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Title: Improving Localization Safety for Landmark-Based LiDAR Localization System
Creator: Chen, Yihe
Date: 2024
Description: Autonomous ground robots have gained traction in various commercial applications, with established safety protocols covering subsystem...
Show moreAutonomous ground robots have gained traction in various commercial applications, with established safety protocols covering subsystem reliability, control algorithm stability, path planning, and localization. This thesis specifically delves into the localizer, a critical component responsible for determining the vehicle’s state (e.g., position and orientation), assessing compliance with localization safety requirements, and proposing methods for enhancing localization safety.Within the robotics domain, diverse localizers are utilized, such as scan-matching techniques like normal distribution transformations (NDT), the iterative closest point (ICP) algorithm,probabilistic maps method, and semantic map-based localization.Notably, NDT stands out as a widely adopted standalone laser localization method, prevalent in autonomous driving software such as Autoware and Apollo platforms.In addition to the mentioned localizers, common state estimators include variants of Kalman Filter, particle filter-based, and factor graph-based estimators. The evaluation of localization performance typically involves quantifying the estimated state variance for these state estimators.While various localizer options exist, this study focuses on those utilizing extended Kalman filters and factor graph methods. Unlike methods like NDT and ICP algorithms, extended Kalman filters and factor graph based approaches guarantee bounding of estimated state uncertainty and have been extensively researched for integrity monitoring.Common variance analysis, employed for sensor readings and state estimators, has limitations, primarily focusing on non-faulted scenarios under nominal conditions. This approach proves impractical for real-world scenarios and falls short for safety-critical applications like autonomous vehicles (AVs).To overcome these limitations, this thesis utilizes a dedicated safety metric: integrity risk. Integrity risk assesses the reliability of a robot’s sensory readings and localization algorithm performance under both faulted and non-faulted conditions. With a proven track record in aviation, integrity risk has recently been applied to robotics applications, particularly for evaluating the safety of lidar localization.Despite the significance of improving localization integrity risk through laser landmark manipulation, this remains an under explored territory. Existing research on robot integrity risk primarily focuses on the vehicles themselves. To comprehensively understand the integrity risk of a lidar-based localization system, as addressed in this thesis, an exploration of lidar measurement faults’ modes is essential, a topic covered in this thesis.The primary contributions of this thesis include: A realistic error estimation method for state estimators in autonomous vehicles navigating using pole-shape lidar landmark maps, along with a compensatory method; A method for quantifying the risk associated with unmapped associations in urban environments, enhancing the realism of values provided by the integrity risk estimator; a novel approach to improve the localization integrity of autonomous vehicles equipped with lidar feature extractors in urban environments through minimal environmental modifications, mitigating the impact of unmapped association faults. Simulation results and experimental results are presented and discussed to illustrate the impact of each method, providing further insights into their contributions to localization safety.
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Title: Effect of organic acid treatment in reducing Salmonella on six types of sprout seeds
Creator: Yang, Dachuan
Date: 2023
Description: Fresh sprouts present a special food safety concern as their growing conditions also favor the growth of pathogens such as Salmonella....
