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Title: INTELLIGENT SOLID STATE CIRCUIT BREAKERS USING WIDE BANDGAP SEMICONDUCTORS
Creator: Zhou, Yuanfeng
Date: 2021
Description: Electricity, in its predominant form of alternating current (AC), is at the heart of modern civilization. However, direct current (DC)...
Show moreElectricity, in its predominant form of alternating current (AC), is at the heart of modern civilization. However, direct current (DC) electricity is re-emerging, offering higher transmission efficiency, better system stability, better match with modern electrical loads, and easier integration of renewable and storage resources than AC. DC power is gaining tractions in HVDC or MVDC grids, DC data centers, photovoltaic farms, EV charging infrastructures, shipboard, and aircraft power systems. However, DC fault protection remains a major challenge. Interruption of DC currents is extremely difficult due to the lack of current zero crossings which are naturally available in AC power systems. Conventional mechanical breakers only offer a very limited DC current interruption capability even after significant power derating. Hybrid circuit breakers (HCBs) offers a relatively low conduction loss but a response time too slow to protect many low-impedance DC grids. Solid state circuit breakers (SSCBs) can quickly interrupt a DC fault current within tens of microseconds but suffer from high conduction losses. Furthermore, it is generally difficult for an SSCB to distinguish between a short circuit fault and a normal inrush current condition during the start-up of a capacitive load.The purpose of this thesis is to develop a tri-mode, intelligent solid-state circuit breaker technology using wide bandgap semiconductors (especially Gallium Nitride transistors), referred to as iBreaker. The iBreaker design methodology includes the use of mΩ-resistance GaN and SiC devices, new circuit topology and control techniques beyond the commonly used ON/OFF switch configuration, and integration of intelligent functions without increasing component count. The iBreaker adopts a distinct pulse width modulation (PWM) current limiting (PWM-CL) state in addition to the conventional ON and OFF states to facilitate soft startup, fault authentication, and fault location functions. Key design elements, such as use of wide bandgap (particularly GaN) switches, tri-mode operation, combined digital and analog control, the bidirectional buck topology, variable PWM frequency control and universal hardware/software architecture, are discussed in detail. Multiple iBreaker prototypes, rated at 380 V/20 A and 1000 V/10 A, respectively, are built and tested to validate the proposed SSCB design concept. 99.95% transmission efficiency, passive cooling, and μs-scale response time are demonstrated experimentally.
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Title: Systematic Serendipity: A Study in Discovering Anomalous Astrophysics
Creator: Giles, Daniel K
Date: 2020
Description: In the present era of large scale surveys, big data presents new challenges to the discovery process for anomalous data. Advances in astronomy...
Show moreIn the present era of large scale surveys, big data presents new challenges to the discovery process for anomalous data. Advances in astronomy are often driven by serendipitous discoveries. Such data can be indicative of systematic errors, extreme (or rare) forms of known phenomena, or most interestingly, truly novel phenomena which exhibit as-of-yet unobserved behaviors. As survey astronomy continues to grow, the size and complexity of astronomical databases will increase, and the ability of astronomers to manually scour data and make such discoveries decreases. In this work, we introduce a machine learning-based method to identify anomalies in large datasets to facilitate such discoveries, and apply this method to long cadence light curves from NASA's Kepler Mission. Our method clusters data based on density, identifying anomalies as data that lie outside of dense regions in a derived feature space. First we present a proof-of-concept case study and we test our method on four quarters of the Kepler long cadence light curves. We use Kepler's most notorious anomaly, Boyajian's Star (KIC 8462852), as a rare `ground truth' for testing outlier identification to verify that objects of genuine scientific interest are included among the identified anomalies. Additionally, we report the full list of identified anomalies for these quarters, and present a sample subset of identified outliers that includes unusual phenomena, objects that are rare in the Kepler field, and data artifacts. By identifying <4% of each quarter as outlying data, under 6k individual targets for the dataset used, we demonstrate that this anomaly detection method can create a more targeted approach in searching for rare and novel phenomena.We further present an outlier scoring methodology to provide a framework of prioritization of the most potentially interesting anomalies. We have developed a data mining method based on k-Nearest Neighbor distance in feature space to efficiently identify the most anomalous light curves. We test variations of this method including using principal components of the feature space, removing select features, the effect of the choice of k, and scoring to subset samples. We evaluate the performance of our scoring on known object classes and find that our scoring consistently scores rare (<1000) object classes higher than common classes, meaning that rarer objects are successfully prioritized over common objects. The most common class, categorized as miscellaneous stars without any major variability, and rotational variables compose well over two-thirds of the KIC, yet are considerably underrepresented in the top outliers. We have applied scoring to all long cadence light curves of quarters 1 to 17 of Kepler's prime mission and present outlier scores for all 2.8 million light curves for the roughly 200k objects.
