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Title: THE VAPORIZATION PHENOMENA OF FUEL DROPLETS EXPOSED TO ASYMMETRIC RADIANT HEATING USING PLANAR LASER-INDUCED FLUORESCENCE
Creator: Ammigan, Kavin
Date: 2012-04-17, 2012-05
Description: Droplet vaporization under asymmetric conditions is prevalent in many combustion related devices where fuel droplets may either experience...
Show moreDroplet vaporization under asymmetric conditions is prevalent in many combustion related devices where fuel droplets may either experience asymmetric thermal radiant heating or travel in velocity and temperature gradients. Asymmetric radiant heating is particularly common in spray flames, counter-flow diffusion flames, regions close to the walls of conventional combustion chambers and more importantly in liquid-fueled microcombustors. In this study, experiments are carried out to observe how droplets vaporize when exposed to asymmetric radiant heating. The experimental set-up consists of applying radiant heating, through a radiant panel heater, to one face of a monodisperse droplet stream while using the planar-laser induced fluorescence (PLIF) diagnostic tool to reveal the spatial vapor distribution around vaporizing droplets. Since most fuels are made up of multiple components, bicomponent droplets are also investigated. Pure acetone droplets as well as mixtures of acetone/alkanes (octane and hexane) and acetone/alcohols (ethanol and 2-propanol) droplets are investigated. Results in the form of PLIF images, reveal asymmetric vapor distributions around the droplets with the apparent induction of Stefan flow from the irradiated droplet surface. Such phenomena have not previously been reported in the literature and have relevance to the overall fuel vaporization process as well as subsequent ignition and pollutant formation processes. To further investigate the experimental results, a convective and radiative heat transfer model is employed to simulate the droplets under corresponding experimental conditions. Results from the model show convective cooling and a strong thermal radiation absorption near the droplets’ surface. The induced asymmetric Stefan flow observed experimentally is therefore a consequence of the high thermal radiation absorption at the droplets’ surface. This study gives both experimental and theoretical results of the vaporization phenomena of asymmetrically irradiated fuel droplets with varying compositions, diameters and irradiation temperatures.
Ph.D. in Mechanical and Aerospace Engineering, May 2012
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Title: ANALYSIS AND CONTROL OF COMPRESSION-IGNITION AND SPARK-IGNITED ENGINES OPERATING WITH DUAL-FUEL COMBUSTION STRATEGY
Creator: Kassa, Mateos
Date: 2017, 2017-07
Description: In recent years, the implementation of a dual-fuel combustion strategy has been explored as a means to improve the thermal efficiencies of...
Show moreIn recent years, the implementation of a dual-fuel combustion strategy has been explored as a means to improve the thermal efficiencies of internal combustion engines while simultaneously reducing their emissions. The dual-fuel combustion strategy was introduced in compression ignition engines to control the combustion phasing by varying the proportion of two simultaneously injected fuels, and altering the combustion timing. The dual-fuel injection strategy also allowed to extend the load limitation of advanced combustion engines, since the two injected fuel ignite in succession reducing the high peak pressures that generally act as a limiting factor. In spark-ignited (SI) engine, the implementation of a dual-fuel combustion strategy serves as an alternative approach to avoid knock (the inadvertent auto-ignition of the fuel mixture). Although conventional engines rely on delaying spark timing to avoid knocking cycles (which significantly reduces the thermal efficiency), the dual-fuel SI engine rely on the simultaneous injection of a low knock resistance and high knock resistance fuel to dynamically adjust the fuel resistance to knock as required. The dual-fuel SI engine thereby successfully suppresses knock without compromising the engine efficiency. Despite the benefits of the dual-fuel combustion strategy, several challenges arise in its implementation, especially when it is implemented along with other advanced combustion strategy leveraging variable valve timing, exhaust gas recirculation, turbocharging, and so forth. This study explores some of these challenges and addresses them from a control standpoint. Cylinder-to-cylinder variations is identified as one of the main challenges. An in-cylinder oxygen estimation strategy and modification to the conventional fueling strategy are proposed as approaches to reduce the combustion variations. In SI engines, the valve dynamics in transient operations are shown to negatively impact the dual-fuel control strategy. The effect of the valve timing on knock propensity and the resulting effect on the fueling strategy is investigated. Finally, the dual-fuel SI engine relies on measurements of the combustion intensity to adjust the fuel split between the low RON and high RON fuel. The implementation of a conventional knock control is shown to be counterintuitive for dual-fuel SI engines due to the highly reactive nature of the controller and the deterministic approach that assumes cycle-to-cycle correlation of the combustion intensity. Statistical investigation of the combustion intensity metric is conducted to identify key properties that can be leveraged for more effective control strategy.
Ph.D. in Mechanical, Material and Aerospace Engineering
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Title: SLIP-LINK MODELING OF ENTANGLED POLYMERS: RHEOLOGICAL APPLICATIONS AND EXTRACTING FRICTION FROM ATOMISTIC SIMULATION
Creator: Katzarova, Maria
Date: 2016, 2016-05
Description: The Discrete Slip-link Model (DSM) is a robust mesoscopic theory that has great success predicting the rheology of flexible entangled polymer...