Show moreFresh sprouts present a special food safety concern as their growing conditions also favor the growth of pathogens such as Salmonella. Contamination in sprouts often originates from the seeds used for sprouting. The Produce Safety Rule requires that seeds used to grow sprouts be treated to reduce pathogens. The treatments may be applied by sprout growers or by seed suppliers. Although 20,000 ppm calcium hypochlorite is the most used seed treatment method, the high chlorine level can be hazardous to workers and the environment. Alternative seed treatment methods that are safe and environmentally friendly are needed. In addition, a post-treatment drying step is needed when seed suppliers are using chemical seed treatment methods. This study evaluated the efficacy of an organic acid solution for reducing Salmonella on six types of seeds (alfalfa, clover, radish, mung bean, onion, and broccoli). The impact of treatment on seed germination and sprout yield was also examined. Ten grams of seeds inoculated with a five-serotype cocktail of Salmonella were pre-rinsed with 40 ml of water twice and treated with 75.7 ml of the organic acid solution for 1 hour. The treated seeds were either not rinsed or rinsed with 40 ml of water twice before being dried in the biological safety cabinet for 24 hours. The Salmonella level, germination percentage, and sprout yield of seeds treated with water, seeds treated with the organic acid solution, seeds treated with organic acid, dried, and rinsed, and seeds treated with organic acids, dried, and not rinsed were compared. Salmonella reductions that could be achieved with this organic acid solution treatment were less than 0.5 log CFU/g without drying, 0.6-2.0 log CFU/g with drying and rinse, or 1.6-2.9 log CFU/g with drying and no rinse. Drying significantly enhanced the treatment efficacy (p < 0.05 ) on alfalfa, radish, mung bean, and onion seeds. If seeds were not rinsed after treatment, the log reductions achieved on mung bean and onion seeds were significantly higher (p < 0.05). If seeds were treated and rinsed, the germination rates of six types of seeds were not affected (p > 0.05) regardless of whether the seeds were dried or not. All treatments significantly decreased the sprout yield of clover seeds by 13% (p < 0.05 ). If seeds were not rinsed after treatment, the germination rates of clover and broccoli seeds were reduced by 7 and 9%, respectively, and the sprout yield of alfalfa seeds was reduced by 35%. Overall, the organic acid solution was ineffective when compared with 20,000 ppm calcium hypochlorite in reducing Salmonella on sprout seeds, although the drying step after treatment could improve the treatment efficacy.
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Title: Utilizing Image Processing in Evaluation of Fibroblast Stimulation for Collagen Remodeling
Creator: Yoon, Shin Hae
Date: 2023
Description: This research delves into the realm of image processing as a pivotal component in the evaluation of fibroblast stimulation for collagen...
Show moreThis research delves into the realm of image processing as a pivotal component in the evaluation of fibroblast stimulation for collagen remodeling. The study focuses on unraveling the intricate synergy between electrospun silk fibroin-carbon nanotube (SF-CNT) fibers and electrical stimulation, working in harmony to enhance tissue regeneration. Building upon our previous work, we successfully engineered SF-CNT fibers through the electrospinning process, yielding highly aligned structures reminiscent of natural extracellular matrix proteins. These fibers were fortified with water stability through post-treatment with ethanol vapor, while subtle additions of carbon nanotubes (CNTs) significantly improved fiber alignment, strength, and conductivity without compromising biocompatibility. This innovative platform served as a cell culture matrix for fibroblasts harvested from pelvic organ prolapse (POP) patients, facilitating electrical stimulation that triggered a substantial increase in collagen production. In this study, we harnessed the power of various image-processing software tools, including ImageJ and Python, to analyze immunostained images of fibroblasts obtained from POP patients. Under carefully tailored electrical stimulation conditions, the stimulated cells exhibited an astonishing up to 11.97-fold increase in alpha-smooth muscle actin (α-SMA) expression, unequivocally signifying the successful activation of myofibroblasts. Additionally, in an animal model employing LOX-knockout mice to mimic collagen disorders associated with POP, the application of optimized electrical stimulation conditions for patient 003 led to a remarkable surge in collagen production and structural enhancement, underlining the potential of electrical stimulation in expediting tissue remodeling. Intriguingly, fibroblasts from patient 005 and patient 006 exhibited a distinct response, shedding light on the influence of POP severity on cellular behavior. This study firmly reinforces the imperative of personalized therapeutic approaches, emphasizing the need to customize treatment strategies to align with individual patient characteristics through innovative biological image analysis techniques.
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Title: Using Niobium surface encapsulation and Rhenium to enhance the coherence of superconducting devices
Creator: Crisa, Francesco
Date: 2024
Description: In recent decades, the scientific community has grappled with escalating complexity, necessitating a more advanced tool capable of tackling...