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Title: Defense-in-Depth for Cyber-Secure Network Architectures of Industrial Control Systems
Creator: Arnold, David James
Date: 2024
Description: Digitization and modernization efforts have yielded greater efficiency, safety, and cost-savings for Industrial Control Systems (ICS). To...
Show moreDigitization and modernization efforts have yielded greater efficiency, safety, and cost-savings for Industrial Control Systems (ICS). To achieve these gains, the Internet of Things (IoT) has become an integral component of network infrastructures. However, integrating embedded devices expands the network footprint and softens cyberattack resilience. Additionally, legacy devices and improper security configurations are weak points for ICS networks. As a result, ICSs are a valuable target for hackers searching for monetary gains or planning to cause destruction and chaos. Furthermore, recent attacks demonstrate a heightened understanding of ICS network configurations within hacking communities. A Defense-in-Depth strategy is the solution to these threats, applying multiple security layers to detect, interrupt, and prevent cyber threats before they cause damage. Our solution detects threats by deploying an Enhanced Data Historian for Detecting Cyberattacks. By introducing Machine Learning (ML), we enhance cyberattack detection by fusing network traffic and sensor data. Two computing models are examined: 1) a distributed computing model and 2) a localized computing model. The distributed computing model is powered by Apache Spark, introducing redundancy for detecting cyberattacks. In contrast, the localized computing model relies on a network traffic visualization methodology for efficiently detecting cyberattacks with a Convolutional Neural Network. These applications are effective in detecting cyberattacks with nearly 100% accuracy. Next, we prevent eavesdropping by applying Homomorphic Encryption for Secure Computing. HE cryptosystems are a unique family of public key algorithms that permit operations on encrypted data without revealing the underlying information. Through the Microsoft SEAL implementation of the CKKS algorithm, we explored the challenges of introducing Homomorphic Encryption to real-world applications. Despite these challenges, we implemented two ML models: 1) a Neural Network and 2) Principal Component Analysis. Finally, we hinder attackers by integrating a Cyberattack Lockdown Network with Secure Ultrasonic Communication. When a cyberattack is detected, communication for safety-critical elements is redirected through an ultrasonic communication channel, establishing physical network segmentation with compromised devices. We present proof-of-concept work in transmitting video via ultrasonic communication over an Aluminum Rectangular Bar. Within industrial environments, existing piping infrastructure presents an optimal solution for cost-effectively preventing eavesdropping. The effectiveness of these solutions is discussed within the scope of the nuclear industry.
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Title: DEFAULT RISK AND MOMENTUM PREMIUM
Creator: Zhang, Yi
Date: 2022
Description: Birge and Zhang (2018) reported that combining common factors models with functions of the default risk improves models' performance to...
Show moreBirge and Zhang (2018) reported that combining common factors models with functions of the default risk improves models' performance to explain stock returns. Default risk contains firm specific information and may help to explain momentum premium that compensates investors for the firm specific risk exposures. In this paper, we confirmed that the forward-looking measure of default risk, as proposed by Birge and Zhang (2018), seems to capture some pricing information in the momentum premium. This provides an alternative to explain the underlying risks associated with the momentum strategy.
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Title: ENVIRONMENTAL AND SOCIAL SUSTAINABILITY IMPLICATIONS OF DOWNTOWN HIGH-RISE VS. SUBURBAN LOW-RISE LIVING: A CHICAGO CASE STUDY
Creator: Du, Peng
Date: 2015, 2015-12
Description: This research is focused on quantitatively investigating and comparing the environmental and social sustainability of people’s lifestyles in...
Show moreThis research is focused on quantitatively investigating and comparing the environmental and social sustainability of people’s lifestyles in terms of embodied energy, operational energy use, and overall satisfaction with their quality of life in both downtown high-rise and suburban low-rise living using Chicago, IL and a surrounding suburban area of Oak Park, IL as a case study. Specifically, in both cases, the study seeks to evaluate factors such as the embodied energy of the materials that comprise buildings in each location; the predicted and actual monthly energy consumption of the homes; travel via all modes of transport including automobile, public transport, walking, and biking; and the embodied and operational energy of the infrastructure to support each mode of transportation. In addition, this research also engages with the individual building occupants, including single individuals, couples, and families, in a large subset of downtown and suburban Chicago households to directly evaluate perceptions of their life satisfaction and sense of community, which offers a unique direct comparison between dense high-rise and suburban low-rise living. The findings of the study show that downtown high-rise living in Chicago accounts for approximately 58% more life-cycle energy per person per year than Oak Park low-rise living, on average, contrary to some common beliefs (best estimates were ~260 and ~165GJ/person/year, respectively). Building operational energy was estimated to be the single largest contributor of the total life-cycle energy in both the downtown high-rise and suburban low-rise cases, followed by vehicle OE. The findings of the study also show that downtown high-rise residents were associated with higher life satisfaction than suburban low-rise residents when controlling for demographic differences in the research sample. Residence type was not found to be associated with sense of community when controlling for demographic differences, and the factor that was found to be significantly associated with sense of community was household size in the research sample. Also, accessibility and safety were found as the strongest predictors of overall residential environment for individuals.
