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Title: AN ENERGY-PRESERVING SCHEME FOR THE POISSON-NERNST-PLANCK EQUATIONS
Creator: Kabre, Julienne
Date: 2017, 2017-07
Description: Transport of ionic particles is ubiquitous in all biology. The Poisson-Nernst- Planck (PNP) equations have recently been used to describe the...
Show moreTransport of ionic particles is ubiquitous in all biology. The Poisson-Nernst- Planck (PNP) equations have recently been used to describe the dynamics of ion transport through biological ion channels (besides being widely employed in semiconductor industry). This dissertation is about the design of a numerical scheme to solve the PNP equations that preserves exactly (up to roundoff error) a discretized form of the energy dynamics of the system. The proposed finite difference scheme is of second-order accurate in both space and time. Comparisons are made between this energy dynamics preserving scheme and a standard finite difference scheme, showing a difference in satisfying the energy law. Numerical results are presented for validating the orders of convergence in both time and space of the new scheme for the PNP system. The energy preserving scheme presented here is one dimensional in space. A highlight of an extension to the multi-dimensional case is shown.
Ph.D. in Applied Mathematics, July 2017
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Title: INVESTIGATION OF PERFORMANCE AND DURABILITY OF POLYMER ELECTROLYTES FOR ELECTROCHEMICAL ENERGY STORAGE AND CONVERSION TECHNOLOGIES
Creator: Jung, Min-suk
Date: 2016, 2016-07
Description: Polymeric ion exchange membranes are integral components of electrochemical conversion/storage devices such as fuel cells, water electrolyzers...
Show morePolymeric ion exchange membranes are integral components of electrochemical conversion/storage devices such as fuel cells, water electrolyzers, and redox flow batteries. There has been dramatic progress in the research and development of cation exchange membranes (CEM). Nafion® (perfluorosulfonic acid membranes) is one example of a state-of-the-art CEM and has been successfully demonstrated in various electrochemical energy devices. Unlike CEMs, anion exchange membranes (AEMs) have been of limited utility to date due to their drawbacks, including poor chemical/mechanical stability and low ionic conductivity. However, alkaline environments result in better activity for electrochemical reactions and afford the possibility of using non-platinum group metal (PGM) electrocatalysts. AEMs, therefore, are still being studied in order to resolve existing challenges in terms of conductivity and stability in alkaline media and in strongly oxidizing solutions. In this work, AEMs derived from different types of polymer backbones were prepared, and their chemical stability and electrochemical property were investigated. Polysulfone (PSF) AEMs were prepared by first chloromethylating polysulfone, then by functionalizing chloromethylated polysulfone (CMPSF) with different base reagents. PSF-trimethylamine (TMA) AEMs showed a 40-fold reduction in vanadium (IV) ion (VO2+) permeability when compared to a Nafion® membrane and exceptional oxidative stability after exposure to a 1.5 M vanadium (V) ion (VO2 +) solution for 90 days. PSF-TMA AEMs were successfully demonstrated in the all-vanadium redox flow battery. Excellent energy efficiencies (>75 %) were attained and sustained over 75 chargedischarge cycles for a vanadium redox flow battery prepared using the PSF-TMA separator. Crosslinking of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) AEMs using diamine was tried with intentions to improve the mechanical stability and electrochemical property of PPO AEM. Crosslinked PPO AEMs (30 ± 4 % at 25 oC) showed less liquid water uptake than non-crosslinked PPO AEMs (46 ± 5% at 25 oC) while maintaining comparable ionic conductivities (hydroxide ion conductivity of 45 mS/cm at 60 oC). Crosslinked PPO AEMs maintained mechanical integrity and still showed some mechanical stability (ultimate tensile strength of 3~4 MPa and elongation at break of 13~17 %) after exposure to 1 M KOH at 60 oC for 14 days, while noncrosslinked PPO AEMs completely lost their mechanical durability. Finally, this dissertation presents research related to perfluorinated AEMs prepared using a Grignard reagent. These membranes exhibited 0.7 mmol/g of Cl- ion exchange capacity (IEC), 20 mS/cm of hydroxide ion conductivity at 20 oC, and 10 % of water uptake at room temperature. The membranes also maintained 90 % of their initial conductivity after an exposure to 1.5 M VO2+ in 3 M H2SO4 solution for seven days.
Ph.D. in Chemical Engineering, July 2016
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Title: LOAD ANALYSIS BASED ON MACHINE LEARNING IN POWER SYSTEMS
Creator: Lu, Dan
Date: 2017, 2017-05
Description: The dissertation is composed by four parts, first, load sampling for SCUC based on Principal Component Analysis (PCA) and Kernel Density...