Show moreIn recent decades, the scientific community has grappled with escalating complexity, necessitating a more advanced tool capable of tackling increasingly intricate simulations beyond the capabilities of classical computers. This tool, known as a quantum computer, features processors composed of individual units termed qubits. While various methods exist for constructing qubits, superconducting circuits have emerged as a leading approach, owing to their parallels with semiconductor technology.In recent years, significant strides have been made in optimizing the geometry and design of qubits. However, the current bottleneck in the performance of superconducting qubits lies in the presence of defects and impurities within the materials used. Niobium, owing to its desirable properties, such as high critical temperature and low kinetic inductance, stands out as the most prevalent superconducting material. Nonetheless, it is encumbered by a relatively thick oxide layer (approximately 5 nm) exhibiting three distinct oxidation states: NbO, NbO$_2$, and Nb$_2$O$_5$. The primary challenge with niobium lies in the multitude of defects localized within the highly disordered Nb$_2$O$_5$ layer and at the interfaces between the different oxides. In this study, I present an encapsulation strategy aimed at restraining surface oxide growth by depositing a thin layer (5 to 10 nm) of another material in vacuum atop the Nb thin film. This approach exploits the superconducting proximity effect, and it was successfully employed in the development of Josephson junction devices on Nb during the 1980s.In the past two years, tantalum and titanium nitride have emerged as promising alternative materials, with breakthrough qubit publications showcasing coherence times five to ten times superior to those achieved in Nb. The focus will be on the fabrication and RF testing of Nb-based qubits with Ta and Au capping layers. With Ta capping, we have achieved the best T1 (not average) decay time of nearly 600 us, which is more than a factor of 10 improvements over the bare Nb. This establishes the unique capping layer approach as a significant new direction for the development of superconducting qubits.Concurrently with the exploration of materials for encapsulation strategies, identifying materials conducive to enhancing the performance of superconducting qubits is imperative. Ideal candidates should exhibit a thin, low-loss surface oxide and establish a clean interface with the substrate, thereby minimizing defects and potential sources of losses. Rhenium, characterized by an extremely thin surface oxide (less than 1 nm) and nearly perfect crystal structure alignment with commonly used substrates such as sapphire, emerges as a promising material platform poised to elevate the performance of superconducting qubits.
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Title: Measurement and Control of Beam Energy at the Fermilab 400 MeV Transfer Line
Creator: Mwaniki, Matilda W.
Date: 2023
Description: Linac is the first machine in the Accelerator chain at Fermilab where particles are accelerated from 35 keV to 400 MeV and travel to the...
Show moreLinac is the first machine in the Accelerator chain at Fermilab where particles are accelerated from 35 keV to 400 MeV and travel to the Booster where they are stripped of the extra electrons to become protons. Tuning Linac is performed using diagnostics to ensure stable intensity and energy while minimizing uncontrolled particle loss. I have been revisiting diagnostics in the Linac in order to understand their signals and to ensure their data is reliable. I revisited Beam Loss Monitors (BLMs) for the loss data confidence. For the confidence of energy data there were two approaches. The first approach was time-of-flight measurements using Beam Position Monitors (BPMs) and beam velocity stripline pick-up that provides beam phase data. The second approach used the relation between beam position data from BPMs and dispersion values from MAD-X simulation to calculate energy. Our goal after understanding the data from the Linac diagnostics and finding the data reliable is to control the Linac parameters using Machine Learning techniques to increase the reliability and quality of beam delivered from Linac.
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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: 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: 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: SELF-HEALING IN MICROGRID OPERATION AND MESSAGE-PASSING BASED DEMAND RESPONSE
Creator: Barati, Masoud
Date: 2013, 2013-12
Description: Electrical energy can be more efficiently and reliably generated, transmitted, and consumed over electricity grids as smart grids evolve....