Show moreThe Discrete Slip-link Model (DSM) is a robust mesoscopic theory that has great success predicting the rheology of flexible entangled polymer liquids and gels. In the most coarse-grained version of the DSM, we exploit the university observed in the shape of the relaxation modulus of linear monodisperse melts. For this type of polymer we present analytic expressions for the relaxation modulus. The high-frequency dynamics which are typically coarse-grained out from the DSM are added back into these expressions by using a Rouse chain with fixed ends. We find consistency in the friction used for both fast and slow modes. Using these analytic expressions, the polymer density, the molecular weight of a Kuhn step, Mk, and the low-frequency cross-over between the storage and loss moduli, G' and G", it is now straightforward to estimate model parameter values and obtain predictions over the experimentally accessible frequency range. Moreover it has previously been shown that the two static parameters can be obtained from primitive path analysis of molecular dynamics simulations. In this work, two ways are shown for obtaining the friction parameter (i) from atomistic simulations of short chains using the free-volume theory, and (ii) from atomistic simulations of entangled chains by scaling the chain center-of-mass mean-square displacement from the slip-link model to that of the atomistic simulation. Futhermore three standing challenges for molecular theories of polymers (i) predictions for uniaxial extension of star-branched polymer melts (ii) predictions for blends of star-branched and linear chains and (iii) predictions for normal stress differences in start-up of shear and followoing cessation are addressed here using the DSM. Additionally the DSM is used to predict the mechanical properties of a cross-linked polydimethylsiloxane (PDMS) network swollen with non-reactive entangled PDMS solvent. These successful predictions strongly suggest that the observed rheological modification in the swollen blend arises from the constraint dynamics between the network chains and the dangling ends.
Ph.D. in Chemical Engineering, May 2016
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Title: ENACTMENT OF COMMON CORE STATE STANDARDS FOR MATHEMATICS: RELATIONSHIP BETWEEN TEACHERS’ CHOICES OF CURRICULUM, TEACHING, AND PROFESSIONAL DEVELOPMENT
Creator: Kartal, Ozgul
Date: 2015, 2015-07
Description: In response to perceived problems of the United States mathematics curriculum, the Common Core State Standards (CCSS) were developed under the...
Show moreIn response to perceived problems of the United States mathematics curriculum, the Common Core State Standards (CCSS) were developed under the leadership of the National Governor Association (NGA) and the Council of Chief State School Officers (CCSSO), and were released in 2010. As of the time of this study, forty-four states, the District of Columbia, four territories, and the Department of Defense Education Activity have adopted the CCSS. The CCSS for Mathematics (CCSSM) initiative has raised many research questions for the field concerning the quality, enactment, and effectiveness and impact of the standards. There is a great deal of concern, in particular, about the enactment of the standards, because􀁿as pointed out by Heck, Weiss, and Pasley (2011)􀁿if standards have not been well implemented in a particular setting, then failure or ineffectiveness shouldn’t be blamed on the standards. Various researchers identified the key components of a successful enactment of a set of standards as curriculum, assessment, professional development, and teachers and teaching practice (e.g., Confrey & Krupa, 2010; Goertz, 2010; Weiss et al., 2002; Wu, 2011b). Therefore, this research study focused on the enactment of the CCSSM, and analyzed the curriculum, teaching, assessment, and teacher professional development as the key components of the enactment process. This study focused on the state of Illinois which is one of the states that started fully implementing the new academic standards in the 2013-14 school year, and hence had ample preparation and trial time between the adoption and full implementation years. This study investigated the alignment between teachers’ choices of curriculum and CCSSM, and relation between the curriculum resources, professional development, and enactment of CCSSM. The focus of the study was on the content of basic algebra and concepts of solving equations and slope while investigating the alignment of enactment of the CCSSM. The sample was comprised of twelve 9th grade algebra teachers from six different schools in the state of Illinois. The criteria in selecting the schools were the geographic location of the schools, the types of the schools, the curricula used at the schools, and the professional development on CCSSM offered at the schools. Results of this study found that the curricula have limited alignment with CCSSM, and that teachers’ enactment of mathematical practices was affected by the availability of variety of standards for mathematical practices in their curriculum as well as professional development opportunities. The curricula provided opportunities for various mathematical practice standards throughout the content of basic algebra, but some practice standards were left out. Teachers provided opportunities for a subset of the standards that were present in the instructional segments of their curriculum. If not, they provided opportunities for practice standards as a result of acquisition from professional developments. The impact of professional development was most evident when teachers using the same curriculum differed in their enactment of the practices. This study portrayed the relations between (low/high) enactments of CCSSM, curriculum resources (aligned or not aligned), and professional developments. Many states and districts are just beginning to incorporate CCSSM into their math curriculum at the time of this study. Therefore, the findings of this study will guide them as they make their textbook, curriculum, and professional development choices and decisions. In addition, this research generated valuable knowledge that would be useful not only in improving the enactment of the CCSSM, but also improving the enactment of future sets of standards. There are implications for curriculum designers, administrators/school and district leaders, professional development designers, and teacher educators.
Ph.D. in Mathematics Education, July 2015
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Title: RHEOLOGY OF ENTANGLED POLYMER LIQUIDS IN EQUIBIAXIAL ELONGATIONAL FLOWS
Creator: Mick, Rebecca M.
Date: 2015, 2015-05
Description: Equibiaxial deformation is an important flow in industrial processes such as film blowing and blow molding. Unfortunately, it is very...
Show moreEquibiaxial deformation is an important flow in industrial processes such as film blowing and blow molding. Unfortunately, it is very difficult to implement experimentally which has led to empirical design of these processes. A technique called continuous lubricated squeezing flow (CLSF) has been developed to perform equibiaxial deformation on systems such as polymer melts. This technique is used in this study to measure the behavior of entangled polymer melts in equibiaxial elongation to further the understanding of these materials in industrially relevant flows. The results of CLSF experiments on three linear chain polymer systems show strain softening for strain rates resulting in Weissenberg numbers, Wi = ε˙Bτd > 1. Higher rates lead to greater softening. The deviation from the linear viscoelastic (LVE) prediction occurs at about a strain of one for all the materials. Equibiaxial and shear behavior were compared for two monodisperse linear systems. When normalized by LVE behavior, the two flows yield similar behavior such that the equibiaxial rheology could be inferred from shear rheology. Unfortunately, polydisperse linear and branched systems did not show the same behavior. The two monodispere systems were compared to the GLaMM and Discrete Slip-Link molecular theories. Neither model could successfully predict the equibiaxial behavior; both predicted excessive strain softening and a premature deviation from LVE. Recent literature has suggested that based on uniaxial measurements, dilution changes the behavior of an entangled polymer system. This is contrary to theories of polymer dynamics. A pure melt and diluted melt with the same entanglement density were compared in shear and equibiaxial flows after adjusting for changes in friction. The results were consistent with universality principles of entangled polymers; the uniaxial results require further investigation.
