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Title: ASSESSMENT OF STRUCTURAL INTEGRITY AND SEISMIC RETROFIT OF MASONRY BRIDGES USING MICROPILES
Creator: Caklr, Ferit
Date: 2011-07, 2011-07
Description: Masonry arch bridges are regarded as the oldest examples of engineered structures in the world; and they reflect the previous civilizations in...
Show moreMasonry arch bridges are regarded as the oldest examples of engineered structures in the world; and they reflect the previous civilizations in the world with their various sizes, styles, and spans. The preservation of these structures is receiving a great deal of attention in the structural engineering community. And as such, restoration, strengthening and reinforcement of historical masonry bridges have become a challenge for civil engineers. At the present time, most important problems of masonry arch bridges are heavy traffic loads and destructive natural disasters. These bridges were constructed centuries ago and they addressed the load-carrying problems of old times. With the passing of the time, the traffic changed and many natural disasters occurred. Correspondingly, loads on masonry arch bridges have increased and the traffic on the bridges have become more intense in the course of time. However, the bridges keep up to their initial performance; and this shows the complexity of their structural behaviors. This study provides the background information about masonry arch bridges and their components. It also helps us better understand the construction materials, structural properties and structural behavior of masonry arch bridges. In light of this background information, this study presents an overview of seismic retrofit for masonry arch bridges and a comprehensive study on the type, mechanism of failure and structural integrity of masonry arch bridges.
M.S. in Civil Engineering, July 2011
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Title: CLONING AND CHARACTERIZATION OF EXON EDITED HOTSPOT 1 ROD REGION DYSTROPHIN PROTEINS
Creator: Mahajan, Aayushi
Date: 2013, 2013-12
Description: Duchenne Muscular Dystrophy, DMD, one of the most common fatal genetic diseases, is caused by the absence of dystrophin protein. This protein...
Show moreDuchenne Muscular Dystrophy, DMD, one of the most common fatal genetic diseases, is caused by the absence of dystrophin protein. This protein is coded by the largest gene in the human genome, which has 79 exons and spans 2.4 Mbp. DMD affects 1 in 3600 boys and the average life expectancy of patients is 25 years. The most common type of defects leading to DMD are large exonic deletions that juxtapose remaining exons of incompatible phases, causing a frameshift. Inevitably this introduces a nonsense mutation (i.e. a stop codon) in the frame shifted exons and thus protein truncation. A related but milder condition called Becker’s Muscular Dystrophy, BMD, results when deletions are in-frame and so allow for the production of some, albeit modified, dystrophin protein. While there is no treatment available for DMD the recent clinical trials involving exon skipping suggest this will be highly promising treatment option. Exon skipping therapy is a strategy that uses anti-sense oligonucleotide analogs, AONs, to induce skipping of additional exons during mRNA maturation and thus restore the reading frame. This allows dystrophin translation to continue to its normal C-terminus, albeit with an internal deletion edit corresponding to both the original deletion, and newly skipped exon, which results in expression of protein thus converting the severe form of DMD to a milder form BMD. Frameshift causing deletions require exons that begin and end in different phases, and DMD deletions thus are clustered where such exons are located in, two so called ‘hotspots’ in the gene. The first of these occur in the region from exon 11-22 and is known as Hotspot 1. In many cases, DMD defects that are amenable to exon skip repair can be repaired in two or more alternative fashions by skipping of alternative exons. It is thought that the differences in severity of BMD, can range from being nearly as debilitating as DMD, to xi nearly benign, are at least in part related to the nature of the defect and its impact on the protein’s structure. Thus we are producing 5 different exon edited proteins from hotspot 1 rod region and assessing them for structure and stability as compared to unskipped fully functional dystrophin, to determine which edits hold the most promise of producing a well formed and stable edit.
M.S. in Biology, December 2013
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Title: MECHANISMS OF FOAMING, EFFECTS, PREVENTION, AND CONTROL IN ANAEROBIC DIGESTION
Creator: Subramanian, Bhargavi
Date: 2015, 2015-05
Description: Anaerobic digestion (AD) is an essential step to generate energy in the form of biogas from waste. Foaming during AD (AD foaming) is...
Show moreAnaerobic digestion (AD) is an essential step to generate energy in the form of biogas from waste. Foaming during AD (AD foaming) is widespread phenomenon and leads to deterioration of the AD process and operation. In extreme conditions, AD foaming poses a significant safety risk and considerable economic impacts. It is, therefore, necessary to understand the fundamentals of AD foaming to develop effective strategies that can help minimize and prevent the foaming impacts. Several aspects of AD foaming have attracted considerable research attention, however, the focus has been mainly on site specific causes and prevention. The work leading to this thesis was aimed to provide a better understanding of the AD foaming problem, to identify the underlying mechanisms, causes and contributors of foaming and to come up with foam management strategies for full-scale plants. Full-scale cylindrical digester investigations did not identify non-biological factors such as organic loading rate (OLR), mixing, and primary to waste activated sludge (PS:WAS) solids ratio as primary causes of foaming, but foam-causing filaments such as G. amarae and M. parvicella were determined to be primary causes. No foaming was observed over the duration of the study, indicating absence of a primary foaming cause even though the suspected contributors to AD foaming were present. In the case of full-scale egg-shaped digesters (ESD), foaming and foam collapse events were observed over the duration of the study over both during filamentous foaming and non-foaming seasons, indicating that the primary foaming cause requires the contributors to be present. The results of this study demonstrate that ESDs foamed due to high mixing and G. amarae counts above the threshold level (log #6 intersections/mg VSS) in mixed liquor. In both types of digesters, total solids and temperature profiles showed that reducing mixing frequency did not significantly impact digester performance or the homogeneity of the digester contents. Hence, mixing intensity optimization could be an effective strategy in addition to primary cause reduction of foam causing filaments.