Show moreElectrical energy can be more efficiently and reliably generated, transmitted, and consumed over electricity grids as smart grids evolve. Through the two-way flow of information between suppliers and consumers, the grids can encourage and adapt more easily to the increased consumer participation in energy management through demand response. This dissertation studies the transactive energy management on the residential side via microgrid operation and message-passing based demand response. A microgrid is an independent section of the electrical distribution grid with capabilities to transmit, produce, and distribute power within a localized area. The implementation of the microgrid increases the reliability and quality of power supply through various means including the self-healing paradigm. A microgrid operating under a self-healing paradigm can automatically and intelligently detect and reroute the power flow around an unexpected line fault. This dissertation presents the formulations and the methodologies of the self-healing process, which is incorporated into the microgrid operation for real-time scheduling. The self-healing process tries to find the best topology of the microgrid including radial and closed-loop configurations that minimize the total operation cost while respecting all security constraints. The dissertation also considers the AC solution of optimal power flow for self-healing applications, which enhances the reactive power flow for mitigating any bus voltage violations and for alleviating any real and reactive loop flows. The message-passing based demand response scheme relies on dynamic pricing of electricity to regulate electricity consumption. To achieve this goal, load serving entities via messages-passing gather the information such as consumers’ usage of electricity from xv ii smart meters, and set the dynamic price level appropriately in order to reduce the peak electricity demand through the cooperation of customers. In response to the dynamic price signals, customers can shift their demands automatically, with the help of a home energy management system, or manually to the off-peak hours so as to minimize their electricity payment and maximize its utility function. The message-passing based demand response scheme is applied in this dissertation to residential household scheduling, which is a key component of a future smart grid that can help reduce peak loads and adjust elastic demands to provide economic and emergency demand responses. A decentralized and iterative message-passing method is developed for solving the residential household scheduling problem. Under the context of a competitive retail electricity market, this dissertation analytically models load serving entities’ production function based on wellknown economic theory, analytically models household behaviors based on the ordinal and cardinal concepts of the utility function and using a static game strategy, and efficiently calculates retail electricity price with pure ex-ante or combinatorial pricing strategies. A simple yet effective price stabilization strategy for retail electricity price is proposed to mitigate the potential price and consumption spike caused by uncertainties in wholesale electricity prices.
PH.D in Electrical Engineering, July 2013
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Title: PANCREATIC ADENOCARCINOMA: SECRETORY MARKERS AND CORRELATION WITH PARKINSON’S DISEASE
Creator: Gayatri, Sitaram
Date: 2011-04-27, 2011-05
Description: Pancreatic adenocarcinoma (PDAC), the fourth highest cause of cancer related deaths in the United States, has the most aggressive presentation...
Show morePancreatic adenocarcinoma (PDAC), the fourth highest cause of cancer related deaths in the United States, has the most aggressive presentation resulting in a very short median survival time for the affected patients. Early detection of PDAC is confounded by lack of specific markers. Proteins of importance in neurodegenerative diseases like Parkinson’s disease (PD) are believed to be of etiological significance and correlated to or be the cause/effect of pancreatic disease. Expression of proteins like PD autosomal recessive, early onset 7 (PARK-7/DJ-1), α-Synuclein (SNCA) both of which are known to be pathognomonic to Parkinson’s disease was found altered in various stages of the disease. Purine Nucleoside Phosphorylase (NP) has been exploited to be a therapeutic target in cancers. The expression of all these three proteins was found to be variable with the stage and existence of metastatic lesions in PDAC tissues. The protein levels of NP were higher in PDAC sera compared to the benign samples. The serum NP levels of other cancers viz. lung, kidney, colon and breast were also not elevated. While the serum levels of NP and those of its downstream metabolites have the potential to differentiating PDAC from benign, the expression levels of SNCA and PARK-7/DJ-1 allude to a possible nuance in the etiology of PD and PDAC.
M.S. in Biology, May 2011
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Title: MODELING AND SIMULATION OF DIRECT CARBON FUEL CELL ANODE IN CONNECTION WITH ANALYSIS AND CHARACTERIZATION OF WETTED CARBON ROD IN MOLTEN CARBONATE
Creator: Peng, Feng
Date: 2013, 2013-07
Description: Not available
M.S. in Chemical Engineering, July 2013

Title: EXTENSIONAL RHEOLOGY OF POLYISOBUTYLENE MELTS USING A COUNTER-ROTATING CYLINDERS RHEOMETER
Creator: Sun, David
Date: 2011-12-05, 2011-12
Description: Extensional rheology plays an immense role in many polymer processing operations, such as blow molding and fiber spinning. Extensional flow is...