Show moreThe dissertation is composed by four parts, first, load sampling for SCUC based on Principal Component Analysis (PCA) and Kernel Density Estimation (KDE); second, load forecasting based on PCA and Bayesian ridge regression; third, anomalies detection based on Machine Learning methodology; fourth the long-term planning of Battery-based Energy Storage Transportation (BEST) in power system. Mathematical models are constructed to fulfill the research of the three targets, and numerical examples are used to test the models. The first three parts are based on PCA, which reduced the load dimensions. In the first part, a robust power system Unit Commitment (UC) is the aim to fulfil the possible load. In the second part, a novel short-term nodal load forecasting is raised to give better prediction of the next day load to improve the next data UC scheduling. In the third part, anomalies are detected in the reduced power flow space based on the pattern identified in the lower dimensional space. The purpose of the fourth part is to find ways of better utilizing the existing resources from integrating the frontier technology, the mobility of more compact and higher capacity batteries. Mix-integer programming (MIP) is used in the formulation.
Ph.D. in Electrical Engineering, May 2017
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Title: THE TEMPORAL RELATIONSHIP BETWEEN DEPRESSION AND THE CONVERSION TO DEMENTIA: A RETROSPECTIVE ANALYSIS
Creator: Rog, Lauren
Date: 2011-07, 2011-07
Description: A relationship between depression and the dementing process has been fairly well established in both patients with mild cognitive impairment ...
Show moreA relationship between depression and the dementing process has been fairly well established in both patients with mild cognitive impairment (MCI) and dementia (e.g., Apostolova and Cummings, 2008; Lyketsos et al., 2002; Starkstein et al., 2005). However, less clear is the temporal role depression plays in the dementing process, with the possibilities including depression as a risk factor, a prodrome, or a consequence of dementia. Variables that have been considered to affect this relationship include gender, depression severity, lifetime history of depression, and etiology of cognitive decline. The current study examined the temporal relationship between depression and dementia in a sample of 218 patients with MCI or dementia who were seen for at least one follow-up visit at the neuropsychology service of an urban university medical center. Results did not reveal support for either the prodrome or the risk factor hypothesis of the depression-dementia relationship. However, it was found that people with a past history of depression who did not show depressive symptoms concurrent with their cognitive decline converted most quickly to dementia, suggesting a unique depression-dementia relationship in people with earlier-life depression.
Ph.D. in Clinical Psychology, July 2011
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Title: STEREO-BASED DEPTH MAP PROCESSING: ESTIMATION AND REFINEMENT
Creator: Loghman, Maziar
Date: 2016, 2016-12
Description: During the past decade, research in 3D video has become a hot topic owing to advancements in both hardware and software. Amongst different...
Show moreDuring the past decade, research in 3D video has become a hot topic owing to advancements in both hardware and software. Amongst different methods proposed for representing 3D data, multi-view video plus depth (MVD) format has gained a lot of attention. Most of such 3D algorithms rely on a per-pixel depth representation of the scene called a depth map. Depth maps are very useful for rendering virtual views and have lead to advancements in 3D compression algorithms. Generating an accurate and dense depth map is one of the important prerequisite for many 3D video applications. In this thesis, we highlight the following major problems in MVD. * Depth map estimation * Depth map refinement * Depth map coding In order to generate an accurate depth map, we propose a method based on Census transform with adaptive window patterns and semi-global optimization. A modified cross-based cost aggregation technique is proposed which helps to calculate a more reliable depth map. In order to further enhance the quality of the generated depth map, a novel multi-resolution anisotropic diffusion based algorithm is presented. The proposed depth refinement algorithm computes a dense depth map in which the holes have been filled and the object boundaries are sharpened. The next part of the research is based on depth map coding. In depth map coding, a considerable amount of time is required to investigate the mode decision pro- cess for every block of depth pixels. However, in real-time purposes, we can partially skip the mode selection step. In this thesis, we propose a novel depth intra-coding scheme for 3D video coding based on HEVC standard. The core idea of the proposed method is motivated by the fact that depth maps have specific characteristics that distinguish them from those of color images. By analyzing the reference depth maps based on homogeneousness of different regions, for some particular blocks, the DMM full-RD search is skipped and the mode is selected based on the previous similar tree- blocks. By this means, the time complexity of the encoding process is significantly reduced.