Ph.D. in Environmental Engineering, May 2015
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Title: DESIGN AND ANALYSIS OF DATAPATH CIRCUITS USING MULTI-GATE TRANSISTORS
Creator: Garcia Martin, Martin
Date: 2015, 2015-07
Description: Multi-Gate Field-E ect Transistors are transistors with more than one gate that allows continuation of Moore's Law and performance increases...
Show moreMulti-Gate Field-E ect Transistors are transistors with more than one gate that allows continuation of Moore's Law and performance increases for CMOS tran- sistors. Introduction of multi-gate devices has been a turning point for the semi- conductor industry in facilitating transition from planar to 3D structures. Intel rst introduced commercial products using 3D structures (called Tri-Gate transistors) in late 2011 with Ivy Bridge CPUs using 22nm processes. Signi cant performance gains have been reported; i.e., 37% performance increase at low voltage and 50% power reduction. Multi-gate transistors based on 3D structures can vary greatly in their con guration and architectures leading to ambiguity in their design. It is necessary to investigate the performance of datapath circuits when multi-gate and independent- gate devices replace the conventional planar transistors. Therefore, key objective of this work has been to analyze these transistors' performance and to design new dat- apath circuits to leverage the inherent qualities of multi-gate transistor structures. Multiple-gate devices can be modeled using the BSIM-CMG (Common Multi- Gate) and BSIM-IMG (Independent Multi-Gate) compact models from University of Berkeley Device Group. In this research, both device types have been characterized for a variety of parameters to study their basic properties, functionality and to build a foundation for improved circuit designs. In particular, BSIM-CMG devices have been compared with CMOS planar technology demonstrating signi cant advantages in all design metrics, meanwhile the BSIM-IMG have been used to design new gates and improve datapath designs. In the rst part of this study, essential logic gates, i.e. Inverter, NAND and NOR, have been implemented using BSIM-CMG devices. After being analyzed and compared with the CMOS technology, a 32% reduction on dynamic power consump- tion and 82% reduction for the leakage current has been obtained. For a compre-hensive look on full adder designs, several novel adder architectures have been im- plemented including ultra low power and minimum number of transistor (10T) de- signs. The analysis of these implementations shows 54% dynamic power reduction, 98% static current reduction and 26% delay reduction. These results lead to a 68% improvement on the Power-Delay product comparing with the 32nm CMOS planar technology. In order to investigate dynamic logic circuits with multi-gate transistors, two recent dynamic circuit techniques have been implemented with novel enhancements to reduce the leakage current. Data Driven Dynamic Logic (D3L) and Split-Path Data Driven Dynamic Logic (SPD3L) have been used to analyze the dynamic logic circuits resulting in 11% reduced dynamic power, 52% reduced leakage current and 33% reduced delay. Second part of this study deals with the independent gate devices. Using the BSIM-IMG model, new XOR/XNOR logic gate designs are introduced for im- plementing novel low-power adders. With these new adder architectures, the average improvement on Dynamic power is an 8% and the designs are 6% faster. Furthermore, a new design technique is proposed combining the possible modes (Short Gate-SG, Low-Power-LP, Independent Gate-IG) that the BSIM-IMG provides. Using this novel mixed design, the Power-Delay product is improved on average 7.2% and 54%, com- pared to the Short-Gate (SG) and Low-Power (LP) modes, respectively. The properties of the BSIM-IMG logic have been applied to improve the Dy- namic logic designs as well. The Domino and SPD3L design techniques have been implemented and enhancements such as merging the pull-up transistors have been proposed for sleep and power-gating techniques. With these enhancements, the Dy- namic power is reduced 13% in average and the designs are 18% faster. The trade-o is an increase on leakage current of 8%. Another major contribution of the work has been the development of shell script les for generating a custom toolbox for datapath designs with multi-gate and independent-gate transistors.
Ph.D. in Electrical and Computer Engineering, July 2015
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Title: EMBEDDED SYSTEM DESIGN FOR TRAFFIC SIGN RECOGNITION USING MACHINE LEARNING ALGORITHMS
Creator: Han, Yan
Date: 2016, 2016-12
Description: Traffic sign recognition system, taken as an important component of an intelligent vehicle system, has been an active research area and it has...