Show moreExtensional rheology plays an immense role in many polymer processing operations, such as blow molding and fiber spinning. Extensional flow is a type of deformation that stretches a material and is sensitive to a polymer’s molecular structure. Elongational experiments are important in establishing flow models and verifying constitutive equations. Reliable extensional measurements and understanding of extensional rheology are vital for both academia and industry because they build upon the foundation for future theories, models, and applications. This study aims to understand the characteristics of a uniaxial elongation measuring technique and the validity of the data obtained. It focuses on the experimental properties of the Sentmanat Extensional Rheometer (SER), a specific uniaxial elongation rheometer, and tests the rheology for different molecular weights of polyisobutylene (PIB) melts. Through use of oscillatory shear, storage and loss modulus data are obtained and used to establish linear viscoelastic behavior. Using the SER, polyisobutylene was deformed to generate extensional viscosity data for different sample sizes, which was compared to the linear viscoelastic curve to check for consistency. Visual data analysis was used to examine deviations from ideal deformation. The results from this study were consistent with deviations seen by other researchers using the SER, and established experimental parameters that can improve performance of the SER. Based on elongational viscosity data, it is concluded that elongational viscosity does have a dependence based on sample size. In addition, this paper also quantifies the onset of surface instabilities, a phenomenon commonly seen, but not specifically reported. By utilizing the SER and different optical techniques, the development of the surface instability is examined. Analysis of the images demonstrates an appearance of surface striations that are consistent with different experimental parameters. By accurately capturing surface instabilities, they are found to be closely associated with sample deformations and onset of sample failure. By comparing visual and scattering images, the hencky strain (εinstability) at which instability occurs is consistently seen around 0.6 to 1.0. It is concluded that these striations are independent of strain rate, molecular weight, sample size, and technique. The validation of extensional viscosity’s dependence on sample size and onset of instability has great significance for uniaxial extension measuring tools, polymer processing, and extensional polymer modeling and simulation.
M.S. in Chemical Engineering, December 2011
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Title: INVESTIGATION INTO USE OF GEARLESS PMSG-BASED WIND FARM FOR GRID SUPPORT
Creator: Cui, Yinan
Date: 2011-12-05, 2011-12
Description: Wind energy has become the world’s fastest growing energy source，as environmental concerns have focused attention on the generation of...
Show moreWind energy has become the world’s fastest growing energy source，as environmental concerns have focused attention on the generation of electricity from clean and renewable sources. New capacity from wind turbines has been growing fast since 2004. Installed capacity reached 196630 Megawatt in 2010 worldwide. 2011 will also see good growth. Reliability and quality of the electrical power supply is of great importance for all grids. A well designed wind-turbine power source can help balancing the unpredictable power changes caused by the Load-side of the grid (Due to the meteorological nature of long-lasting wind at the sea, the offshore wind turbines are more stable in their power production aspect). Alone more and more R&D efforts, PMSG-based direct drive wind turbine generator has become a trend in the industry, its full scale back-to-back converters can achieve fast response of power factor tuning, which directly offers an option of generating a certain amount of reactive supporting power in solving short-term voltage stability problem in the local grid and a desired quantity of active power for mitigating the frequency oscillation in the system. Topics in this thesis includes: (1) analysis of the wind turbine generator model equipped with full scale back-to-back converters and their control schemes are proposed; (2) the low voltage ride-through test of a wind farm with the modeled wind turbine generator integrated into a finite 3-bus system is provided for further short term voltage stability studies; (3) the comparison is rendered between an offshore wind farm with no support on reactive power and the one with automatically reactive power support on voltage drop response in an 8-bus system connected with HVAC submarine cable; (4) study on dynamic active power compensation from wind farm for improving the frequency stability when large disturbance introduced. Keywords: PMSG, full scale converters, reactive power, short term voltage stability, active power, dynamic compensation
M.S. in Electrical Engineering, December 2011
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Title: ACCESSIBLE, ALMOST AB INITIO MULTI-SCALE MODELING OF ENTANGLED POLYMERS VIA SLIP-LINKS
Creator: Andreev, Marat
Date: 2014, 2014-12
Description: It is widely accepted that dynamics of entangled polymers can be described by the tube model. Here we advocate for an alternative approach to...