Ph.D. in Electrical Engineering, December 2016
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Title: MAXIMIZATION OF SYSTEM UTILITY VALUE FOR TIME-SENSITIVE APPLICATIONS
Creator: Li, Shuhui
Date: 2014, 2014-12
Description: Many applications are time-sensitive in the sense that the usefulness or the quality of their end results depends on their completion time....
Show moreMany applications are time-sensitive in the sense that the usefulness or the quality of their end results depends on their completion time. Examples of this type of applications are threat detections in air defense systems [97], radar trackings [36, 85], mobile navigations by Google [79, 44], and online gaming by Nintendo [38], to name a few. Take the threat detection application as an example, clearly, the earlier a threat is detected, the higher utility the application provides, as earlier detection provides more time to eliminate the threat [97]. This demonstrates the time-sensitivity of its utility. Here, the term `utility' means the actual bene t that accrues from the delivery of services [16]. The dependence between an application's accrued utility and its completion time is often modeled by a Time Utility Function (TUF). Apparently, when a system has multiple time-sensitive applications competing for the resources, a question arises: how to schedule their execution orders such that the system can yield maximal accrued utility? This thesis is to address the question. In this thesis, two categories of scheduling problems for time-sensitive applications are investigated: single-task applications in uni-processor systems and parallel multi-task applications in multi-processor systems. For the rst category, a two-TUF application model with given execution time is introduced and two scheduling algorithms for this model are proposed. Di erent from the conventional one-TUF model which only considers the gain utility, the developed model can deal with both the gain and the penalty utilities. The model is further extended to cope with applications whose exact execution times are not known at a priori, rather only their probabilistic execution time distributions are known. For applications with variable execution times, the di culty is how to make judicious decisions about when to start, continue or abort the applications. For the second category, i.e., for parallel multi-task applications in multi-processor systems, di erent from the widely investigated sequential multi-task applications, a parallel multi-task application's execution can have both spatial and temporal in uence on other applications. We propose a metric to measure the spatial-temporal interference among parallel multi-task and time-sensitive applications with respect to accrued utility. Based on the metric, a 2-approximation algorithm is introduced for systems operate in discrete time domains and its lower bound of system total accrued utility value is proved. We also develop a heuristic scheduling algorithm to maximize system's total accrued utility value for continuous time systems. Finally, the thesis discusses how methodologies developed in the thesis can be applied to reduce system's operational cost without sacri cing applications' quality of service. We propose a model to bridge together two orthogonal scheduling criteria, i.e., the system operational cost and application response time, and solve the problem by transforming it to a system accrued utility value optimization problem. The research uses both theoretical and experimental approaches. Theorems and lemmas are developed to provide the foundations for our solutions, and at the same time, extensive experiments are conducted to empirically evaluate the performances of the developed solutions.
Ph.D. in Computer Science, December 2014
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Title: UNMANNED AIRCRAFT SYSTEM SENSE AND AVOID INTEGRITY AND CONTINUITY
Creator: Jamoom, Michael B.
Date: 2016, 2016-05
Description: This thesis describes new methods to guarantee safety of sense and avoid (SAA) functions for Unmanned Aircraft Systems (UAS) by evaluating...
Show moreThis thesis describes new methods to guarantee safety of sense and avoid (SAA) functions for Unmanned Aircraft Systems (UAS) by evaluating integrity and continuity risks. Previous SAA e↵orts focused on relative safety metrics, such as risk ratios, comparing the risk of using an SAA system versus not using it. The methods in this thesis evaluate integrity and continuity risks as absolute measures of safety, as is the established practice in commercial aircraft terminal area navigation applications. The main contribution of this thesis is a derivation of a new method, based on a standard intruder relative constant velocity assumption, that uses hazard state estimates and estimate error covariances to establish (1) the integrity risk of the SAA system not detecting imminent loss of “well clear,” which is the time and distance required to maintain safe separation from intruder aircraft, and (2) the probability of false alert, the continuity risk. Another contribution is applying these integrity and continuity risk evaluation methods to set quantifiable and certifiable safety requirements on sensors. A sensitivity analysis uses this methodology to evaluate the impact of sensor errors on integrity and continuity risks. The penultimate contribution is an integrity and continuity risk evaluation where the estimation model is refined to address realistic intruder relative linear accelerations, which goes beyond the current constant velocity standard. The final contribution is an integrity and continuity risk evaluation addressing multiple intruders. This evaluation is a new innovation-based method to determine the risk of mis-associating intruder measurements. A mis-association occurs when the SAA system incorrectly associates a measurement to the wrong intruder, causing large errors in the estimated intruder trajectories. The new methods described in this thesis can help ensure safe encounters between aircraft and enable SAA sensor certification for UAS integration into the National Airspace System.