Show moreTraffic sign recognition system, taken as an important component of an intelligent vehicle system, has been an active research area and it has been investigated vigorously in the last decade. It is an important step for introducing intelligent vehicles into the current road transportation systems. Based on image processing and machine learning technologies, TSR systems are being developed cautiously by many manufacturers and have been set up on vehicles as part of a driving assistant system in recent years. Traffic signs are designed and placed in locations to be easily identified from its surroundings by human eyes. Hence, an intelligent system that can identify these signs as good as a human, needs to address a lot of challenges. Here, ―good‖ can be interpreted as accurate and fast. Therefore, developing a reliable, real-time and robust TSR system is the main motivation for this dissertation. Multiple TSR system approaches based on computer vision and machine learning technologies are introduced and they are implemented on different hardware platforms. Proposed TSR algorithms are comprised of two parts: sign detection based on color and shape analysis and sign classification based on machine learning technologies including nearest neighbor search, support vector machine and deep neural networks. Target hardware platforms include Xilinx ZedBoard FPGA and NVIDIA Jetson TX1 that provides GPU acceleration. Overall, based on a well-known benchmark suite, 96% detection accuracy is achieved while executing at 1.6 frames per seconds on the GPU board.
Ph.D. in Computer Engineering, December 2016
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Title: A NANO-STRUCTURED CERAMIC/POLYMER COMPOSITE FILM FOR ELECTRONIC INTERCONNECTIONS
Creator: Harwath, Frank
Date: 2016, 2016-05
Description: Separable electrical interconnections are a ubiquitous part of modern life and for technical reasons are currently based on the use of gold....
Show moreSeparable electrical interconnections are a ubiquitous part of modern life and for technical reasons are currently based on the use of gold. Since gold is a commodity and subject to significant price fluctuations there is a need for separable interconnects not based on gold. Polymer/ceramic films were produced from various polymer precursors with loadings of multi-wall nanotubes (MWNT) and inert fillers. A variety of applications means were employed with the best success being achieved by means of a modified doctor blade. Pyrolysis was conducted in an inert atmosphere at 1 bar at a range of temperatures in a tube furnace. Pyrolysis was also conducted using a fiber laser. The modulus of the film is estimated to be 71.8 MPa with an ultimate tensile strength of 179 MPa based on hardness tests and anisotropic crack dimensions which developed as a result of uniaxial stress induced during application of the precursor. Uniaxial stress improved film adhesion regardless of filler type or level. Modification of film characteristics after pyrolysis was attempted using spark plasma sintering (SPS). Electrical testing displayed a percolation threshold above loadings of 1% (wt) of MWNTs where there is a significant drop in electrical resistivity. Further reductions in contact resistance were demonstrated up to 2% loading of MWNTs. The level of contact resistance achieved (<10) for a separable contact, in conjunction with a gold plated contact representative of most electronic connectors, indicates that an acceptable level of contact resistance may be achieved using these materials. Characterization of the film using attenuated total reflectance (ATR), xray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy point to a morphology which is dominated by crystallites joined by regions of aliphatic carbon chains. Work function measurements were consistent with highly ordered pyrolytic graphite. (HOPG)
Ph.D. in Materials Science and Engineering, May 2016
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Title: EARLY CHILDHOOD RISK FACTORS FOR EXECUTIVE DYSFUNCTION IN A SAMPLE OF SCHOOL-AGED CHILDREN
Creator: Grahovec, Morgan Carey
Date: 2014, 2014-12
Description: The purpose of the present study was to explore whether early childhood factors influence executive function scores, as determined by...
Show moreThe purpose of the present study was to explore whether early childhood factors influence executive function scores, as determined by objective neuropsychological tests and subjective parent and teacher ratings, in a diverse sample of school age children. Data was collected longitudinally over four different visits that corresponded to childhood development (7.76 months, 20 months, 38 months, and 7 years of age). The independent variables examined in the present study included environmental, sociodemographic, and neuropsychological data from the first three time points. At Time 1, the independent variables were SES at Time 1, infant birth weight, maternal body mass index, parental stress at Time 1, and the psychomotor development score at Time 1. At Time 2 and Time 3, the independent variables were SES, parental stress, the sleep problems composite, the DSM-IV ADHD composite, and the psychomotor development index score. Results indicated that overall, maternal pre-pregnancy body mass index, the psychomotor development index score, and family socioeconomic status were the only significant predictors from the first three time points of variance in the Time 4 executive functions as measured by the neuropsychological assessments. The findings showed an inverse relationship between maternal BMI and neuropsychological executive functions, indicating that as BMI increased, executive functioning decreased. A positive relationship between family SES and neuropsychological EF was found, indicating that children from higher SES families performed better on measures of executive functions, as expected. Similarly, a positive relationship was found between psychomotor functions at Time 3 and executive functions at Time 4, which was also in the expected direction. In contrast, subjective parent stress and the DSM-IV ADHD scores were the only significant predictors of the Time 4 executive functions as measured by the parent and teacher ratings. An inverse relationship between parent stress and executive functions was found at all three initial time points, revealing that parents who experience more subjective stress also have children with lower executive functions per parent and teacher report at age 7. A positive relationship was shown between the DSM-IV ADHD composite at Time 3 and the parent/teacher composite score of executive functions at Time 4. This means that children with low executive functions per the parent/teacher composite at Time 4 also had parents and teachers who endorsed greater ADHD symptomatology at Time 3. Subjective parent stress was particularly notable because it was the only independent variable for either of the two dependent variables that was significant across all three of the initial time points. The longitudinal design of this study allowed for the confirmation of the hypothesis that there are significant variables in early childhood that are associated with executive functions later in life. This knowledge has important implications because the more that is understood about executive functioning in children, the more it will be possible to provide meaningful interventions that can maximize a child’s development of this critical skill set.