Ph.D. in Chemical Engineering, May 2015
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Title: MARKOV SWITCHING MODELS OF POPULAR FOREIGN EXCHANGE CARRY TRADE STRATEGIES
Creator: Miller, Larissa J.
Date: 2016, 2016-07
Description: The nature of the carry trade produces periods of steady profitability and periods of extreme terror. The 1980s proved to be a particularly...
Show moreThe nature of the carry trade produces periods of steady profitability and periods of extreme terror. The 1980s proved to be a particularly profitable time period. However, during market crashes in the either equity or bond market, the carry trade is marked with short periods of substantial losses (Menkhoff, Saro, Schmeling, Scrimpf 2012). The global financial crisis of 2007 – 2008 was associated with large losses to carry trades. History repeatedly suggests these two bull and bear states in the economic environment (Fabozzi, Francis 1977). An additional state of market neutrality or stability could also be considered. The purpose of this dissertation is to develop a model of the carry trade with multiple states using the Markov switching methodology. To accomplish this, we use two different popular carry trade strategies: (a) logistic regression and (b) mean-variance optimization. As a benchmark, we include an equally weighted portfolio of long positions in foreign currencies against the dollar. We develop a single state model as well as a normal mixture model for each of the two carry trade strategies. The mixture models assume a static probability of the economy being in either state. However, the financial markets are not static. Applying a Markov chain allows us to build a dynamic model, which allows for new information to determine the probability of the next state. We applied a Markov chain to determine the probability of the current state and the next state to improve trading results. We found the application of a Markov chain did not improve trading performance. The portfolio consists of 12 different currencies including both mature and emerging markets. The training period for determining the weights is 1998 through 2002. Using daily data from 2002 through 2015, we evaluate the performance of each strategy using cumulative returns. These results demonstrate the periods of profitability followed by short periods of terror. Next we evaluate the performance of each strategy with an applied mixture-model. The mixture-model improves the results of each strategy. Applying a Markov chain allows for better determination of both the bear and bull states. We use only the two state environment as the three state environment was unstable.
Ph.D. in Management Science, July 2016
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Title: SECURE DATA SERVICE OUTSOURCING IN CLOUD COMPUTING
Creator: Wang, Cong
Date: 2012-04-22, 2012-07
Description: Cloud computing economically enables a fundamental paradigm of data service outsourcing, which provides lower up-front capital costs and less...
Show moreCloud computing economically enables a fundamental paradigm of data service outsourcing, which provides lower up-front capital costs and less hands-on management. However, outsourcing data services to the commercial public cloud deprives customers' control over the systems that manage their data, raising security and privacy as the primary obstacles to the adoption of the cloud. To address these challenges, in this dissertation we explore the problem of secure and privacy-assured data service outsourcing in cloud computing. We aim at deploying the most fundamental data services including data storage, search, and sharing on the commercial public cloud, with built-in security and privacy assurance as well as high level service performance, usability, and scalability. Our contributions are as follows: Firstly, we focus on privacy-preserving secure cloud storage auditing to maintain strong storage correctness guarantee, given the di culty that data les are no longer locally possessed by data owners. We rst develop a random-masking sampling approach to allow a third party auditor to perform on-demand privacy-preserving storage correctness auditing on behalf of data owners, without violating owners' data privacy. For storage correctness assurance with data dynamics, we further investigate a novel sequence-enforced Merkle Hash Tree and manipulate it with the random sampling approach to support fully dynamic data operations. Secondly, we focus on privacy-assured and e ective cloud data search services with strong privacy-assurance, while enjoying high service-level performance inherently demanded by the large number of data users and huge amount data les. We rst investigate a widely applicable fuzzy/similarity keyword search problem, and develop a brand new symbol-based trie-traverse searching approach, where transformed fuzzy keywords extracted from data les are stored using a multi-way tree structure, while protecting keyword privacy. To enable search result relevance ranking, we further investigate secure ranked search, which facilitates e cient server-side result ranking without leaking any keyword related information. Thirdly, we study how to enable scalable and owner-controlled cloud data sharing services, given the challenge that data no longer resides on owners' trusted domain. We rst associate data with a set of meaningful attributes, use logical composition of attributes to re ect ne-grained data access, and enforce owner's control via attribute-based encryption. For the inherent scalability requirement of cloud system, we further leverage the cloud as a mediated proxy, to which data owners can delegate most cumbersome data/user management workload, without a ecting the underlying data con dentiality.
Ph.D. in Electrical Engineering, July 2012
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Title: EMBEDDED SYSTEM DESIGN FOR TRAFFIC SIGN RECOGNITION USING MACHINE LEARNING ALGORITHMS
Creator: Han, Yan
Date: 2016, 2016-12
Description: Traffic sign recognition system, taken as an important component of an intelligent vehicle system, has been an active research area and it has...