Ph.D. in Mechanical and Aerospace Engineering, May 2016
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Title: NOVICE HIGH SCHOOL SCIENCE TEACHERS: LESSON PLAN ADAPTATIONS
Creator: Scharon, Aracelis Janelle
Date: 2013, 2013-05
Description: The Next Generation Science Standards (NRC, 2013) positions teachers as responsible for necessary decision making about how their intended...
Show moreThe Next Generation Science Standards (NRC, 2013) positions teachers as responsible for necessary decision making about how their intended science lesson plan content supports continuous student science learning. Teachers interact with their instructional lesson plans in dynamic and constructive ways. Adapting lesson plans is complex. This process of adapting lesson plans may play an important role in affording and constraining teachers’ actions and students’ learning (Brown, 2009). This study explored how five novice chemistry teachers (under 4 years of total teaching experience) at five Midwestern high schools adapted or retained their honors chemistry instructional lesson plans, and what associated contextual factors influenced their decisions. Using a case study design, this study was conducted during the fall semester of 2013 when teachers were focusing on introductory chemistry topics. Three frameworks (pedagogical content knowledge (PCK), teacher decision making, and pedagogical discontentment and self-efficacy) were used to investigate the relationships between teacher adaptations, contextual factors and decision making. The outcome of this study was the identification of 15 types of adaptations and 17 relevant contextual factors. Contextual factors were categorized by factors that relate to students or the teacher. Adaptations were categorized into three overarching types of adaptations. Lesson plan adaptations and contextual factors are discussed in the context of research on teacher decision making and lesson plan adaptations.
PH.D in Science Education, May 2013
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Title: ANALYSIS OF LOW DIMENSIONAL MAGNETIC SYSTEMS CONTAINING CHROMIUM(III) AND COBALT(II) LIGATED BY THE SQUARATE LIGAND: MAGNETIC CHARACTERIZATION, BIOLOGICAL CHARACTERIZATION, INSTRUMENTAL DEVELOPMENT, AND SOFTWARE DEVELOPMENT
Creator: Mcneely, James Halley
Date: 2013, 2013-07
Description: A large series of Chromium(III) and Cobalt(II) complexes containing the C4O4 (squarate) ligand have been synthesized and characterized...
Show moreA large series of Chromium(III) and Cobalt(II) complexes containing the C4O4 (squarate) ligand have been synthesized and characterized magnetically. These complexes include simple dimeric Cr(III) systems that display a wide range of isotropic exchange couplings. One of these dimers shows interesting biological activity pertaining to the cellular uptake of glucose. This same compound also enhanced proton relaxation in T1 and T2 NMR studies. Computational work done on these dimeric systems showed excellent agreement with experimental results, and was used to confirm the structure of the complexes. The effect of the bridging squarate ligand was also studied computationally. The squarate ligand significantly contributed to the exchange coupling in the dimeric systems, and was shown to behave countercomplementary to the μ-hydroxo bridges. This is the first explicit observation of countercomplementarity in Chromium(III) systems. Co3(OH)2(C4O4) · 3H2O, a cobalt chain structure featuring an interesting low temperature spin-idle phase, was also synthesized. It was found that based on storage conditions, this compound either stays stable after grinding or transforms into the structure Co(C4O4)(H2O)2. In addition, grinding the sample shows an out-of-phase maxima at ≥6 K that has a frequency dependence characteristic of a spin glass. A new software package was also developed to simulate Electron Paramagnetic Resonance (EPR) spectra using full numerical diagonalization of the secular equation. This program was written using Wolfram Mathematica, and holds several advantages over currently available software. These advantages include a graphical user-interface and parallelization capabilities
PH.D in Chemistry, July 2013
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Title: NON-INTRUSIVE LOAD MONITORING AND DEMAND RESPONSE FOR RESIDENTIAL ENERGY MANAGEMENT
Creator: Iwayemi, Abiodun
Date: 2016, 2016-05
Description: Compared to cellphone bills which itemize billing into local, international, text messaging, and data, todays electricity bills are opaque....