Show moreIt is widely accepted that dynamics of entangled polymers can be described by the tube model. Here we advocate for an alternative approach to entanglement modeling known as slip-links. Recently, slip-links were shown to possess important advantages over tube models, namely they have strong connections to atomistic, multichain levels of description, agree with non-equilibrium thermodynamics, are applicable to any chain architecture and can be used in linear or non-linear rheology. We present a hierarchy of slip-link models that are connected to each other through successive coarse graining. Models in the hierarchy are consistent in their overlapping domains of applicability in order to allow a straightforward mapping of parameters. In particular, the most–detailed level of description has four parameters, three of which can be determined directly from atomistic simulations. On the other hand, the least–detailed member of the hierarchy is numerically accessible, and allows for non-equilibrium flow predictions of complex chain architectures. Using GPU implementation these predictions can be obtained in minutes of computational time on a single desktop equipped with a mainstream gaming GPU. The GPU code is available online for free download.
Ph.D. in Physics, December 2014
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Title: DEVELOPING ALGORITHMIC TRADING STRATEGIES AND EMPIRICAL ANALYSIS WITH HIGH FREQUENCY TRADING DATA
Creator: Lee, Jeonghoe
Date: 2015, 2015-07
Description: The PhD dissertation research topics aim at developing algorithmic trading strategies and demonstrating data analysis skills. To be a...
Show moreThe PhD dissertation research topics aim at developing algorithmic trading strategies and demonstrating data analysis skills. To be a quantitative analyst as well as an academic scholar in financial trading area, these two professional backgrounds are indispensable. In detail, chapter 1 shows multi-objective optimization and spontaneous optimization of design variables. For instance, while conventional trading systems explore a single objective function, multi-objective optimization allows us to manage the essential trade-off among profit, standard deviation and maximum-drop. In addition, design parameters such as trading volume, the amount of historical data, and trading gateways of technical indicators are continuously optimized in real time. In chapter 2, this chapter shows an algorithmic trading system with the concept of machine learning, and demonstrating its various applications. The main purpose of this research is to propose objective numerical development framework in algorithmic trading. Chapter 3 pursues understanding liquidity measures which are critical for algorithmic traders and investors. Various liquidity measures have been suggested and they have different sensitivities to the market. This research analyzes liquidity measures and clarifies the relation between market price return & realized volatility and liquidity measures. In sum, with these three chapters, this dissertation will demonstrate necessary research topics in algorithmic trading.
Ph.D. in Management Science, July 2015
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Title: STABILITY OF AQUEOUS FOAMS: FOAM FILM STRATIFICATION PHENOMENON AND THE EFFECTS OF DISPERSED VERSUS SOLUBILIZED OIL
Creator: Lee, Jongju
Date: 2016, 2016-05
Description: A foam is a system consisting of a concentrated dispersion of gas bubbles in a liquid. Foams are encountered in many industries such as food,...
Show moreA foam is a system consisting of a concentrated dispersion of gas bubbles in a liquid. Foams are encountered in many industries such as food, agriculture, chemicals, petroleum, and paper manufacturing. Aqueous foams are formed by using surfactants or nano-colloidal particles. Thin liquid films containing surfactant micelles or other nano-colloidal particles are considered to be the key structural elements of foams containing gas and liquid. We thus probed the effects of the micellar concentration and the film size (area) on the stability of a dry bulk foam by studying the stability of a single foam lamella containing micelles; this is so we can establish the importance of the micellar structuring phenomenon and the foam film size (area) affecting the bulk foam stability. The film stratification phenomenon (stepwise film thinning) was experimentally observed by the reflected light microinterferometry. The stepwise layer-by-layer decrease of film thickness is due to the appearance and growth of dark spot (of one layer less film thickness) in the film. We used the two-dimensional diffusion model to model the dynamics of dark spot expansion considering the apparent diffusion coefficient and the film size. Based on this model, we carried out a parametric study depicting the effects of film thickness (or the number of micellar layers) and film area on the rate of dark spot expansion. Many practical applications involving three-phase foams (aqueous foams containing oil) commonly employ surfactants at several times their critical micelle concentration (CMC). We investigated the influence of both the dispersed and solubilized oils, and the surfactant concentration (above CMC) on the stability of an aqueous foaming system. In foam stability, the relative importance of the dispersed oil versus oil solubilized within the micelles depends on the stability of the aqueous asymmetric (i.e., pseudoemulsion) film between the oil and the air-water interface and the second virial coefficient. Also, the micellar structuring phenomenon tests using the single foam lamella revealed that the multi-layering structure was well pronounced in the absence of the solubilized oil; as a consequence, the foam lamellae thinned slowly layer-by-layer and the oil solubilized in micelles weakened the micellar structure formation. The foam lamellae thinned faster, making the foam less stable.