Ph.D. in Psychology, December 2014
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Title: AN OVERVIEW OF THE APPLICATION OF FIBER REINFORCED POLYMER COMPOSITES IN STRUCTURAL REHABILITATION
Creator: Elhassan Abdelrahman, Aymen Mohamed
Date: 2014, 2014-05
Description: Seismic bridge design practice started in the United States in the mid-1970s. Bridges designed according to pre-1970 design codes may be...
Show moreSeismic bridge design practice started in the United States in the mid-1970s. Bridges designed according to pre-1970 design codes may be seismically vulnerable. This vulnerability is generally because of inadequate reinforcement detailing, which may compromise the strength and ductility of bridge piers, columns and bents. The lack of adequate strength and ductility may lead to bridge failure under seismic loads. Several rehabilitation methods have been used to retrofit the deficient columns and piers so that their performance under potential seismic loads can be improved. Among these methods includes using: (1) concrete jackets; (2) steel jackets; and (3) fiber reinforced polymer composites. The latter method has attracted bridge engineers in recent years because of its easy application and it versatility to be used in bents and columns with non-circular cross sections. The objective of this thesis is to provide a summary of the current practice in using this type of material in bridge retrofit applications. The thesis presents an overview of fiber reinforced polymer (FRP) composite materials behavior and properties, and their composition. Furthermore, the behavior of reinforced concrete columns, when confined with FRP jackets, is reviewed. Available design methods used for determining the FRP jacket thickness and other design properties needed for application in seismic retrofitting of reinforced concrete columns are also reviewed, presented and discussed.
M.S. in Civil Engineering, May 2014
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Title: FRACTURE TOUGHNESS EVALUATION OF FIVE MICROALLOYED PLATE STEELS FOR WIND TOWER APPLICATIONS
Creator: Gaisina, Vladilena
Date: 2015, 2015-05
Description: Five microalloyed plate steels were evaluated for impact and fracture tough- ness. Results at room and low temperatures were compared. These...
Show moreFive microalloyed plate steels were evaluated for impact and fracture tough- ness. Results at room and low temperatures were compared. These steels are com- monly ordered to meet ASTM A572/A709 Grade 50 or EN 10025-2 Grade S355 requirements in the normalized condition for wind tower and other structural ap- plications. One of the ve steels was in the normalized condition, while the rest were left as-rolled. Furthermore, the e ects of carbon content and alloy additions are investigated, with niobium and vanadium as the principal strengthening elements. Impact toughness testing using Charpy V-notch specimens was performed to deter- mine the ductile-to-brittle transition temperature (DBTT). Fracture toughness was measured using the J-integral method. The critical fracture energy Jc was converted to the critical plane strain stress intensity factor KIc if validity requirements were met. Compact tension samples of each steel were tested at room temperature and at -40oC. The results of room temperature tests are compared to those obtained in previous work. The steels with niobium demonstrate signi cantly lower DBTT than vanadium steels. At room temperature, fracture toughness performance is comparable for low carbon grades. Among medium carbon steels, the vanadium one fares slightly better than the as-rolled niobium, with the normalized niobium steel o ering the highest room temperature fracture toughness of the three. Overall, the lower carbon content is noted to provide a signi cant increase in toughness for a modest trade-o in tensile strength.
M.S. in Material Science Engineering, May 2015
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Title: CYCLIC THERMAL TREATMENT
Creator: Gu, Sijie
Date: 2015, 2015-12
Description: Cyclic thermal treatment has the potential to improve energy efficiency of thermal processing. It has been shown that in some cases, the...