Show moreCompared to cellphone bills which itemize billing into local, international, text messaging, and data, todays electricity bills are opaque. Residential electricity customers receive a monthly bill detailing their aggregate energy usage, without any insight into which appliances are responsible for what proportions of their bill. We therefore created a Non-intrusive load monitoring framework that uses only data available from smart meters and the price signals from the Electric utility, and combine it with Optimal Stopping Rule-based schedulers to create a framework to equip residents with the information they need to be more energy efficient while balancing their costs and comfort. Non-intrusive load monitoring provides homeowners with detailed feedback on their electricity usage, but an open area is automated appliance labeling and the creation of generalizable appliance models that can be trained in one home, and deployed in another. Manually labeling such events to use them for disaggregating residential appliances is a costly and tedious task, and we developed two approaches for semisupervised learning of appliance signatures. The first approach uses 1-Nearest neighbor semi-supervised learning, and we developed a stopping criterion which reduces the likelihood of mislabeling appliance instances. This approach was extended to a cluster-then-label semi-supervised learning approach which can use only 3 labeled samples of each appliance to label and classify similar appliances within the home. Our approach enables the comparison of unequal length time series, and incorporates additional features extracted from the appliance time series. Finally, we develop a hybrid framework that combines detailed appliance models learned via Non-intrusive load monitoring with optimal stopping rule schedulers. We evaluated the performance of these models in terms of cost and delay, and explored the effect that errors in the real-time price and appliance models have on appliance running costs to demonstrate how our approach outperforms scheduling using only day head prices.
Ph.D. in Electrical Engineering, May 2016
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Title: MODELING STRATEGIC COMPETITION, TACTICAL DESIGN, AND OPERATIONAL PLANNING TO IMPROVE SUPPLY CHAIN PERFORMANCE
Creator: Li, Chia-hang
Date: 2017, 2017-05
Description: A supply chain is a network of facilities responsible for the production and delivery of goods and services from the initial raw materials to...
Show moreA supply chain is a network of facilities responsible for the production and delivery of goods and services from the initial raw materials to the end customers. Supply chain management, therefore, involves management of activities both within and among the organizations throughout the chain at every level of business management. In this dissertation, we address three specific supply chain problems at three distinct level of business management: (1) Operational capacity and production planning; (2) Tactical closed-loop channel structure design; and (3) Strategic platform competition. In each work, we identify strategies that lead the supply chain improvements.
Ph.D. in Management Science, May 2017
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Title: MOLECULAR MECHANISMS UNDERLYING SALMONELLA SURVIVAL ON SURFACE OF SELECTED NUTS AND FRUITS
Creator: Li, Ye
Date: 2017, 2017-07
Description: Salmonella enterica is the leading cause of bacterial foodborne illness in the United States. In recent years, S. enterica has been frequently...
Show moreSalmonella enterica is the leading cause of bacterial foodborne illness in the United States. In recent years, S. enterica has been frequently linked to foodborne outbreaks associated with nuts and fruits; however, the underlying mechanisms of such association have not been fully understood. In the first part of this study, we evaluated the impact of various environmental factors and food surface attributes on the attachment and survival of five S. enterica strains representing serotypes Typhimurium, Enteritidis, Montevideo, Mbandanka, and Braenderup on three different raw nuts (i.e. black peppers, almonds and hazelnuts) and two different S. enterica strains including serotypes Typhimurium and Enteritidis on two fresh fruits (i.e. grape tomatoes and cantaloupes) under storage conditions relevant to industrial practice. We observed significant inter-strain variations in S. enterica survival on nut and fruit surface. A direct correlation was found between the nut and fruit surface roughness and S. enterica attachment and survival. Lower relative humidity (20%) and higher storage temperature (25oC) resulted in significant S. enterica reduction on nut shells. Lower storage temperature at 4oC significantly reduced S. enterica population on grape tomatoes. In the second part of this study, we used a newly-developed transposon mutagenesis library in S. enterica serotype Enteritidis genome and highthroughput sequencing analysis to identify genes with potential roles in S. enterica attachment to and survival on almonds and grape tomatoes. A total of 336 and 210 S. enterica genes displayed significant selection on almonds and grape tomatoes over a 7-d storage period at 25oC (p<0.05), respectively. Our results suggest that various food attributes, environmental factors as well as bacterial determinants collectively contribute to the survival and persistence of S. enterica on nuts and fruits, providing new data for future development of knowledge-based intervention strategies.
Ph.D. in Biology, July 2017
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Title: HIGH-FREQUENCY TRADING, LOW-FREQUENCY TRADING AND THE LIMIT ORDER MARKET
Creator: Li, Kun
Date: 2015, 2015-07
Description: The emergence of High-Frequency Trading (HFT) has met with mixed reactions in both investment and academic communities. However, there still...
