote sources of radiation.
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Date Issued: 2013
Identifier: CFE0004650, ucf:49881
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004650

Title: SPRAY COOLING FOR LAND, SEA, AIR AND SPACE BASED APPLICATIONS,A FLUID MANAGEMENT SYSTEM FOR MULTIPLE NOZZLE SPRAY COOLING AND A GUIDE TO HIGH HEAT FLUX HEATER DESIGN.
Creator: Glassman, Brian, Chow, Louis, University of Central Florida
Abstract / Description: This thesis is divided into four distinct chapters all linked by the topic of spray cooling. Chapter one gives a detailed categorization of future and current spray cooling applications, and reviews the major advantages and disadvantages that spray cooling has over other high heat flux cooling techniques. Chapter two outlines the developmental goals of spray cooling, which are to increase the output of a current system and to enable new technologies to be technically feasible. Furthermore,...
Show moreThis thesis is divided into four distinct chapters all linked by the topic of spray cooling. Chapter one gives a detailed categorization of future and current spray cooling applications, and reviews the major advantages and disadvantages that spray cooling has over other high heat flux cooling techniques. Chapter two outlines the developmental goals of spray cooling, which are to increase the output of a current system and to enable new technologies to be technically feasible. Furthermore, this chapter outlines in detail the impact that land, air, sea, and space environments have on the cooling system and what technologies could be enabled in each environment with the aid of spray cooling. In particular, the heat exchanger, condenser and radiator are analyzed in their corresponding environments. Chapter three presents an experimental investigation of a fluid management system for a large area multiple nozzle spray cooler. A fluid management or suction system was used to control the liquid film layer thickness needed for effective heat transfer. An array of sixteen pressure atomized spray nozzles along with an imbedded fluid suction system was constructed. Two surfaces were spray tested one being a clear grooved Plexiglas plate used for visualization and the other being a bottom heated grooved 4.5 x 4.5 cm2 copper plate used to determine the heat flux. The suction system utilized an array of thin copper tubes to extract excess liquid from the cooled surface. Pure water was ejected from two spray nozzle configurations at flow rates of 0.7 L/min to 1 L/min per nozzle. It was found that the fluid management system provided fluid removal efficiencies of 98% with a 4-nozzle array, and 90% with the full 16-nozzle array for the downward spraying orientation. The corresponding heat fluxes for the 16 nozzle configuration were found with and without the aid of the fluid management system. It was found that the fluid management system increased heat fluxes on the average of 30 W/cm2 at similar values of superheat. Unfortunately, the effectiveness of this array at removing heat at full levels of suction is approximately 50% & 40% of a single nozzle at respective 10„aC & 15„aC values of superheat. The heat transfer data more closely resembled convective pooling boiling. Thus, it was concluded that the poor heat transfer was due to flooding occurring which made the heat transfer mechanism mainly forced convective boiling and not spray cooling. Finally, Chapter four gives a detailed guide for the design and construction of a high heat flux heater for experimental uses where accurate measurements of surface temperatures and heat fluxes are extremely important. The heater designs presented allow for different testing applications; however, an emphasis is placed on heaters designed for use with spray cooling.
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Date Issued: 2005
Identifier: CFE0000473, ucf:46351
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000473

Title: A framework for interoperability on the United States electric grid infrastructure.
Creator: Laval, Stuart, Rabelo, Luis, Zheng, Qipeng, Xanthopoulos, Petros, Ajayi, Richard, University of Central Florida
Abstract / Description: Historically, the United States (US) electric grid has been a stable one-way power delivery infrastructure that supplies centrally-generated electricity to its predictably consuming demand. However, the US electric grid is now undergoing a huge transformation from a simple and static system to a complex and dynamic network, which is starting to interconnect intermittent distributed energy resources (DERs), portable electric vehicles (EVs), and load-altering home automation devices, that...
Show moreHistorically, the United States (US) electric grid has been a stable one-way power delivery infrastructure that supplies centrally-generated electricity to its predictably consuming demand. However, the US electric grid is now undergoing a huge transformation from a simple and static system to a complex and dynamic network, which is starting to interconnect intermittent distributed energy resources (DERs), portable electric vehicles (EVs), and load-altering home automation devices, that create bidirectional power flow or stochastic load behavior. In order for this grid of the future to effectively embrace the high penetration of these disruptive and fast-responding digital technologies without compromising its safety, reliability, and affordability, plug-and-play interoperability within the field area network must be enabled between operational technology (OT), information technology (IT), and telecommunication assets in order to seamlessly and securely integrate into the electric utility's operations and planning systems in a modular, flexible, and scalable fashion. This research proposes a potential approach to simplifying the translation and contextualization of operational data on the electric grid without being routed to the utility datacenter for a control decision. This methodology integrates modern software technology from other industries, along with utility industry-standard semantic models, to overcome information siloes and enable interoperability. By leveraging industrial engineering tools, a framework is also developed to help devise a reference architecture and use-case application process that is applied and validated at a US electric utility.
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Date Issued: 2015
Identifier: CFE0005647, ucf:50193
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005647