Show moreCyclic thermal treatment has the potential to improve energy efficiency of thermal processing. It has been shown that in some cases, the productivity was enhanced by the cyclic thermal treatment operation. In order to investigate the cyclic thermal treatment effect, Copper-Nickel interdiffusion couples were investigated. When the Cu-Ni interdiffusion couple showed positive results, the cyclic thermal treatment was applied to pack carburization and gas carburization of steel. The Cu-Ni interdiffusion couples were annealed with different time-temperature profiles for 5 days. There are three types of time-temperature profile; isothermal, symmetric, and asymmetric cyclic thermal treatment. After thermal treatment, concentration-distance profiles were. Based on the concentration-distance profile, the interdiffusion coefficients of different time-temperature profiles were calculated. The interdiffusion coefficient of the diffusion couple with a ramp rate of 1°C/min had a higher diffusion coefficient than that of the diffusion couple annealed isothermally at the equivalent temperature, 863°C, which means that cyclic thermal treatment has the effect of accelerating diffusion. When the ramp rate was 5ºC/min interdiffusion coefficients were higher than that of the diffusion couple annealed isothermally at the maximum temperature. However, when the ramp rate was increased to 10°C/min, the diffusion coefficient decreased to almost the same as the interdiffusion coefficient of the diffusion couple at the equivalent temperature. After achieving a promising result for the Cu-Ni diffusion couples, we expanded the cyclic thermal treatment to carburizing. The temperature range for cyclic pack carburization was 850° to 950°C. Increasing the cyclic ramp rate resulted in an increase in the case depth. Due to the setup of the pack carburization, the maximum cooling rate achievable is 5°C/min. In order to reach a higher ramp rate, an induction heating gas carburization system was setup. The temperature range for the cyclic induction heat gas carburization was 850°C to 950°C. For the cyclic induction heat gas carburization with increase in ramp rate, the case depth increased. The sample induction gas carburized at a ramp rate of 20°C/min had a deeper case depth than the sample induction gas carburized isothermally at 904.4°C, the equivalent temperature. The first test showed the sample induction gas carburized with a ramp rate of 20°C/min had a deeper case depth than the sample induction gas carburized isothermally at 950° C. With this we draw the conclusion that the cyclic induction gas carburization can achieve a deeper case depth than the isothermal at equivalent temperature induction gas carburization.
Ph.D. in Materials Science and Engineering, December 2015
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Title: POTENTIAL EXPOSURE TO SUBSTANCES IN POLYMER COMPOSITES USED AS FOOD PACKAGING MATERIALS
Creator: Shah, Saloni S.
Date: 2021
Description: In the food manufacturing, preservation, supply, and distribution chain, packaging plays a critical role. The fundamental goal of any...
Show moreIn the food manufacturing, preservation, supply, and distribution chain, packaging plays a critical role. The fundamental goal of any packaging method is to keep food contained and protected. There is an increasing demand for natural and "fresh-like" foods that are less processed and have a longer shelf life, necessitating a variety of packing strategies. With increasing demand, the biggest developments in the field of packaging technology have been innovative food packaging approaches, such as active packaging, intelligent packaging, and bioactive packaging, which include deliberate contact with the food or its surroundings and its effect on consumer health. Several research studies in the past few years have shown that nanocomposite materials have significant improvement in the strength, barrier characteristics, antimicrobial capabilities, and heat and cold stability of food packaging materials, but various studies have reported that these composites might be a source of engineered nanomaterials in the human diet or environment. It has also been reported in numerous studies that nanocomposites can migrate into the food during long-term storage. These studies use food simulants like acetic acid and water to mimic the food matrix. However, they raise issues regarding how ingredients in real foods could affect exposure. This research focuses on the migration of silver (Ag) ions into food matrix-like commercial beverages and demonstrating if the ingredients present in commercial food and beverages influence the migration process. For the study, polymer composites films and dogbones were made. Polymer composite films with 0.2%, 1%, and 5% of silver zeolite concentration in polylactic acid (PLA) were produced, and different media like water, Domino sugar, and Squirt were stored in packages manufactured from this material under accelerated room-temperature conditions. Polymer composite dogbones were made with low-density polyethylene (LDPE) and polypropylene (PP) with 1.25% and 2.51% of graphene and graphite. Further, these materials were characterized with the help of Thermogravimetric analysis (TGA), Fourier Transform Infrared Spectroscopy-Attenuated Total Reflection (FTIR-ATR), and inductively coupled plasma mass spectrometry (ICPMS). This hypothesis of this study was that, when polymer composites are employed in packaging applications, food and beverage components may impact dietary exposure to these particles, and the use of food simulants may underpredict the quantity of the migration in some cases
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Title: Two Essays on Corporate Finance
Creator: Wang, Bo
Date: 2021
Description: This dissertation is comprised of two essays on finance. In the first chapter, I investigate whether and to what extent unionization would...
Show moreThis dissertation is comprised of two essays on finance. In the first chapter, I investigate whether and to what extent unionization would influence the compensation to the non-executive employees. In the second chapter, I explore how social capital would impact regional innovation performance by private firms.In the first chapter, I examine the effects of unionization on stock options granted to non-executive employees. Adopting a regression discontinuity design, I find that employees receive more stock options after the union election wins. The positive association is more pronounced when unions have more bargaining power and when free-riding problems are less severe. Further, I provide evidence that employees receive more stock options when CEOs are entrenched. Finally, I show that stock options provide risk-taking incentives to non-executive employees. This work provides a potential explanation to the union wage premium puzzle that unions utilize stock options to increase non-executive employees’ total compensation. In the second chapter, I investigate whether and to what extent social capital may affect regional innovation by private firms in the U.S. I document that regional social capital is positively associated with the quantity, quality, and novelty of county-level innovation by private firms. This effect is more prominent in regions with a lower supply of financial capital. My findings further suggest that social capital is complementary to investment in research and development. Using a Spatial Durbin Model, I report that regional social capital has significant spillover effects in boosting the innovation of neighboring counties.
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Title: IRREGULAR GROWTH AND INTERFACIAL EFFECT IN THIN FILM MULTILAYER STRUCTURES FOR USES IN PHOTOCATHODE APPLICATIONS
Creator: Lee, ZhengRong
Date: 2021
Description: Improving photocathode performance by increasing the electron density while lowering the angular spread of emitted electrons can improve...