Ph.D. in Architecture, December 2015
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Title: OBJECT DETECTION AND VISUAL TRACKING SYSTEM
Creator: Kumar Moosad, Aditya Uday
Date: 2013, 2013-12
Description: The aim of the project is to design visual object detection and target tracking system. Such a system has been extensively used in military...
Show moreThe aim of the project is to design visual object detection and target tracking system. Such a system has been extensively used in military applications, but these days they find use in the civilian domain too, such as fault detection, geological surveys, remote sensing and domestic policing. Object detection and target tracking systems find use in robots and unmanned vehicles. In order to navigate and perform various operations on its own, these vehicles need to have intelligence. Therefore, developing an algorithm that would enable the robotic device to act on its own and make necessary changes to its trajectory would be a major breakthrough. Many algorithms have been developed to achieve this objective but they usually run in a pre-defined environment. In this project it is assumed that the environment is unknown and the drone has only visual data obtained by its frontend camera. The algorithm for object detection is based on the concept of determining image contours and utilizing the principle of image moments. Contours help detect the object and moment of the object is used to determine its size and therefore, its distance from camera. The algorithm for tracking has been developed using the Shi Tomasi algorithm for corner point detection and the pyramidal Lucas- Kanade optical flow algorithm to determine the motion vectors of the corner points. This is followed by the calculation of the local scale variance of these points and then estimating the time to collision. With these results the robotic device would be in a position to change its direction or trajectory. Therefore this algorithm performs real-time image processing of visual data provided by the drone and gives some kind of visual intelligence to the drone.
M.S. in Electrical Engineering, December 2013
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Title: EFFECTS OF CHROMIUM COMPOUNDS ON INSULIN-MEDIATED GLUCOSE UPTAKE
Creator: Yang, Liu
Date: 2012-04-13, 2012-05
Description: Chromium supplementation has been highlighted by its biological function in improvement of glucose metabolism. As essential trace nutrition,...
Show moreChromium supplementation has been highlighted by its biological function in improvement of glucose metabolism. As essential trace nutrition, chromium complex has great therapeutic potential in the alleviation of metabolic disorders, especially type II diabetes. This study is aimed at investigating the effect of two newly synthesized chromium (III) complexes Cr2(μ-OH)2(C4O4)2(H2O)4·(H2O)2, Cr2(μ-OH)2(μ1,2- C4O4)2(C2H6SO)4·(H2O)2 in comparison with a commercial compound CrCl3·6H2O on glucose uptake, as well as toxicity. We found that with 100 nM insulin stimulus, Cr2(μ- OH)2(C4O4)2(H2O)4·(H2O)2 significantly increased cellular glucose uptake, while Cr2(μ- OH)2(μ1,2-C4O4)2(C2H6SO)4·(H2O)2 inhibited the insulin-stimulated glucose uptake. Morphology study indicated that a relatively low concentration of these three complexes had little toxicity to cells within 24 h, but a higher concentration would lead to cell death. Cell growth curve supported the notion that the chromium (III) compounds in this study had no obvious cellular toxicity. Therefore, these results suggest that the newly synthesized less toxic chromium has a great potential in improvement of glucose metabolism in response to insulin. This study may provide valuable information in the treatment or management of diabetes. Keywords: Chromium, Insulin, Glucose uptake, Glucose metabolism, diabetes, type II diabetes
M.S. in Biology, May 2012
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Title: EFFICIENCY OF PATENT CONTRACTS
Creator: Liang, Shao-huai
Date: 2014, 2014-05
Description: This thesis attempts to analyze the incentive compatible (IC) region for the royalty contract in an innovation context. It also describes the...
Show moreThis thesis attempts to analyze the incentive compatible (IC) region for the royalty contract in an innovation context. It also describes the contracts that induce the licensee and the patentee to obtain the maximum pro t when using this licensing contract. We analyze the IC region for cost-reducing innovations " and royalty ratios in two situations: the non-drastic innovation and the drastic innovation. We also nd when licensing occurs, there is an e ciency loss. However, the IC region can limit the e ciency loss. Then, we extend our results to a two-stage game in order to check whether the royalty contract is still a good contract for both the licensee and the patentee from a pro t perspective. In stage two, when the size of innovation is smaller than the size of innovation in stage one, royalty contracts are inferior to other contracts. However, when the size of innovation in stage two is greater than that in stage one, the royalty contract is an improvement over other contracts.
PH.D in Management Science, May 2014
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Title: MICRO-SCALE EHD CONDUCTION-DRIVEN PUMPING AND HEAT TRANSFER ENHANCEMENT IN SINGLE- AND TWO-PHASE SYSTEMS
Creator: Pearson, Matthew
Date: 2011-04-19, 2011-05
Description: Electrohydrodynamic (EHD) pumping methods rely on the interaction between electric fields and the flow fields of a dielectric fluid....