Show moreThe emergence of High-Frequency Trading (HFT) has met with mixed reactions in both investment and academic communities. However, there still exist gaps on distinguishing and interpreting the impact of HFT on the Low-Frequency Trading (LFT) side. In this thesis, I present three chapters that address the impact of HFT to LFT. I find evidence to distinguish trading generated by HFT in the limit order market, and consequently apply to explore how HFT affects LFT in terms of the liquidity and the order execution quality. In addition, I further explore the fleeting orders generated by HFT and their impact on the liquidity of LFT.
Ph.D. in Management Science, July 2015
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Title: DISTRIBUTED NOSQL STORAGE FOR EXTREME-SCALE SYSTEM SERVICES IN CLOUDS AND SUPERCOMPUTERS
Creator: Li, Tonglin
Date: 2015, 2015-12
Description: As supercomputers gain more parallelism at exponential rates, the storage infrastructure performance is increasing at a significantly lower...
Show moreAs supercomputers gain more parallelism at exponential rates, the storage infrastructure performance is increasing at a significantly lower rate due to relatively centralized management. This implies that the data management and data flow between the storage and compute resources is becoming the new bottleneck for large-scale applications. Similarly, cloud based distributed systems introduce other challenges stemming from the dynamic nature of cloud applications. This dissertation addresses several challenges on storage systems at extreme scales for supercomputers and clouds by designing and implementing a zero-hop distributed NoSQL storage system (ZHT), which has been tuned for the requirements of high-end computing systems. ZHT aims to be a building block for scalable distributed systems. The goals of ZHT are delivering high availability, good fault tolerance, light-weight design, persistence, dynamic joins and leaves, high throughput, and low latencies, at extreme scales (millions of nodes). We have evaluated ZHT’s performance under a variety of systems, ranging from a Linux cluster with 64-nodes, an Amazon EC2 virtual cluster up to 96-nodes, to an IBM Blue Gene/P supercomputer with 8K-nodes. This work also presents several real systems that have adopted ZHT as well as other NoSQL systems, namely ZHT/Q, FusionFS, IStore, MATRIX, Slurm++, Fabriq, FREIDAState, and WaggleDB, all of these real systems have been significantly simplified due to NoSQL storage systems, and have been shown to outperform other leading systems by orders of magnitude in some cases. Through our work, we have shown how NoSQL storage systems can help on both performance and scalability at large scales in such a variety of environments.
Ph.D. in Computer Science, December 2015
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Title: UNIDIRECTIONALLY ALIGNED COLLAGEN / COLLAGEN COMPOSITE FIBRILS AND THEIR MODULATION OF CELL BEHAVIORS
Creator: Li, Wen
Date: 2016, 2016-05
Description: One of the main goals of tissue engineering is to create new functional scaffolds with desired chemical and physical features mimicking the...
Show moreOne of the main goals of tissue engineering is to create new functional scaffolds with desired chemical and physical features mimicking the native micro-environment and modulating cell functions or behaviors. As collagen is abundant in the extracellular matrix (ECM) of native tissues, it is widely used to generate artificial scaffolds in in vitro. In this thesis research, aligned collagen and collagen-composite fibirls (COL-CNT and COLI-COLIII) were achieved via epitaxial growth of collagen on muscovite mica surface. It was found that hdpPSCs interacted with collagen fibrils by deforming the cell shape, harvesting the nearby collagen fibrils, and reorganizing the fibrils around the cell body to transform a 2D matrix to a localized 3D matrix. Such a unique 3D matrix prompted high expression of β-1 integrin around the cell body that mediates and facilitates the stem cell differentiation toward neural cells. By compositing collagen with carbon nanotube (CNT), aligned COL-CNT fibril was obtained with 3 times stiffer than pure collagen fibril and a 2 nm D-period increase. The anisotropic morphology and high stiffness of COL-CNT fibrils greatly facilitated the elongation of SKOV3 cells byregulating the cell-matrix adhesion, cytoskeleton arrangement and cell migration rate, finally promoted the epithelial-mesenchymal transition (EMT) of the SKOV3 cells. Aligned COLI-COLIII hybrid collagen fibrils exhibit higher stiffness than pure COLIII and stronger binding affinity than pure COLI. It is found that with the combined advantages of stiffness and binding affinity, aligned COLI-COLIII fibrils lead to fibroblast cytoskeleton elongation and enhanced cellular elasticity with stronger traction strain sulfured, which improves collagen synthesis ability of fibroblast with a higher collagen I percentage.