Title: Transient and Distributed Algorithms to Improve Islanding Detection Capability of Inverter Based Distributed Generation.
Creator: Alhosani, Mohamed, Qu, Zhihua, Mikhael, Wasfy, Haralambous, Michael, Behal, Aman, Xu, Chengying, University of Central Florida
Abstract / Description: Recently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten...
Show moreRecently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten years in anticipation of the tremendous increase in the penetration of Distributed Generation (DG) in distribution system. This work proposes new IDMs that rely on transient and distributed behaviors to improve integrity and performance of DGs while maintaining multi-DG islanding detection capability.In this thesis, the following questions have been addressed: How to utilize the transient behavior arising from an islanding condition to improve detectability and robust performance of IDMs in a distributive manner? How to reduce the negative stability impact of the well-known Sandia Frequency Shift (SFS) IDM while maintaining its islanding detection capability? How to incorporate the perturbations provided by each of DGs in such a way that the negative interference of different IDMs is minimized without the need of any type of communication among the different DGs?It is shown that the proposed techniques are local, scalable and robust against different loading conditions and topology changes. Also, the proposed techniques can successfully distinguish an islanding condition from other disturbances that may occur in power system networks. This work improves the efficiency, reliability and safety of integrated DGs, which presents a necessary advance toward making electric power grids a smart grid.
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Date Issued: 2013
Identifier: CFE0005295, ucf:50567
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005295

Title: Adaptive Architectural Strategies for Resilient Energy-Aware Computing.
Creator: Ashraf, Rizwan, DeMara, Ronald, Lin, Mingjie, Wang, Jun, Jha, Sumit, Johnson, Mark, University of Central Florida
Abstract / Description: Reconfigurable logic or Field-Programmable Gate Array (FPGA) devices have the ability to dynamically adapt the computational circuit based on user-specified or operating-condition requirements. Such hardware platforms are utilized in this dissertation to develop adaptive techniques for achieving reliable and sustainable operation while autonomously meeting these requirements. In particular, the properties of resource uniformity and in-field reconfiguration via on-chip processors are exploited...
Show moreReconfigurable logic or Field-Programmable Gate Array (FPGA) devices have the ability to dynamically adapt the computational circuit based on user-specified or operating-condition requirements. Such hardware platforms are utilized in this dissertation to develop adaptive techniques for achieving reliable and sustainable operation while autonomously meeting these requirements. In particular, the properties of resource uniformity and in-field reconfiguration via on-chip processors are exploited to implement Evolvable Hardware (EHW). EHW utilize genetic algorithms to realize logic circuits at runtime, as directed by the objective function. However, the size of problems solved using EHW as compared with traditional approaches has been limited to relatively compact circuits. This is due to the increase in complexity of the genetic algorithm with increase in circuit size. To address this research challenge of scalability, the Netlist-Driven Evolutionary Refurbishment (NDER) technique was designed and implemented herein to enable on-the-fly permanent fault mitigation in FPGA circuits. NDER has been shown to achieve refurbishment of relatively large sized benchmark circuits as compared to related works. Additionally, Design Diversity (DD) techniques which are used to aid such evolutionary refurbishment techniques are also proposed and the efficacy of various DD techniques is quantified and evaluated.Similarly, there exists a growing need for adaptable logic datapaths in custom-designed nanometer-scale ICs, for ensuring operational reliability in the presence of Process, Voltage, and Temperature (PVT) and, transistor-aging variations owing to decreased feature sizes for electronic devices. Without such adaptability, excessive design guardbands are required to maintain the desired integration and performance levels. To address these challenges, the circuit-level technique of Self-Recovery Enabled Logic (SREL) was designed herein. At design-time, vulnerable portions of the circuit identified using conventional Electronic Design Automation tools are replicated to provide post-fabrication adaptability via intelligent techniques. In-situ timing sensors are utilized in a feedback loop to activate suitable datapaths based on current conditions that optimize performance and energy consumption. Primarily, SREL is able to mitigate the timing degradations caused due to transistor aging effects in sub-micron devices by reducing the stress induced on active elements by utilizing power-gating. As a result, fewer guardbands need to be included to achieve comparable performance levels which leads to considerable energy savings over the operational lifetime.The need for energy-efficient operation in current computing systems has given rise to Near-Threshold Computing as opposed to the conventional approach of operating devices at nominal voltage. In particular, the goal of exascale computing initiative in High Performance Computing (HPC) is to achieve 1 EFLOPS under the power budget of 20MW. However, it comes at the cost of increased reliability concerns, such as the increase in performance variations and soft errors. This has given rise to increased resiliency requirements for HPC applications in terms of ensuring functionality within given error thresholds while operating at lower voltages. My dissertation research devised techniques and tools to quantify the effects of radiation-induced transient faults in distributed applications on large-scale systems. A combination of compiler-level code transformation and instrumentation are employed for runtime monitoring to assess the speed and depth of application state corruption as a result of fault injection. Finally, fault propagation models are derived for each HPC application that can be used to estimate the number of corrupted memory locations at runtime. Additionally, the tradeoffs between performance and vulnerability and the causal relations between compiler optimization and application vulnerability are investigated.
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Date Issued: 2015
Identifier: CFE0006206, ucf:52889
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006206

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