Show moreElectrohydrodynamic (EHD) pumping methods rely on the interaction between electric fields and the flow fields of a dielectric fluid. Conduction pumping is one EHD pumping mechanism, which offers many advantages over other EHD pumping methods (for example, a simple design, no degradation of the working fluid, and no need for a temperature gradient). Conduction pumping can be used in an adiabatic context to pump a working fluid or it can be applied to deliver substantial enhancement to single- and two-phase heat transfer processes. Experimental studies of conduction pumping to date have focused on macro-scale devices with applied voltages on the order of 10 kV. However, like many other EHD concepts, conduction pumping depends primarily on the intensity of the imposed electric field. Therefore, at the micro-scale, the reduced physical size can be accompanied by a reduction in the magnitude of the applied voltage to levels that are significantly more manageable. Furthermore, the simplicity of EHD conduction pumps, such as the lack of moving parts, high reliability, and physical compactness, make them an attractive method for pressure generation in micro-scale fluid and heat transfer devices. This experimental study examines the fundamental behavior and performance of EHD conduction pumping at the micro-scale. The pump is embedded in a rectangular, adiabatic micro-channel, and the single-phase flow and pressure generation of the pump are characterized. The EHD pumping of single- and two-phase flows in micro-channels in the presence of heat transfer is also studied and the corresponding enhancement to single- and two-phase heat transfer is quantified. In an additional study, micro-scale electrodes are embedded within a flat, heated surface to examine the ability of the conduction pump to provide electrically-enhanced wetting of the heated surface during pool boiling. A model based on hydrodynamic instability theory is generated to quantify the influence of the EHD conduction pumping on the pool boiling critical heat flux. Finally, this technology is incorporated into two unique, novel, heat transport devices akin to a heat pipe but in which the primary driving force for the liquid is conduction pumping, not capillarity.
Ph.D. in Mechanical and Aerospace Engineering, May 2011
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Title: OPTIMAL ROUTING ALGORITHMS IN ENERGY-HARVESTING WIRELESS SENSOR NETWORKS
Creator: Martinez, Gina
Date: 2014, 2014-12
Description: Harnessing energy from environmental sources such as solar and wind is an attractive solution to the critical energy limitation problem in...
Show moreHarnessing energy from environmental sources such as solar and wind is an attractive solution to the critical energy limitation problem in wireless sensor networks. Energy harvesting can potentially provide the network with perpetual and sustainable operation, or it can prolong network lifetime even for high consumption applications so as to justify the high cost of deployment. However, in order to efficiently utilize harvested energy, the energy source dynamics need to be incorporated into the network design. One way to do so is to make the network layer routing algorithm energy-harvest-aware. One common property of environmental energy sources is that they are generally only intermittently available. To address this, a storage unit such as a rechargeable battery can be introduced into the system. However, this is only a partial solution due to finite buffer storage capacities that cause harvested energy to be wasted when full. In this work, we aim to maximize the network lifetime by optimizing the energy availability and consumption alignment. To realize this objective, we first show that the minimization of energy wastage is a necessary condition to the maximization of available network energy. We then propose an on-demand routing algorithm that maximizes the total residual network energy by minimizing the energy consumption and wastage. Next, we illustrate the tradeoff between the two objectives of maximizing the total network energy and maximizing the minimum network energy in prolonging network lifetime. Then, we propose a linear-programming routing solution that maximizes a utility objective function based on this tradeoff. Although these routing approaches are shown to achieve high energy utilization, they are still based on deterministic harvest and consumption models. In the last part of this work, we propose a routing algorithm by applying the Semi-Markov Decision Process. Using this method, we are able to incorporate a comprehensive consideration of stochastic solar availability and traffic models, heterogeneous network properties such as non-uniform energy buffer capacities and consumption rates, and the optimization of an analytical formulation for network lifetime.
Ph.D. in Electrical and Computer Engineering, December 2014
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Title: COORDINATION OF STORAGE WITH RENEWABLE ENERGY RESOURCES IN POWER SYSTEMS
Creator: Khodayar, Mohammad Esmaeil
Date: 2012-07-16, 2012-07
Description: The ever-increasing penetration of variable wind energy in power systems affects the hourly dispatch of thermal power generation in...