Ph.D. in Chemical Engineering, May 2016
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Title: THE CHARACTERIZATION OF TWO THERMOPHILIC STRAINS CONCERNING BIO-DESULFURIZATION OF DIBENZOTHIOPHENE BY THE 4S PATHWAY
Creator: Li, Enze
Date: 2016, 2016-05
Description: A moderately thermophilic Mycobacterium strain (denoted Myco-U) was isolated in our lab as a contaminant during the cultivation of another...
Show moreA moderately thermophilic Mycobacterium strain (denoted Myco-U) was isolated in our lab as a contaminant during the cultivation of another thermophilic Paenibacillus strain, and has been proved to harbor the genes that encode the enzymes for dibenzothiophene (DBT) biodegradation via the 4S pathway; this makes it possible to efficiently remove organosulfur compounds (e.g. DBT and DBTO2) from the crude petroleum. Through directed evolution (continuous passage and selection with increasing temperature), the Myco-U strain has shown moderate capacity of metabolizing DBT to 2-hydroxybiphenyl (2-HBP) by the 4S pathway at a thermophilic temperature (~53 ℃). In the middle-to-late stages of the selections, a stubborn contaminant (denoted Bacillus X) arose and has remained difficult to get rid of from our medium and cultures ever since, leading to a persistent contamination and repetition of our experiments. The reason why Bacillus X is regarded as a contaminant is that it does not obtain sulfur by the expected means (e.g., DBT desulfurization), but utilizes the tiny amount of sulfate from the vitamin mix and 50 μg/ml yeast extract in our medium to grow. This is confirmed by the facts that Bacillus X does not yield any detectable 2-HBP, and a significant difference of growth has been detected between cultures with DBT as the sole sulfur source and the positive controls, which employs Na2SO4 as sulfur source. Through 16S rDNA amplification, cloning, and sequencing, Bacillus X was identified as a Bacillus species, and shows the highest homology (99 % identical) to a specific uncultured bacterium clone (NCBI #Accession: JN882111.1). The chromogenic mechanism and impacts of pH and carbonate upon the Gibbs assay, by which 2-HBP is quantified, were investigated. When DBT is absent or at undetectably low levels, cultures measured by the assay display a yellowish-to-brownish background after adding the Gibbs reagent (2,6-dichloroquinone-4-chloroimide). According to our results, the Gibbs reaction prefers alkaline conditions and pH 8.0 ranks the optimal (compared with pH 7.0, 7.5, 8.5 and 9.0) at which the maximum A610nm is detected.
M.S. in Biology, May 2016
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Title: CHANGES OF BACTERIAL SPECIES AND HEME PROTEIN LEVEL IN ACTIVATED SLUDGE COMMUNITIES ACCLIMATED TO LOW AERATION
Creator: Li, Hainan
Date: 2016, 2016-05
Description: Increasing oxygen utilization of activated sludge under low dissolved oxygen (DO) conditions can lead to energy savings in wastewater...