Ph.D. in Chemistry, May 2016
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Title: SECURE AND RESILIENT OPERATION OF CYBER-PHYSICAL POWER SYSTEMS
Creator: Li, Zhiyi
Date: 2017, 2017-07
Description: For economic reasons, modern power systems are commonly operated close to their secure limits so that they are vulnerable to unexpected severe...
Show moreFor economic reasons, modern power systems are commonly operated close to their secure limits so that they are vulnerable to unexpected severe disruptions such as disastrous cyberattacks and extreme weather events. This thesis is aimed at enhancing the security and resilience of power supplies for facilitating the development of a Smart Grid, when power systems in various parts of the world have been undergoing transitions toward cyber-physical systems. First, this thesis discusses common cybersecurity vulnerabilities in modern power systems and presents physical implications of cyberattacks on power system operations. In particular, this thesis analyzes a specifc type of coordinated cyberphysical attacks that could lead to undetectable line outages. Coordinated with physical attacks causing line outages, cyberattacks comprising topology preserving and load redistribution attacks could mask and potentially exasperate the outages to trigger cascading failures. Such coordinated cyber-physical attacks are analyzed in a bi-level optimization model which is then transformed into a mixed-integer linear programming problem. The proposed model and the two-stage solution algorithm are examined by case studies based on the IEEE 14-bus and 118-bus test systems. Second, this thesis offers the pertinent studies on quantifying the risk of cybersecurity vulnerabilities in power system operations. A type of locally coordinated cyber-physical attacks is analyzed in detail, which would cause undetectable line outages in local areas without the need for complete network information. A risk-based optimization model in the mixed-integer linear programming form is presented for analyzing physical implications resulting from the power ow redistribution. An efficient greedy search-based heuristic method is then developed to offer satisfactory solutions for real-time applications, which are verified by case studies based on a six-bus system and the two-area IEEE RTS-96 system. Third, this thesis studies security measures for mitigating the cybersecurity risk in power system operations. A game-theoretic framework is built for determining the optimal combination of security measures based on the minimax-regret decision rule. The resulting multi-level optimization model is reformulated as a bilevel mixed-integer linear programming problem. An implicit enumeration algorithm is then developed to achieve an exact solution to this complex problem. Acceleration techniques are also provided to improve the computation efficiency for large-scale power system applications. The proposed model and solution methods are validated by case studies based on a six-bus test system and the two-area RTS-96 system. Fourth, this thesis extends the discussion of cybersecurity vulnerabilities to the operation of distributed power systems like microgrids. Since microgrids are regarded as building blocks of a Smart Grid, they strive for cyber-secure operations for sustaining power services to local customers. The assessment and mitigation of the cybersecurity risk in microgrid operations is then presented in depth. Additional opportunities provided by software-defined networking technologies to enhance the microgrid cybersecurity are also realized by the proposed defense-in-depth framework that comprises three lines of defense against cyberattacks. Last, this thesis investigates the role of networked microgrids in enhancing the power system resilience against extreme events. Since resilience is an intrinsically complex property which requires deep understanding of power system operations, a generic simulation-based framework is developed for power system operators to analyze the resilience comprehensively and respond effectively in emergency conditions. The notion that the deployment of networked microgrids catalyzes the resilience enhancement in a Smart Grid is discussed in detail. Besides, the management of networked microgrids for achieving a higher degree of resilience, reliability, and efficiency of power supplies is discussed based on the proposed hierarchical control framework.
Ph.D. in Electrical Engineering, July 2017
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Title: MEASURING DEGREE OF BILINGUALISM AND ITS EFFECT ON COGNITIVE PERFORMANCE
Creator: Leon, Adeline
Date: 2017, 2017-07
Description: Bilingualism is a unique experience that has been shown to have a distinct impact on cognitive performance: disadvantages in language...