Show moreThe ever-increasing penetration of variable wind energy in power systems affects the hourly dispatch of thermal power generation in electricity markets. The coordination of wind power generation units with pumped-storage hydro (PS) generation could relieve the variability of wind energy and increase its hourly dispatchability. In this dissertation, a coordination methodology for wind and pumped-storage hydro (PS) units in the dayahead operation planning of power systems is proposed. With coordination, the PS unit can offset intrahour wind energy imbalances (i.e., deviations from hourly schedules) and minimize wind energy curtailments. The wind-PS coordination based on the application of stochastic security-constrained unit commitment (Stochastic SCUC) is evaluated in which, the hourly bus- level coordinated scheduling of wind energy and PS is compared with the system-level coordinated operation strategies in the day-ahead scheduling of power systems. Volatility of wind generation can also reduce the profit in day-ahead market by imposing potential imbalance charges in a generating company (GENCO). The dayahead price-based scheduling strategy for the coordination of wind and storage units in a GENCO is proposed based on the stochastic price-based unit commitment (PBUC) which considers volatilities in day-ahead intra-hour market prices and wind power generation when scheduling wind and storage units. The increased utilization of Plugin Electric Vehicles (PEVs), which consume electricity rather than fossil fuel for driving, offers unique economic and environmental opportunities, and brings out new challenges to electric power system operation and planning. The proposed approach evaluates the effect of integrating a large number of electric vehicles (EVs) on power grid operation and control. The coordinated integration of aggregated PEV fleets and renewable energy sources (wind energy) in power systems is studied by stochastic security-constrained unit commitment (Stochastic SCUC) model, which minimizes the expected grid operation cost while considering the random behavior of the many PEVs. Finally, the role of high reliability distribution system (HRDS) in microgrid operations is evaluated. HRDS, which offers a higher operation reliability and fewer outages in microgrids, is applied to looped networks in distribution systems. The storage system would enhance the microgrid reliability while offering hourly ancillary services and demand response for reducing operation costs. The HRDS implemented at Illinois Institute of Technology (IIT) is used as a case study along with the local DER to increase the load point reliability and decrease the operation cost of the microgrid.
Ph.D. in Electrical Engineering, July 2012
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Title: A SYSTEMS APPROACH TO MINIMIZE PESTICIDE HAZARDS ASSOCIATED WITH FRESH VEGETABLES
Creator: Kalle, Niranjan
Date: 2011-07-27, 2011-07
Description: Pesticides are used in agriculture for eradicating pests and to increase the yield and productivity crops. These pesticides show much effect...
Show morePesticides are used in agriculture for eradicating pests and to increase the yield and productivity crops. These pesticides show much effect on health of humans. There are different types of pesticides such as Insecticides, Herbicides, Fungicides and Pyrethroids. While there is a benefit for the use of pesticides, there can be a negative impact to human health. Exposure to these pesticides from ingestion or oral intake is the most common route of pesticide exposure. Removal of these pesticides from fruits and vegetables would lower the exposure and risk to human health from these pesticides. The objective of this research is to study the effectiveness of various washing methods for the reduction of pesticide residues from fresh fruits and vegetables. Samples of cherry tomatoes were treated with pesticide formulation of 120ppm which is prepared by mixing 6 pesticides (Bifenthrin, Chlorothalonil, Cyhalothrin, Cypermethrin, Malathion and Permethrin). Treated tomatoes were washed with solutions (water, Sodium hypochloride (80ppm), Peroxy acetic acid(80ppm), and Tween20(0.1%)). Ultrasonicator is used as a tool for washing along with the washing solvents. The % reduction of pesticides was determined by extracting the sample through QuECHERS (AOAC 2007.01) method and analyzed by using GC-MS and LC-MS/MS. The analysis of pesticide residues extracted from tomato samples by GC-MS and LC-MS/MS showed a significant reduction in pesticides when washed with peroxy acetic acid compared to sodium hypochlorite and Tween20. Washing with ultrasonicator in combination with washing solvents showed 10% more reduction than washing alone with solutions.
M.S. in Food Safety and Technology, July 2011
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Title: FALL DETECTION USING WIRELESS BODY SENSOR NETWORK
Creator: Sarkar, Oishee
Date: 2015, 2015-05
Description: The aim of this project is to develop a stand-alone wearable body sensor network with the primary aim of fall detection of human bodies. This...
Show moreThe aim of this project is to develop a stand-alone wearable body sensor network with the primary aim of fall detection of human bodies. This network should be able to detect a fall remotely and in real time, and send an intimation along with the relevant medical details to an emergency contact and/or the nearest hospital. Several methods of fall detection have been discussed in this report and the advantages and disadvantages of them are analyzed. An optimal fall detecting mech- anism has been chosen to perform the function. Physical sensors have been used for detection of the fall, namely accelerometers and gyroscopes. Data has been collected from these sensor, and a central processing node has been utilized to process the incoming data to determine whether a fall has taken place as well as detecting the position and orientation of the body that the sensors are strapped on to. A Rasp- berry Pi processor acts as the central node. The threshold technique is employed to determine if the body has fallen over, and in what orientation it lands. The smart phone is used as a communication node and the result from the processor is obtained in a form that can be sent to the smart phone via bluetooth for further operation.