Show moreTraffic sign recognition system, taken as an important component of an intelligent vehicle system, has been an active research area and it has been investigated vigorously in the last decade. It is an important step for introducing intelligent vehicles into the current road transportation systems. Based on image processing and machine learning technologies, TSR systems are being developed cautiously by many manufacturers and have been set up on vehicles as part of a driving assistant system in recent years. Traffic signs are designed and placed in locations to be easily identified from its surroundings by human eyes. Hence, an intelligent system that can identify these signs as good as a human, needs to address a lot of challenges. Here, ―good‖ can be interpreted as accurate and fast. Therefore, developing a reliable, real-time and robust TSR system is the main motivation for this dissertation. Multiple TSR system approaches based on computer vision and machine learning technologies are introduced and they are implemented on different hardware platforms. Proposed TSR algorithms are comprised of two parts: sign detection based on color and shape analysis and sign classification based on machine learning technologies including nearest neighbor search, support vector machine and deep neural networks. Target hardware platforms include Xilinx ZedBoard FPGA and NVIDIA Jetson TX1 that provides GPU acceleration. Overall, based on a well-known benchmark suite, 96% detection accuracy is achieved while executing at 1.6 frames per seconds on the GPU board.
Ph.D. in Computer Engineering, December 2016
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Title: INFLUENCE OF OWNER-ORGANIZATION IMPRESSION AND CONTRACT FRAMING ON CONSTRUCTION CONTRACTORS' RISK PERCEPTIONS
Creator: Hanioglu, Mehmet Nihat
Date: 2014, 2014-12
Description: In a construction project, it is generally accepted that the contractor's perceived risk is the main factor in determining what is to be...
Show moreIn a construction project, it is generally accepted that the contractor's perceived risk is the main factor in determining what is to be proposed as the project cost and duration. Both the owner-organization and the contractor are aware of the existing risks and the owner-organizations tend to mitigate the existing risks by using the construction contract. It is hypothesized that the contractor’s initial impression of the owner-organization is a factor in the contractor’s perception of risk. It is further hypothesized that the initial impression is influenced by the content and context of the construction bid documents, which further influences the perceived risk and the bid strategy. The goal is to investigate the factors that influence contractors' impression of the owner-organization and to study the effects of contract document language and content in the impression formation process and subsequent development of a bid strategy. By better understanding the factors and relationships that influence impression formation and risk perceptions, it is expected that substantial time, money and unnecessary contention between these parties can be eliminated.
Ph.D. in Civil Engineering, December 2014
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Title: CYCLIC THERMAL TREATMENT
Creator: Gu, Sijie
Date: 2015, 2015-12
Description: Cyclic thermal treatment has the potential to improve energy efficiency of thermal processing. It has been shown that in some cases, the...
Show moreCyclic thermal treatment has the potential to improve energy efficiency of thermal processing. It has been shown that in some cases, the productivity was enhanced by the cyclic thermal treatment operation. In order to investigate the cyclic thermal treatment effect, Copper-Nickel interdiffusion couples were investigated. When the Cu-Ni interdiffusion couple showed positive results, the cyclic thermal treatment was applied to pack carburization and gas carburization of steel. The Cu-Ni interdiffusion couples were annealed with different time-temperature profiles for 5 days. There are three types of time-temperature profile; isothermal, symmetric, and asymmetric cyclic thermal treatment. After thermal treatment, concentration-distance profiles were. Based on the concentration-distance profile, the interdiffusion coefficients of different time-temperature profiles were calculated. The interdiffusion coefficient of the diffusion couple with a ramp rate of 1°C/min had a higher diffusion coefficient than that of the diffusion couple annealed isothermally at the equivalent temperature, 863°C, which means that cyclic thermal treatment has the effect of accelerating diffusion. When the ramp rate was 5ºC/min interdiffusion coefficients were higher than that of the diffusion couple annealed isothermally at the maximum temperature. However, when the ramp rate was increased to 10°C/min, the diffusion coefficient decreased to almost the same as the interdiffusion coefficient of the diffusion couple at the equivalent temperature. After achieving a promising result for the Cu-Ni diffusion couples, we expanded the cyclic thermal treatment to carburizing. The temperature range for cyclic pack carburization was 850° to 950°C. Increasing the cyclic ramp rate resulted in an increase in the case depth. Due to the setup of the pack carburization, the maximum cooling rate achievable is 5°C/min. In order to reach a higher ramp rate, an induction heating gas carburization system was setup. The temperature range for the cyclic induction heat gas carburization was 850°C to 950°C. For the cyclic induction heat gas carburization with increase in ramp rate, the case depth increased. The sample induction gas carburized at a ramp rate of 20°C/min had a deeper case depth than the sample induction gas carburized isothermally at 904.4°C, the equivalent temperature. The first test showed the sample induction gas carburized with a ramp rate of 20°C/min had a deeper case depth than the sample induction gas carburized isothermally at 950° C. With this we draw the conclusion that the cyclic induction gas carburization can achieve a deeper case depth than the isothermal at equivalent temperature induction gas carburization.
Ph.D. in Materials Science and Engineering, December 2015
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Title: POWER GRID VERIFICATION ON CLOUD
Creator: Gupte, Naval
Date: 2016, 2016-05
Description: Reliability and performance of modern ICs is becoming increasingly susceptible to supply voltage variations. Increased demand for low voltage...