Show moreBilingualism is a unique experience that has been shown to have a distinct impact on cognitive performance: disadvantages in language production (Gollan, Montoya, Fennema-Notestine, & Morris, 2005) and advantages in executive functioning skills (Bialystok, Craik, Klein, Viswanathan, 2004; Costa, Hernandez, Sebastian-Galles, 2008). However, some researchers assert that bilingual differences do not exist at all (Kousaie & Phillips, 2012a, 2012b; Paap & Greenberg, 2013). These discrepancies can have a substantial effect on neuropsychological assessment results, diagnoses, and treatment recommendations. The purpose of this study was to measure bilingualism in patients presenting for neuropsychological testing to determine the effect of degree of bilingualism on cognitive performance. Bilingualism was measured in an objective, continuous manner using the Peabody Picture Vocabulary Test (PPVT; Dunn & Dunn, 2007) to assess proficiency in English and the Test de Vocabulario en Imagenes Peabody (TVIP; Dunn, Lugo, Padilla, Dunn, 1986) to assess proficiency in Spanish. This bilingualism index was used to measure the effect of degree of bilingualism on neuropsychological test performance in English/Spanish bilinguals assessed in their dominant language. Archival data from 99 participants presenting for neuropsychological testing were used to examine the bilingualism effect on the following cognitive domains: shifting of set, divided attention, naming, lexical retrieval, and verbal working memory. With the exception of the BNT, results of linear regression analyses revealed no significant effect of bilingualism on cognitive performance in any of the domains measured. Future research may investigate alternative ways to measure bilingualism to facilitate proper diagnosis and treatment recommendations in a clinical population.
Ph.D. in Psychology, July 2017
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Title: NOVEL SUPERCAPACITORS MADE OF ACTIVATED CARBON WITH MECHANICAL ACTIVATION OR THROUGH MICRO-EXTRUSION OF HIGH CONCENTRATION GRAPHENE SLURRIES
Creator: Li, Ling
Date: 2016, 2016-12
Description: The overarching objective of this project is to investigate a novel concept of three - dimensional (3D) supercapacitors (SCs) with 3D...
Show moreThe overarching objective of this project is to investigate a novel concept of three - dimensional (3D) supercapacitors (SCs) with 3D interpenetrating positive and negative electrodes. Such 3D SCs are expected to be able to convert the high energy and high power densities based on the active electrode materials into comparable high energy and high power densities for assembled SCs. The SCs will be fabricated via micro-extrusion method layer by layer. The electrode will be fabricated from graphene/activated carbon (AC)-based materials. We investigated two types of graphene, graphene slurries preparation and characterization in this study. Activated carbon (AC) was processed with different ball milling conditions. The characterization of graphene and activated carbon with different conditions were performed using SEM, BET, TGA, RAMAN, FTIR methods. Galvanostatically cycling and cyclic voltammetry tests were conducted on AC with different conditions. The ball milled 6-hour AC has specific capacitance high up to 102F/g (209μF/cm2) specific. High energy ball milling can induce oxidization of AC which makes the capacity of materials increases.
Ph.D. in Materials Science and Engineering, December 2016
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Title: VOLATILITY FORECASTING USING A DECISION-BASED ATTRIBUTION FRAMEWORK
Creator: Li, Tingting
Date: 2016, 2016-05
Description: This research develops a portfolio volatility forecasting method for absolute return equity strategies with consideration of managers’...
Show moreThis research develops a portfolio volatility forecasting method for absolute return equity strategies with consideration of managers’ investment skills. Besides the portfolio holdings and prices that are commonly used by existing volatility forecast methodologies, the method proposed in this research takes account of investment skills and their volatility attribution. Investment skills are indicated by decisions of constructing portfolio overtime. Portfolio volatility is attributed to investment decisions through use of decision-based performance attribution model. It is shown that tracking the information contained in the time series of investment decision attribution leads to better volatility forecasts than commonly used forecasting methods which directly use returns and holdings. The forecasting method proposed has advantage of explaining risk forecast in terms of actual investment decisions, and changes to those decisions in real time.
Ph.D. in Management Science, May 2016
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Title: COMPARISON OF NEUROPSYCHOLOCICAL PROFILES OF CHILDREN WITH ATTENTION.DEFIC ITiHYPERACTIVITY DISORDER (ADHD), READING DISORDER (RD), AND COMORBID ADHD AND RD
Creator: Hinkle, Clayton D.
Date: 2013, 2013-07
Description: The aim of this study was to expand our understanding of the patterns of executive functioning, memory and learning, and reading achievement...
Show moreThe aim of this study was to expand our understanding of the patterns of executive functioning, memory and learning, and reading achievement in older children and adolescents with ADHD, RD, and comorbid ADHD and RD. Each participant completed neuropsychological assessments, including a measure of intelligence and reading achievement, as well as several measures of executive functioning, memory, and learning. Results suggested that children in these diagnostic groups do significantly differ from each other on these tasks, although those with comorbid ADHD and RD did not demonstrate any specific deficits above and beyond those that manifest in either ADHD or RD alone. Clinical and practical implications, as well as directions for future research are discussed.
PH.D in Psychology, July 2013
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