M.S. in Electrical Engineering, May 2015
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Title: EFFECTS OF ENGINEERING USING BACTERIAL HEMOGLOBIN ON THE ABILITY OF ETHANOLOGENIC E. COLI TO FERMENT LIGNOCELLULOSIC HYRDOLYSATE TO ETHANOL
Creator: Kunkel, Stephanie
Date: 2011-05-03, 2011-05
Description: E. coli strain FBR5, which has been engineered to direct fermentation of sugars to ethanol has been further engineered in our laboratory using...
Show moreE. coli strain FBR5, which has been engineered to direct fermentation of sugars to ethanol has been further engineered in our laboratory using three different constructs, to contain and express the Vitreoscilla hemoglobin gene (vgb). The resulting strain (TS3) expresses VHb at a moderate level under microaerobic conditions in shake flasks and produces more ethanol than the parental strain (FBR5) with glucose, xylose, or corn stover hydrolysate as the carbon source. In the work reported here, this research was extended, focusing particularly on fermentation of lignocellulosic hydrolysate. The increased ability of the VHb-bearing strain to produce ethanol from pure glucose or xylose was confirmed. A VHb-correlated increase in ethanol production was also noted for lignocellulosic hydrolysate produced in our laboratory, but not for ligncellulosic hydrolysate prepared by the National Laboratory for Renewable Energy (NREL). Experiments were performed at several hydrolysate levels for both prepartories, in an attempt to determine the cause of the difference. One possibility is differences in levels of toxic hydrolysis byproducts in the two preparations as well as increased sensitivity to these toxins due to VHb expression.
M.S. in Biology, May 2011
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Title: PHOTOCATHODE TUNABILITY: THE PHOTOEMISSIVE PROPERTIES OF ULTRA-THIN MULTILAYERED MgO/Ag/MgO FILMS SYNTHESIZED BY PULSED LASER DEPOSITION
Creator: Velazquez, Daniel Gomez
Date: 2015, 2015-05
Description: Much of the early development of photocathode materials was aimed at the growth of photoemissive thin films with low work function, and high...
Show moreMuch of the early development of photocathode materials was aimed at the growth of photoemissive thin films with low work function, and high quantum efficiency (QE). It has been shown, both theoretically and experimentally, that metal-insulator junctions can lead to the modification of the work function and QE for coverages of a few monolayers of metal oxides on metallic substrates. However, the production of electron beams suitable for new photoinjector technologies in many instances requires low emittance beams from the cathode itself. Often the cathode intrinsic emittance plays an important role in new e-gun designs. A demonstration of the ability to control photoemissive properties by engineering the band structure of a photocathode could provide a pathway to meet the demands of new photoinjector technologies. Nemeth et al. [Phys. Rev. Lett. 104, 046801 (2010)] used density functional theory (DFT) to model the properties of a multilayered structure of MgO/Ag(001)/MgO with 4 monolayers of Ag(001) flanked by n monolayers (ML) of MgO. Their model indicated that it is possible to reduce the emittance of a photoemitted electron beam when the thickness n of the MgO layers is 2 or 3 monolayers because the surface band structure exhibits a narrowing of the density of occupied states in momentum near the Γ-point neighboring the Fermi Level. The theoretical prediction concerning the emission properties of these multilayers structures was tested by fabricating them, and then characterizing their emission properties. Synthesis of multilayered MgO/Ag/MgO films was performed using a custom-built pulsed laser deposition (PLD) system. In-situ growth monitoring was carried out by Reflection High-Energy Electron Diffraction (RHEED). Ex-situ techniques such as Scanning Tunneling Microscopy (STM), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (EDS) and Photoelectron Spectroscopy (PES) were used to show the formation of the crystalline and chemical structure of the multilayered films. A Kelvin Probe/photocurrent-detector system, custom-built for this research, was used to measure the work function and QE of the samples. Angle Resolved Photoelectron Spectroscopy was used to measure the angular photoelectron yield. Simultaneous reduction of work function and increase of QE was observed for (001) oriented multilayers of various thicknesses with respect to that of a bare Ag/MgO(001) surface. Work function measurements of multilayers of various thicknesses in the (111) orientation also registered a monotonic reduction with respect to that of a bare Ag/Si(111) surface. Angular emission was compared for a MgO/Ag/MgO multilayer (thicknesses of 3 ML/4 ML/3 ML) sample and Ag/MgO(001). Emission analysis of the angle-resolved photoelectron spectra shows a net change in the angular emission with high kinetic energy electron density shifted toward surface-normal emission. Experimental results were consistent with theoretical predictions, which open the promising possibility of customizing emission properties by direct manipulation of the surface band structure of the emitter.
Ph.D. in Physics, May 2015
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Title: INVESTIGATING MINDFULNESS AS A MODERATOR OF THE CONGRUENCE BETWEEN EXPLICIT AND IMPLICIT ATTITUDES OF HETEROSEXUAL MEN REGARDING HETEROSEXUALITY, HOMOSEXUALITY, AND BISEXUALITY
Creator: Unis, Barry J.