Show moreReliability and performance of modern ICs is becoming increasingly susceptible to supply voltage variations. Increased demand for low voltage integrated circuits has made power grid analysis extremely critical and indispensable in modern design flows. Efficient validation of on-chip power distribution network is computationally demanding because of increasing grid sizes. Power grid simulation is critical for analysis and verification of power supply noises for robust and reliable IC designs. Computational demands to simulate power grids for ICs with increasing complexity is never-ending. Cloud computing platforms can be leveraged to mitigate costs associated with making these resources available. However, since simulation data usually contains sensitive design information, simulating on third-party platforms lead to major security concerns. In this study, we propose a framework for secure power grid simulation on Cloud. A transformation algorithm to hide current excitations is presented, while still allowing a majority of computations to be completed on Cloud. We employ multiple compression strategies to significantly reduce communication and storage overheads. Experiments show that our framework can achieve similar turn-around time as an insecure simulator on Cloud, while securing current excitations and output voltage vectors with reasonable communication and computational overheads. Vectorless technique to grid verification estimates worst-case voltage noises without detailed enumeration of load current excitations. We study voltage noise assessment in RLC models of VDD and GND networks in integrated power grids. Abstract grid model is utilized to abbreviate runtime, while transient constraints capture transitory circuit behaviour. Heuristics are employed to extract constraints that restrict power consumption profiles to realistic scenarios. Multiple linear programming problems are formulated to evaluate bounds on voltage overshoots and undershoots. We propose ways to mitigate storage and computational requirements on processing resources, enabling users to deploy computations on economical Cloud Computing platforms. Recommended solution is parallelizable, thereby reducing the overall verification time. Data compression is applied to fully exploit the compute capabilities of contemporary processors for higher throughputs. Experimental results suggest that the proposed technique is practical and scalable for industrial grids.
Ph.D. in Electrical Engineering, May 2016
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Title: COMPUTER AIDED DIAGNOSIS IN MAMMOGRAPHY WITH CONTENT-BASED IMAGE RETRIEVAL
Creator: Jing, Hao
Date: 2011-11, 2011-12
Description: Computer-aided diagnosis (CAD) for breast cancer, a common form of cancer in women, has been an active research area. This work aims to...
Show moreComputer-aided diagnosis (CAD) for breast cancer, a common form of cancer in women, has been an active research area. This work aims to investigate and develop CAD techniques for clustered microcalcifications (MCCs), which can be an important early sign of breast cancer. The contributions of this work include development of a database of cancer cases and algorithms for detection and classification of MCCs. First, a database consisting of a large number of cases is built from different sources. To support the merging of cases from different data sources, a feature comparison study is conducted between mammograms from screen film and full field digital mammography (FFDM) systems. It is demonstrated that the features extracted from film and FFDM are highly correlated and there is no adverse effect on a CAD task of classification when used together. Second, a spatial point process (SPP) approach is proposed to exploit the spatial distribution among different MCs in a mammogram directly during the detection process. This is different from the conventional approach in which detection algorithms are employed to first identify individual MCs in a mammogram, which are subsequently grouped into clusters by a clustering algorithm. The performance of the proposed approach is demonstrated to be superior to an existing method based on the support vector machine (SVM). Third, in observation of the emerging of large databases from the picture archiving and communication (PAC) systems in the clinics, a retrieval driven approach is proposed for classification of MCCs. In this approach, for a case to be diagnosed (i.e., query), a set of similar cases is retrieved from a database and subsequently is used to train xii an adaptive classifier specifically for the query case using the technique of logistic regression. The proposed approach is demonstrated to lead to significant improvement in classification accuracy. Moreover, the proposed adaptive classification approach is further developed using regularization techniques, where a prior is first derived from a baseline classifier and then used to regularize the adaptive classifier trained with the retrieved cases. The regularized adaptive classifier can be more computationally efficient, and is demonstrated to achieve further improvement in performance.
Ph.D. in Electrical Engineering, December 2011
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Title: MEASUREMENT OF INTRARETINAL NITRIC OXIDE IN EARLY DIABETIC RETINOPATHY
Creator: Guthrie, Micah
Date: 2014, 2014-12
Description: Diabetic retinopathy (DR) is the most frequent cause of new cases of blindness among adults aged 20-74 years. Nearly all patients with Type 1...
Show moreDiabetic retinopathy (DR) is the most frequent cause of new cases of blindness among adults aged 20-74 years. Nearly all patients with Type 1 diabetes and greater than 60% of patients with Type 2 diabetes will develop retinopathy within the rst two decades of the disease. Nitric oxide (NO) has been shown to play a role in the progression of DR, contributing to neuronal dysfunction and the breakdown of the blood-retina barrier early stages of the disease. The objective of the current study was to investigate the changes in intraretinal NO levels in early DR. To accomplish this, a dual NO/electroretinogram (ERG) electrode was developed to make the rst direct measurements of NO concentration throughout the in vivo retina. These electrodes were validated in an in vivo animal model by comparing control recordings to those taken after injection of the broad spectrum nitric oxide synthase (NOS) inhibitor L-NG-Nitroarginine methyl ester (L-NAME). Control NO pro les showed high levels of NO in the photoreceptor layer with localized areas of increased NO in the amacrine/ganglion cell layer. L-NAME NO pro les showed substantially reduced NO in the retina, indicating that the electrodes were measuring actual NO. The electrodes were then used to record NO pro les from the retinas of rats made diabetic with streptozotocin (STZ). The recordings were obtained three weeks after injection of STZ. Blood glucose levels were also monitored in order to correlate the blood glucose level with intraretinal NO concentration. It was found that mild diabetic rats (blood glucose 250-400 mg/dL) had higherthan- control levels of NO throughout their retinas. Severe diabetics (500-600 mg/dL) had lower-than-control levels, while moderate diabetics (400-500 mg/dL) did not have signi cantly di erent NO levels than controls. The NO pro les from the severe diabetics were very similar to L-NAME pro les, indicating that NOS production may be abnormal in severe diabetics. It was also found that intraretinal NO concentration was inversely correlated with the blood glucose of diabetic rats. To determine if the changes in NO seen in diabetic rats were due to direct tissue exposure to high glucose, NO pro les were also recorded from rats acutely injected with glucose solution to achieve similar levels of hyperglycemia. No changes in NO levels were seen in the retinas of these acute hyperglycemic rats, indicating that there are other factors besides high glucose contributing to the NO changes in DR. The results show that there is not a simple increase in NO as severity of diabetes increases and highlight the importance of being able to make measurements of bioavailable NO in retinal tissue. The electrodes were able to detect clear di erences in experimental DR, indicating their utility in investigating NO changes in the early stages of the disease. Future work with the electrodes needs to be performed to investigate the mechanisms of NO changes in DR in order to develop potential treatments which could mitigate the damage at an early stage before vision loss occurs.