Show moreIncreasing oxygen utilization of activated sludge under low dissolved oxygen (DO) conditions can lead to energy savings in wastewater treatment systems. Adaptation of sludge communities to low oxygen conditions may be facilitated by increased expression of heme proteins. One way to assess heme protein expression in sludge is to analyze the species present in the sludge community during the adaptation process. In the work reported here, growth of a sludge culture adapted by Kunkel to low aeration for 48 weekly passages was continued for an additional 26 passages (182 days). The activated sludge was cultured in synthetic wastewater under low DO conditions. Temperature, dissolved oxygen, and specific oxygen uptake rates (SOUR) were measured at the end of each weekly passage. The community structures of passages 50, 53 and 65 were determined by 16S rDNA cloning techniques. The type of heme present was identified using the pyridine hemochromogen method. The SOUR values measured increased slightly in the first part of the experiment, when the culture DO was very low, but then decreased in the latter part of the experiment, when the culture DO increased. The community structure diversity in passage 50 in Kunkel’s study and passage 50 from this work are totally different in terms of species present, even though the two cultures were both derived from Kunkel’s passage 48 and were grown under conditions which were matched as closely as possible for two additional passages. This indicates that the community structure is highly sensitive to small changes in growth conditions. From the point of view of types of hemoglobin (Hb), the community became more diverse by passage 53, containing all three types of truncated Hb (trHbN, trHbO, and trHbP), possibly due to the need for NO scavenging and oxygen transfer enhancement. The proportion of cells that synthesize truncated Hb decreased slightly through passages 50 to 53 to 65. The percentage of cells that encode FlavoHbs decreased from 84 % to 50 % by passage 65. Overall there was an increase in Hb expression from passage 50 to passage 65. Heme b expression in the sludge culture was confirmed. Successful adaptation of the sludge culture to low DO conditions via enhancement of oxygen uptake was not obvious in this study. Yet the overall tendencies of SOUR and Hb expression suggest that it is possible to acquire a culture more efficient in oxygen uptake if a stable low aerobic environment can be maintained for an extended period.
M.S. in Biology, May 2016
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Title: TEMPORAL AND SPATIOTEMPORAL MODELS FOR SHORT-CRIME PREDICTION
Creator: Liu, Xiaomu
Date: 2017, 2017-07
Description: One of the most important aspects of predictive policing is identifying the likely time and place of crime occurrences so as to prevent future...
Show moreOne of the most important aspects of predictive policing is identifying the likely time and place of crime occurrences so as to prevent future crimes. The ability to make short-term predictions may be of particular importance for optimizing police resource allocation. The goal of this study is to investigate the temporal and spatiotemporal pattern of crime in the city of Chicago and to build corresponding predictive models. First, a temporal model for forecasting citywide violent crime time count is proposed. This model is composed of a long-term trend and short-term variations using data of time, weather and crime. The importance of model reproducibility is addressed in this study to produce low-complexity models. We introduce an approach that provides a way to extend the model selection criterion to both prediction accuracy and model reproducibility. The experimental results show that models produced by this approach outperform several simple time-series models. It is also found that these models typically include fewer variables; therefore, they are more interpretable, and may provide superior generalization error. Next we develop a framework that provides predictions for tomorrow’s violent crime counts at the level of a police district. The procedures include citywide daily violent crime count prediction, violent crime density estimation, and distributing citywide predictions to districts according to the estimated densities. In order to estimate the crime spatial densities, we use mesh modeling and demonstrate that a mesh model can be used as the structure for modeling the spatial variation of crime rate since it is well adapted to the inhomogeneous crime distribution. The experimental results show that our method provides more-accurate forecasts than those given by historical crime statistics. One aspect of studying spatial pattern of crimes is identifying geographical regions with similar crime characteristics. Specifically, we illustrate applying unsupervised clustering techniques to segment the city into sub-regions. We explore the use of Gaussian mixture models combined with a Markov random field for the purpose of regularization. We also propose a framework for the evaluation of clustering models without knowing the ground truth, which can present a more-complete picture for model selection in unsupervised clustering problems. Finally, we develop a spatiotemporal prediction method that predicts the locations where violent crimes or property crimes are most likely to occur tomorrow. Crime incidents are rasterized by a spatiotemporal grid. Other factors that affect the time and location preferences of criminal activities are also leveraged and represented by that grid. Each spatiotemporal grid cell is treated as an example for training and testing our models. We also explore whether pooling data from various sub-regions based on spatial clustering can improve model performance. The experimental results show that our models are more accurate than conventional hot-spot models. It is found that the effects of using different training samples are not consistent, which depends on target crime type.
Ph.D. in Electrical Engineering, July 2017
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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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