Date: 2014, 2014-12
Description: Althou gh some researchers have used implicit measures to investigate sexual orientation attitudes, very few have used the Implicit Relational...
Show moreAlthou gh some researchers have used implicit measures to investigate sexual orientation attitudes, very few have used the Implicit Relational Assessment Procedure (IRAP) , which has been shown to be very difficult for participants to provide fake results . This study investigated self-identified heterosexual male college students' explicit and implicit attitudes regarding the acceptability of heterosexual, homosexual, and bisexual people. Explicit measures includ ed the Modem Homonegativity Scale, Attitudes Regardin g Bisexuality Scale, Homonegati vity Scale, and the Collective Self-Esteem Scale. The impli cit measure was the IRAP. A one-way analysis of variance (ANOVA) revealed no statistically significant differences among explicit attitud es or implicit attitudes. Acceptability rankings based on the explicit measures were, from most to least, hetero sexual person, bisexual woman, bisexual man, lesbian, and gay man. In contrast, acceptability rankings based on the IRAP were heterosexual man, heterosexu al woman, gay man, bisexual man, bisexual woman, and lesbian. Mindfulness, measured using the Five-Facet Mindfulness Questionnaire, was investigated as a moderator between explicit and implicit attitudes. The moderation analysis was not statistically significant; however, mindfulness was related to attitudes toward bisexual people. Specifically, describin g thoughts and feelings was negati vely associated with negati ve attitudes toward bisexual people. This study adds to the literature by expanding the young research areas of bisexuality, implicit attitude s, and mindfulness, specifically the relationship between describing and attitudes toward bisexual people.
M.S. in Psychology, December 2014
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Title: SOCIAL SKILLS AND ACADEMIC ACHIEVEMENT: DIFFERENCES BETWEEN AFRICAN AMERICAN, CAUCASIAN, AND LATINO STUDENTS
Creator: Filerman, Stacey
Date: 2011-08, 2011-07
Description: Previous studies have demonstrated a significant relationship between social skills and academic achievement (McClelland, Morrison, & Holmes,...
Show morePrevious studies have demonstrated a significant relationship between social skills and academic achievement (McClelland, Morrison, & Holmes, 2000; Payton et al., 2008; Wentzel 1993). This relationship may be due to Vygotsky‟s and Bandura‟s social learning theories, in which learning occurs through observation, imitation, and interaction with one‟s environment (Bandura, 1997; Vygotsky, 1978). Large differences in academic achievement among minority and non-minority students in the United States have been documented for over three decades (Coleman, 1968; National Center, 1978- 1998). Current research examining differences in social skills and academic achievement by race/ethnicity is limited in that dichotomous comparisons have been made between Caucasian and African American, or minority students (Malecki & Elliot, 2002). Social skills measures have also been questioned for their construct validity among minorities (Van Horn, Atkins-Burnett, Karlin, Landesman Ramey, & Snyder, 2007). The current study attempts to expand the understanding of the relationship between social skills and academic achievement in African American, Caucasian, and Latino third, fourth, and fifth grade students. In particular, this study examined teacherand self-rated social skills, reading and mathematics achievement, English proficiency, an estimate of intelligence, and socio-economic status. The results of the current study revealed significant differences in teacher-rated social skills by Race/Ethnicity and no differences in self-ratings. Significant group differences were found also found in reading and not math. Regression analyses revealed teacher-rated social skills did not mediate the relationship between race/ethnicity and academic achievement.
Ph.D. in Psychology, July 2011
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Title: EXAMINING GROUP DIFFERENCES IN EXECUTIVE FUNCTIONS IN CHILDREN WITH MTBI AND ADHD
Creator: Bodzy, Mary Elizabeth
Date: 2011-05, 2011-07
Description: Executive Functions (EF) are described as behaviors associated with the frontal cortex of the brain that are responsible for higher order...