M.S. in Biomedical Engineering, December 2014
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Title: TOWARD A NATURAL GENETIC/EVOLUTIONARY ALGORITHM FOR MULTIOBJECTIVE OPTIMIZATION
Creator: Ramasamy, Hariharane
Date: 2013, 2013-05
Description: Practical optimization problems often have multiple objectives, which are likely to conflict with each other, and have more than one optimal...
Show morePractical optimization problems often have multiple objectives, which are likely to conflict with each other, and have more than one optimal solution representing the best trade-offs among the competing objectives. Genetic algorithms, which optimize by repeatedly applying genetic operators to a population of possible solutions, have been used recently in multiobjective optimization, but often converge to a single solution that is not necessarily optimal due to lack of diversity in the population. Current multiobjective genetic and other evolutionary methods prevent this premature convergence by promoting new members that are dissimilar in parameter or objective space. A distance measure, which calculates similarities among the members in either objective or parameter space, is used to degrade the fitness of solutions when they are crowded in a small region. This process forces the algorithm to find new but distinct trade-off points in the objective or parameter space, but is computationally expensive. As the number of objectives or parameters increases, the methods fail to scale up and they deviate from the motivating concept of the genetic algorithm—natural evolution. We extend the standard genetic algorithm through two simple, yet powerful, changes motivated by natural evolution. In the first method, the algorithm, at each step, randomly or sequentially chooses one of the objectives for optimization; hence the method is called sequential extended genetic algorithm (SEGA). In the second method, a population is maintained for each objective, and crossover is performed selecting parents from across populations. This method is called parallel extended genetic algorithm (PEGA). We applied these methods to test problems from the literature, and to two well known problems, protein folding and multiple knapsack. We discovered our methods found better trade-off solutions than current multiobjective methods, without increasing computational complexity of genetic algorithms.
PH.D in Computer Science, May 2013
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Title: POLARIZATION COUPLING IN SEMICONDUCTOR NANO-DIMERS IN THE TERAHERTZ RANGE
Creator: Hu, Zhijing
Date: 2017, 2017-05
Description: Surface plasmon resonance (SPR) occurs at the interface of a semiconductor and a dielectric when certain conditions are satisfied. SPR is...
Show moreSurface plasmon resonance (SPR) occurs at the interface of a semiconductor and a dielectric when certain conditions are satisfied. SPR is impetus to new sensor and device development in the optical range, with nanoparticles of noble metals taking up major roles. Typical conduction band electron concentrations in semiconductors lead to resonance frequencies in the terahertz and infrared bands. While the response strength is weaker than those exhibited by metals, it can be made up for by the formation of aggregates. The added degree of freedom by doping or carrier injection further enhances the versatility of semiconductor nanoclusters. To obtain a first principle solution to the coupled set of equations for charge carrier transport and electrodynamics in a conductive cluster is a formidable task with a high computational cost. Employing a finite-element based tool, the COMSOL Multiphysics Simulation Software, the interaction inside and outside some elementary semiconductor structures such as slab and sphere have been solved, which revealed the screening of the internal field while displaying dispersion and absorptions effects. The study of semiconductor dimer also showed a significant field enhancement and frequency shift. Under strong applied field, asymmetric polarization within the particles is revealed. The accompanying nonlinear polarization response can be employed to develop new devices. These model structures can serve to provide insight to the analysis and synthesis more complex structures.
Ph.D. in Electrical Engineering, May 2017
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Title: A NANO-STRUCTURED CERAMIC/POLYMER COMPOSITE FILM FOR ELECTRONIC INTERCONNECTIONS
Creator: Harwath, Frank
Date: 2016, 2016-05
Description: Separable electrical interconnections are a ubiquitous part of modern life and for technical reasons are currently based on the use of gold....
Show moreSeparable electrical interconnections are a ubiquitous part of modern life and for technical reasons are currently based on the use of gold. Since gold is a commodity and subject to significant price fluctuations there is a need for separable interconnects not based on gold. Polymer/ceramic films were produced from various polymer precursors with loadings of multi-wall nanotubes (MWNT) and inert fillers. A variety of applications means were employed with the best success being achieved by means of a modified doctor blade. Pyrolysis was conducted in an inert atmosphere at 1 bar at a range of temperatures in a tube furnace. Pyrolysis was also conducted using a fiber laser. The modulus of the film is estimated to be 71.8 MPa with an ultimate tensile strength of 179 MPa based on hardness tests and anisotropic crack dimensions which developed as a result of uniaxial stress induced during application of the precursor. Uniaxial stress improved film adhesion regardless of filler type or level. Modification of film characteristics after pyrolysis was attempted using spark plasma sintering (SPS). Electrical testing displayed a percolation threshold above loadings of 1% (wt) of MWNTs where there is a significant drop in electrical resistivity. Further reductions in contact resistance were demonstrated up to 2% loading of MWNTs. The level of contact resistance achieved (<10) for a separable contact, in conjunction with a gold plated contact representative of most electronic connectors, indicates that an acceptable level of contact resistance may be achieved using these materials. Characterization of the film using attenuated total reflectance (ATR), xray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy point to a morphology which is dominated by crystallites joined by regions of aliphatic carbon chains. Work function measurements were consistent with highly ordered pyrolytic graphite. (HOPG)
Ph.D. in Materials Science and Engineering, May 2016
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Title: FROM EXPLORATION TO RATIONAL DESIGN OF SELECTIVE PROPANE DEHYDROGENATION CATALYSTS
Creator: Hu, Bo
Date: 2015, 2015-12
Description: Light olefins, e.g., ethene and propene, are important building blocks of chemical industry for the production of fuels, polymers, lubricants...