Show moreImproving photocathode performance by increasing the electron density while lowering the angular spread of emitted electrons can improve particle accelerator performance, expanding the reach of both fundamental and applied science. Materials science expertise is needed to design new photocathodes with these desired properties. Nemeth, et al, determined that a multilayered photocathode structure consisting of MgO/Ag/MgO could be engineered for higher brightness and lower dispersion [Nemeth, et al, Phys. Rev. Lett. 104, 046801 (2010)]. The dispersion of the surface bands impacts the angular spread of the emitted beam, and the model predicted that the bands could be tuned by precisely controlling the layer thicknesses of the multilayer structure. We synthesized and probed this MgO/Ag/MgO system experimentally. We measured the work function, emittance, and quantum efficiency of multilayer photocathodes with different MgO layer thicknesses to compare with theoretical predictions. We observed that although the general trend was as predicted, the measurements and the model were not in exact agreement [Velasquez, et al, Appl. Surf. Sci. 360, 762 (2016)]. In this work, we have undertaken a study of the electronic structure of the interfaces to explore how these observed deviations may have originated. It is possible that the fabrication process leads to non-ideal interfaces compared to those constructed in the simulations. To study how the fabrication affects the interfaces, hard X-ray photoemission spectroscopy(HAXPES) was used to probe the chemistry of the buried interfaces within the thin film multilayer structure of Ag and MgO. In these multilayer structures, we observed that the silver layers were predominantly metallic. A small high binding energy (ΔE = 0.69 eV) peak was also observed in the Ag 3d core level in the samples. This peak is shifted in the opposite direction of the binding energy shift in silver oxides, suggesting that this peak is not due to the formation of silver oxides at the interfaces with the MgO. Two possible explanations for the origin of this peak then are charge transfer at the interface from the Ag to the oxide monolayer or the formation of silver nanoparticles during the growth process. Based upon simple depth profiling analysis, we postulate the former is the more likely explanation. In addition, the O 1s and Mg 1s core level indicated the presence of Mg(OH)2. The MgO layers react with H2O in the vacuum chamber or ideal gas used as a buffer during sample transfer. Since the theory predicts a strong dependence upon the number of MgO layers surrounding the Ag, the formation of Mg(OH)2 likely contributes to the non- ideal behavior, even given the similarity in the electronic structure to MgO (large band gap insulator) and Mg(OH)2. The speed at which this reaction occurs would significantly limit the lifetime and the utility of the MgO/Ag multilayer photocathodes. In order to custom engineer multilayer photocathodes, complete control over the growth process will be needed to ensure that the ideal surfaces are formed. Using non-reactive materials would greatly increase the lifetime of the engineered photocathodes.
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Title: SPECIFICITY OF DEFICITS IN EXECUTIVE FUNCTIONING IN YOUTH WITH NONVERBAL LEARNING DISABILITY, ATTENTION DEFICIT HYPERACTIVITY DISORDER AND READING DISORDER
Creator: McCue, Kimberly Ann
Date: 2021
Description: Nonverbal Learning Disability (NLD) has been the focus of four decades of neuropsychological research. However, it has yet to be included as a...
Show moreNonverbal Learning Disability (NLD) has been the focus of four decades of neuropsychological research. However, it has yet to be included as a diagnostic category in the Diagnostic and Statistical Manual of Mental Disorders (i.e., currently in its fifth edition, DSM-5, American Psychiatric Association, 2013). Many of the characteristics associated with Nonverbal Learning Disorder (NLD) are similar to those found in other more established disorders such as Attention-Deficit/Hyperactivity Disorder (ADHD), Specific Learning Disorders (SLD), and Autism Spectrum Disorder (ASD). Recent research in neuropsychology and other fields has contributed to a greater understanding of the cognitive profiles of NLD, ADHD, and Reading Disorder (RD). However, the neurological underpinnings of deficits in executive functioning specific to NLD versus ADHD and RD have yet to be fully elucidated. Ongoing research has failed to distinguish NLD from other childhood disorders, including ADHD, based on specific structural or functional neurological deficits. The current study examined the specificity of deficits in executive functioning in youth with nonverbal learning disability, attention deficit hyperactivity disorder and reading disorder. In addition, the study examined the degree to which the Rey Complex Figure Test subscales and Processing Speed Index (PSI) and Working Memory Index (WMI) scores (WISC-IV or WISC-III) could discriminate between the NLD group from ADHD and RD groups. Data for the present study were collected from a population served by the Pediatric Neuropsychological Service at The University of Chicago Medicine. Children who had been referred for neuropsychological assessment and whose comprehensive battery included a WISC measure (WISC-III or WISC-IV) and RCFT measurements were included. All data were archival, i.e., gleaned from the Service database; data from 202 participants was retrieved, including youth who underwent neuropsychological evaluation between 2003 and 2016. The present study hypothesized differences between NLD, ADHD, and RD diagnostic groups on visuo-spatial planning/organization, visuo-spatial working memory, long-term visuo-spatial recall, visuo-spatial recognition, verbal working memory, and processing speed. In summary, of the six executive function domains examined, two domains showed significant underperformance for the NLD group, two domains showed a non-significant trend of underperformance for the NLD group and two domains did not show significant differences between diagnostic groups.