Show moreExecutive Functions (EF) are described as behaviors associated with the frontal cortex of the brain that are responsible for higher order thinking (Kolb & Whishaw, 1996), and aid in goal directed behavior (Gioia, Isquith, & Guy, 2001). Traumatic brain injury (TBI) and Attention Deficit Hyperactivity Disorder (ADHD) are two conditions that render the frontal systems vulnerable to dysfunction (Fletcher, et al., 1990; Singer & Walkup, 1991). Previous literature found EF deficits in children with ADHD (Barkley, 1997; Barkley, Edwards et al., 2007; Brocki, & Bohlin, 2006; Nigg et al., 2002; Solanto et al., 2001), and children with a TBI (Anderson et al., 2005; Catroppa, & Anderson, 2005; Catroppa et al., 2007; Mangeot et al., 2002; Nolin, 2006; Dennis et al., 1996; Ponsford et al., 1999; Yeates et al., 1999). The current study sought to examine the relationship between a performancebased measure and parent-report measure of EF domains, including working memory, inhibition/impulse control, attention, and processing speed. This study also explored group differences in EF domains between children with ADHD and mild TBI (mTBI), compared to controls in a sample of 180 participants 5-18 years old. Measures included a performance-based measure of EF (ImPACT) and parent-rated measure of executive functioning (BRIEF). Results indicated that parent-report and performance-based measures of executive functioning are related on some tasks (inhibition, emotional control, and monitoring were related to visual and working memory, and processing speed) and unrelated on others (organization, planning, and shifting unrelated to visual and working memory, processing speed, and impulse control). Females performed better than males on performance-based viii inhibition and working memory tasks and on parent-reported monitoring of behavior. After controlling for gender, effects for age, group, and age x group interaction were found on performance-based and parent-report of EF functioning. Specifically, effects for age (5-8, 9-12. 13-18) indicated differences between children of different ages on performance-based working memory and processing speed, and parent-reported working memory, inhibition, emotional control, and monitoring. Effects for group indicated differences between groups (ADHD, mTBI, controls) on performance-based working memory, and impulse control/inhibition, and parent-reported working memory, inhibition, initiation, planning/organization, organization of materials, and monitoring. The effect of the age x group interaction indicated differences on performance-based impulse control/inhibition and processing speed, and parent-reported working memory. In summary, the results of this study suggest there are developmental differences in executive functioning domains.
Ph.D. in Clinical Psychology, July 2011
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Title: NEW BEAMFORMING AND SPACE-TIME CODING SCHEMES FOR MIMO WIRELESS SYSTEMS
Creator: Tavassoli, Farhad
Date: 2013, 2013-05
Description: Space-time coding and Beamforming are two main techniques utilized in multiple-input multiple-output (MIMO) wireless systems to increase...
Show moreSpace-time coding and Beamforming are two main techniques utilized in multiple-input multiple-output (MIMO) wireless systems to increase channel capacity. In this work, we present new beamforming algorithms and space-time codes for MIMO wireless systems to reduce the complexity and enhance the performance. We present a new framework to obtain beamforming algorithms for code division multiple access (CDMA) and orthogonal frequency division multiplexing (OFDM) systems based on principal component analysis (PCA) approach. Four different PCA objective functions are used as examples to illustrate how to obtain new beamforming algorithms based on the proposed framework. Since two of the objective functions result in the same algorithm, three different beamforming algorithms are obtained for CDMA and OFDM systems. We show that the new algorithms offer a desirable performance while they have considerably lower computational complexity than the optimum algorithms. It is demonstrated that the proposed algorithms also have a fast convergence rate. We also propose new space-time codes for both coherent and non-coherent wireless systems which can provide lower symbol error rates than existing codes in the same class. For the coherent case, we propose a new quasi-orthogonal code to provide a full-rate full-diversity transmission. Unlike the other codes in the literature, the proposed code does not require the transmitted symbols to be chosen from two different constellations. Choosing all symbols from only one constellation reduces the required storage memory to half of that needed in other methods. It also avoids decreasing the minimum distance between the symbols and hence, avoids degrading the coding gain. For the non-coherent case, a new constellation design for differential unitary space-time modulation is proposed. We generate xi a set of unitary matrices from the multiplication of a simple unitary matrix with entries of 1 by diagonal matrices made from quaternary alphabets. Then, the proposed constellation is formed from the product of the optimum matrix chosen from this set and the optimized diagonal matrix first used for the cyclic codes. We show that the proposed constellation yields a larger diversity product as well as a lower union bound for pairwise error probability with the same or lower complexity compared to other existing constellations.
PH.D in Electrical Engineering, May 2013
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Title: ESSAYS ON DISTRIBUTIONALLY ROBUST PORTFOLIO OPTIMIZATION
Creator: Ousawat, Thitapon
Date: 2013, 2013-07
Description: Interest in distributionally robust optimization has been increasing recently. In this dissertation, we review recent developments in the...
Show moreInterest in distributionally robust optimization has been increasing recently. In this dissertation, we review recent developments in the literature in this eld and propose a model for distributionally robust mean-risk portfolio optimization. The model optimizes a risk-averse objective function with the worst-case return as reward and worse-case conditional Value-at-Risk as the risk measure. The model considers ambiguity in the distribution of data used to estimate the asset returns in the optimization model by creating an ambiguity set using -divergence measures which measure the distance between vectors. A numerical example is shown using the Kullback-Leibler divergence measure as the -divergence measure. A model for distributionally robust portfolio optimization with transaction costs is used to compare the performance of a distributionally robust mean-CVaR portfolio with the nominal as well as equally-weighted portfolio. The result shows that, under certain conditions, the distributionally robust model performs better than both the nominal and equally-weighted portfolio.
PH.D in Management Science, July 2013
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