Show moreLight olefins, e.g., ethene and propene, are important building blocks of chemical industry for the production of fuels, polymers, lubricants and other fine chemicals. Due to the rapidly increasing production of shale gas, conversion of small alkanes in the shale gas, e.g., ethane and propane, to their corresponding olefins via alkane dehydrogenation could be an important industrial process. This thesis has focused on exploring the novel single site heterogeneous catalysts for selective alkane dehydrogenation and investigating the general principles of rational catalyst design to achieve a better performing (e.g., more active, more stable, highly selective) dehydrogenation catalyst. Based on the observed reactivity of ZnO for olefin hydrogenation and activity of Zn-ZSM-5 catalysts for alkane activation, catalytic properties of isolated Zn2+ were first explored for propane dehydrogenation. The 3-coordinate Zn in single site Zn/SiO2 catalyst was demonstrated to be the catalytically active species that was highly selective for the generation of propene by propane dehydrogenation. DFT calculations revealed that slow β-hydride elimination of alkyl intermediates limited the overall activity of single site Zn/SiO2 catalyst. Thus, single site Co/SiO2 was also prepared in order to take the advantage of fast β-hydride elimination. The higher activity of single site Co/SiO2 emphasized the potential of transition metals for alkane dehydrogenation, and propane dehydrogenation reactivity of transition metals was further explored by investigating single site Fe/SiO2 catalyst. By comparing with metallic Fe nanoparticles and bulk phase Fe oxides catalysts, the 3-coordinate single site Fe2+ was also suggested to be the catalytically active species for selective propane dehydrogenation. However, the catalytic activity of single site Fe/SiO2 catalyst was lower than that of Zn/SiO2. Such result suggested heterolytic cleavage of C-H bonds was slow for transition metals, e.g., Co and Fe, due to their weak Lewis acidity, and it may mitigate the advantages gained in rapid β-hydride elimination. An exploration of ligand effects for improving heterolytic cleavage over single site heterogeneous catalysts was performed. The strength of metal oxygen bond governed by ligand electron donating effects and ligand basicity were found to be the critical chemical descriptors for a facile heterolytic cleavage. Those observed principles of ligand effects would lead to a new strategy of rational catalyst design for a superior dehydrogenation catalyst.
Ph.D. in Chemistry, December 2015
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Title: THE EFFECT OF NANOPARTICLE SELF-STRUCTURING ON WETTING AND SPREADING OF NANOFLUIDS ON SOLID SURFACES
Creator: Kondiparty, Kirtiprakash
Date: 2011-11, 2011-12
Description: Nanofluids are suspensions of nanometer-sized particles in liquids. The nanoparticles self-structure at the three-phase contact region...
Show moreNanofluids are suspensions of nanometer-sized particles in liquids. The nanoparticles self-structure at the three-phase contact region resulting in the structural disjoining pressure gradient which causes enhanced the spreading of nanofluids compared to simple fluids without nanoparticles. In this thesis, we attempt to understand the effect of the structural disjoining pressure on the spreading dynamics of nanofluids on solid surfaces. We observed nanoparticle self-structuring phenomena during film thinning on a smooth hydrophilic glass surface using a silica-nanoparticle aqueous suspension and reflected light interferometry. Our experiments revealed that film formed from small drop is thicker and contains more particle layers than a film formed from large drop. The data for the film-meniscus contact angle verses film thickness were obtained and used to calculate the structural energy isotherm of an asymmetric film. We studied the effect of structural disjoining pressure on the wedge meniscus profile formed by an oil drop on solid surface surrounded by nanofluid using Laplace Equation augmented with the structural disjoining pressure. Our analyses indicate that a suitable combination of the nanoparticle concentration, nanoparticle size, contact angle, and capillary pressure can result not only in the displacement of the three-phase contact line, but also in the spontaneous spreading of the nanofluid as a film on solid surface. We validated our theoretical predictions using experiments where we observed spreading of nanofluid on glass surface displacing a sessile drop of canola oil. The dynamic spreading of the nanofluid on a solid surface between a sessile oil drop on solid surface was experimentally measured using reflected light microscopy. We xiv obtained the rate of nanofluid spreading by plotting the position of the inner contact line with time. The nanofluid film was found to spread at a constant velocity. We modeled the spreading dynamics of the nanofluid film using the lubrication approximation of the Navier-Stokes Equation, taking into consideration the structural disjoining pressure in the over-all pressure balance. The model was evaluated by estimating the rate of nanofluid spreading for the 10v% nanofluid. The rate of spreading thus predicted by the dynamics model for 10v% nanofluid was in good agreement with the experimental observations.
Ph.D. in Chemical Engineering, December 2011
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Title: NEUROPATHOLOGIC CORRELATES OF BRAIN MACROSTRUCTURE
Creator: Kotrotsou, Aikaterini
Date: 2014, 2014-07
Description: Alzheimer’s disease, the most common form of dementia, is a degenerative disorder of the brain that leads to memory loss. Clinical diagnostic...