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Title: BURNOUT AMONG SEXUAL MINORITIES: THE ROLE OF CONCEALMENT, RUMINATION, AND ORGANIZATIONAL NON-DISCRIMINATION POLICIES
Creator: Burke, Margaret
Date: 2021
Description: Employee burnout is detrimental to individuals (e.g., physical and mental health concerns), as well as to organizations (e.g., diminished...
Show moreEmployee burnout is detrimental to individuals (e.g., physical and mental health concerns), as well as to organizations (e.g., diminished performance). Although numerous studies have examined burnout across a variety of industries and populations, there are limited studies that have examined burnout specifically among sexual minority employees, referring to lesbian, gay, bisexual, transgender, and queer (LGBTQ) workers. This study integrated Meyer’s (2003) Minority Stress Model and Hatzenbuehler’s (2009) Psychological Mediation Framework to investigate the role of concealment, rumination, and non-discrimination organizational policies on burnout among 406 sexual minority employees working in a variety of industries (e.g., healthcare, retail, education, etc.). To test the relationships between these variables, a mediation model and a mediation with moderation model was tested using Hayes’ (2018) Process macro. Results indicated that concealing one’s sexual orientation at work was positively related to rumination, and in turn, was positively related to burnout. Contrary to one of the hypotheses, organizational non-discrimination policies that were inclusive of sexual minorities did not moderate the relationship between concealment and burnout. Previous research, implications, and limitations to this study are discussed in detail.
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Title: Computational study on the heme scavenging ability of Staphylococcus aureus IsdH receptor: Utilizing molecular dynamics to understand an unknown mechanism
Creator: Clayton, Joseph Alan
Date: 2021
Description: Methicillin-resistant Staphylococcus aureus (MRSA) has become an infamous pathogen with infection rates that have declined slowly in recent...
Show moreMethicillin-resistant Staphylococcus aureus (MRSA) has become an infamous pathogen with infection rates that have declined slowly in recent years. S. aureus requires iron as a metabolic nutrient during infection and obtains this nutrient through an iron-regulated surface-determinant (Isd) system that extracts iron from the host’s heme stored in hemoglobin (Hb) through near iron transporter (NEAT) domains. This work concentrates on studying the second and third NEAT domains of IsdH by utilizing atomistic molecular dynamics to probe the heme scavenging process; in collaboration with the Clubb Group at UCLA, we discover key functional regions of IsdH and describe fundamental interdomain dynamics. In addition, I investigate a conventional computational method to describe protein dynamics and propose an alternative that aims to alleviate computational effort by incorporating experimental data.
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Title: INVESTIGATION OF STRUCTURE AND PROCESSING EFFECTS ON THE ELECTROCHEMICAL PERFORMANCE OF COBALT-FREE, LITHIUM- AND MANGANESE-RICH LAYERED OXIDE CATHODE FOR LIBS
Creator: Kucuk, Kamil
Date: 2021
Description: Rechargeable Li-ion batteries (LIBs) have been widely used in a diverse range of energy storage systems because of their high energy and power...
Show moreRechargeable Li-ion batteries (LIBs) have been widely used in a diverse range of energy storage systems because of their high energy and power density, low self-discharge, and tolerable memory effect, compared to the conventional alkaline, lead acid, and nickel-cadmium (Ni/Cd) batteries. [2] Since not only cathodes materials control the energy density of a cell, but also the capacity of cathode material characteristically restricts the cell capacity (as well as about 40% of the cell cost results from the cost of cathode raw materials), the majority of studies on LIBs have been carried out on developing alternative cathodes with higher energy, lower cost, and more environmentally friendliness. [2], [3] From this perspective, both Co-free and lithium- & manganese-rich (LMRO) layered oxide MNF cathodes, Li1.2(MnxNiyFez)O2, have recently attracted great attention in lithium-ion battery (LIB) research for electric vehicles and energy storage devices due to their high capacities of over 250 mAhg−1 and being eco-friendly and inexpensive compared to the cobalt-based Li-rich Li1.2(NixMnyCoz)O2 and Ni-rich Li(NixMnyCoz)O2 (NMC), and LiCoO2 commercial cathodes. Replacing toxic and expensive Co in the LMRO cathodes with environmentally friendly and much cheaper Fe element has been extensively studied over the last two decades. It was suggested by Aryal, S. et. al., in 2018. [4] that the Li1.2(Mn0.50Ni0.20Fe0.10)O2 (MNF502010) Co-free LMRO MNF cathodes seem better in terms of capacity-retention with higher discharge capacity and less voltage fade compared to other MNF compositions. However, the MNF502010 cathode still suffers from its lower experimental capacity, compared to its expected theoretical capacity (270-455 mAhg−1), as well as capacity decay, voltage fade, poor rate capability, and thermal instability. In this dissertation, it is reported that comparable specific discharge capacity with less amount of voltage fading and capacity decay can be achieved by fluorine doping, synthesizing materials in large amounts (0.1 mol synthesis at least) with two-step firing, and then washing the obtained nanocomposites with H3PO4 to create Li3PO4 layer on the surface of bulk MNF composites. The specific discharge capacity and cycling performance of the Co-free MNF502010 cathodes were studied and enhanced by using and optimizing these approaches