Show moreAlzheimer’s disease, the most common form of dementia, is a degenerative disorder of the brain that leads to memory loss. Clinical diagnostic techniques in use today rely on mental and behavioral tests and physical examinations and only provide diagnoses of possible or probable Alzheimer’s disease. However, lately it has become clear that clinical-pathological correspondence is not always consistent. A definitive diagnosis of Alzheimer’s disease is only possible via histology, when the density of neurofibrillary tangles and amyloid plaques is measured. Therefore, the development of a reliable neuroimaging technique that allows detection of Alzheimer’s pathology during life is needed. This method would be noninvasive, and could allow the detection of Alzheimer’s disease in the early stages, and could be also used to monitor the progression of the disease through time. The purpose of this work was to investigate the use of magnetic resonance imaging (MRI) as diagnostic tool for Alzheimer’s pathology and other age-related neurodegenerative pathologies that are common in older persons. To uncover the anatomical origins and determine the macrostructural signatures of age-related neuropathologies, it is necessary to link MRI findings with pathologic information on the same individuals. In this work, we focused on imaging cerebral hemispheres ex-vivo, when a complete pathology report was available from a board-certified neuropathologist. The main difference between this work and any other study is the abundance of postmortem imaging data paired with neuropathology data in a relatively large pool of subjects. First, we developed and validated a protocol to perform ex-vivo MR volumetry. By using this protocol we observed the longitudinal behavior of the volume of different brain regions. Furthermore, we tested the hypothesis that volumetric measurements performed ex-vivo are associated with in-vivo measurements. It was shown that: (a) regional brain volumes measured with this approach for ex-vivo MR volumetry remain relatively unchanged for a period of 6 months postmortem, and (b) a linear correspondence was detected between in-vivo and ex-vivo measurements, suggesting that this approach captures information linked to antemortem macrostructural brain characteristics. Using the approach for ex-vivo MR volumetry, we combined ex-vivo MR volumetry with pathology on the same adults. AD pathology was significantly negatively correlated with volumes of cortical gray matter regions, mainly in the temporal, frontal, parietal and cingulate cortices, subcortical gray matter, and whole-hemisphere white matter. A significant negative correlation was shown between hippocampal sclerosis and volumes of the hippocampus, as well as other temporal and frontal gray matter regions. Finally, we performed a morphometric MRI study to investigate associations of brain volumes with pathology using voxel-based analysis. This technique allows the assessment of gray and white matter volumes in subjects with different pathologies compared with controls in an automated fashion, across the whole brain. AD pathology was negatively associated with regions of gray matter and white matter located in temporal and frontal lobes, and orbitofrontal cortex. This work examined the associations of brain volumes with Alzheimer’s pathology and other typed of age-related neurodegenerative pathologies. Combining histological result with MR images requires that the time elapsed between imaging and histology is minimal. Ex-vivo MRI provides images at essentially the same time-point as histological examination of the tissue, and this study is unique in that it involves a large number of cadaveric brain hemispheres. The findings of this ex-vivo study could allow for future standardization of MRI as a biomarker of neurodegenerative diseases, and also allow in identification and classification of subjects in groups for tests of new drugs.
Ph.D. in Biomedical Engineering, July 2014
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Title: DEVELOPMENT OF ADVANCED PACKAGING, FABRICATION AND RELIABILITY METHODS FOR SUBMINIATURE IMPLANTABLE NEURAL PROSTHESES
Creator: Kim, Taehyung
Date: 2011-08, 2011-07
Description: The main purpose of the present thesis is to study the critical reliability issues of polymeric encapsulated electronic devices for visual...
Show moreThe main purpose of the present thesis is to study the critical reliability issues of polymeric encapsulated electronic devices for visual prosthesis. Visual prosthesis has been compatibly studied over twenty years in many professional research labs. The electric design of circuit for the visual prosthesis has been well studied so far. However, the device packaging design and reliability have been not studied extensively. In particular, failure analysis and reliability using non-hermetic packaging for long lifetime visual prosthesis have been poorly studied. The first step of the research for this thesis was to create a mechanical design of a visual prosthesis prototype. The prototype device was created by fabricate a multi-layer structure consisting of electrodes, substrate, and integrated circuit chip with silicone encapsulated packaging. The interconnection between the chip and electrodes used Au wire and Al bonding pad. The prototype devices were tested in a liquid water. This water environment is not a common reliability test for commercial electronic packaging. Relative humidity testing is a common and widely used testing methods, but the visual prosthesis device cannot be applied to gas phase relative humidity testing due to the environment condition. Water absorption in polymeric material in the liquid water is higher than in the vapor water. After water penetrated interconnection interface, the Au-Al intermetallic compound becomes oxidized and generates bonding die open failure. From these unusual testing results, we were conformed the failure mechanism and predicted the lifetime using Au-Al imtermetallic growth pattern and oxidation. Additional discussions include transition metal ions in CSF to expect the other failure mechanisms. Wafer and packaging level xiii failure mechanisms by Cu and Fe ions are also discussed in this thesis. The end of this thesis discuss possible fabrication processing to protect overall external environment effects for polymeric packaging visual prosthesis. Overall this thesis study, which uses polymeric packaging electronic devices for bio-implant research, concluded that devices may not make good reliability devices in the CSF environment. The corrosion, oxidation and metallization on or in metal surfaces and interconnection interfaces should continually be studied to produce longer lasting electronic devices over 30 years. The reliability of the visual prosthesis has not been well studied in any other professional research labs, so this thesis may give or address some initial guidelines to help save time for the project decision in the future to develop advanced hermetic packaging for bioimplantable electronic devices.
Ph.D. in Materials Science and Engineering, July 2011
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