in this work for the first time. However, voltage fading and capacity decay are still remaining challenges, even if they are remarkably mitigated by applying these approaches. Structural changes due to layered to spinel transformation, less amount of monoclinic phase activation leading to structural deformation occurring after 1st charge, dissolution of the transition metals (TM), and oxygen release (loss of lattice oxygen) from the MNF material upon following electrochemical cycling at higher voltage (≥ 4.5V ) seem the main reasons behind these challenges, specifically the voltage fading and capacity decay.A series of fluorine-doped/undoped, Co-free MNF502010 nanocomposite cathode materials (Li1.2(Mn0.50Ni0.20Fe0.10)O2(1−x)F2x, briefly F-doped MNF) were synthesized by using a sol-gel technique. Firstly (Chapter 4), the fluorine was substituted for oxygen in the parent MNF compound in different fractions (0.00, 0.025, 0.05,0.075, 0.10, which means 0%, 2.5%, 5.0%, 7.5%, and 10%), in order to optimize the amount of fluorine for better performance; secondly (Chapter 5), a large batch (0.1mol, 10 times more than the previous batch) of 5%F-doped material was prepared by a modified sol-gel synthesis which is modified by heating at 700 ◦C for different time-periods; 7.5 hours (7.5h), 15 hours (15h, two-step firing, 7.5h + rest for 12h + 7.5h), instead of heating directly 15 hours (d15h), as done in the first chapter; finally (Chapter 6), H3PO4 treatment resulting in a non-uniform Li3PO4 layer on the bulk surface. These approaches were respectively applied on doped/undoped MNF502010 nano-composites, in order to overcome the challenges already mentioned above. Finally, the effects of these approaches on the structural, morphological, and electrochemical properties of MNF cathode materials were investigated by means of powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray (EDS) analysis, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic charge-discharge cycling, and X-ray absorption spectroscopy (XAS, an element specific probe technique). Specifically, ex-situ XAS was performed at the Mn, Ni, and Fe K-edge and used to detect the changes both in the oxidation state of the transition metal (TM) ions and their local environments in order to get a better understanding of the improved performance of the composite materials, as well as their failure mechanism. Moreover, the EXAFS data were modeled to gain insight into the influence of these approaches on the electrochemical performance of both pristine (uncycled) and cycled electrodes (after the 100th discharge). From correlating the electrochemical performance of the modified/unmodified MNF nano-composite cathodes to their XANES and EXAFS analysis, the ability to achieve higher specific capacity is strongly dependent on the formation of a well-ordered layered structure and the amount of monoclinic component (Li2MnO3) activation resulting in higher redox-activity of the Mn cations. The long-term cyclability or capacity retention can be enhanced by heating the resulting powders with a two-step firing (instead of directly 15 hours) and washing them with 1wt%H3PO4 solution to create a Li3PO4 conductive and protective layer.
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Title: A three-dimensional tissue molecular imaging system based on angular domain optical projection tomography: Applications in lymph node biopsy
Creator: Torres, Veronica Calliste
Date: 2020
Description: Sentinel lymph node biopsy is a good prognostic factor for several cancers as therapeutic decisions are often determined by the results....
Show moreSentinel lymph node biopsy is a good prognostic factor for several cancers as therapeutic decisions are often determined by the results. Despite this importance, false negatives remain common because of standard pathology procedures that aim only to detect macrometastases (> 2 mm diameter) and leave more than 99% of lymph node volumes unassessed. While it is possible to section tissue samples more thoroughly, a subsequent 10x increase in pathologist read time is undesirable. Therefore, a more sensitive and rapid approach for lymph node evaluation is warranted.Our proposed solution was the development of an angle-restricted optical projection tomography system to provide high resolution quantitative imaging of whole lymph nodes prior to conventional pathology. Two main strategies were employed: 1) early photon imaging achieved with angular restriction to minimize the number of detected multiply scattered photons that add to imaging blur; and 2) paired-agent molecular imaging, which can quantify targeted biomolecule concentrations through co-administration of targeted and control imaging agents.This thesis focused primarily on the first aspect; however, all work was performed with paired-agent imaging in mind, such that the technique can be implemented directly in future studies. The first chapter presents a proof-of-concept that verifies the utility of angle-domain imaging for evaluation of low scattering lymph nodes. Filtered backprojection and strict angle restriction for scatter rejection were sufficient to detect and localize clinically relevant metastases. In the second chapter, improvements were made to the system so that detection efficiency could be improved, and the system was more rigorously characterized in terms of reconstruction accuracy and limits of detection. Finally, the third chapter presents the investigation of alternate reconstruction techniques to push the limits of achievable resolution and image quality. The overall findings of this work demonstrate the potential for an angle-restricted tomography system to provide significant improvements of metastases detection sensitivity in excised lymph nodes compared to conventional pathology at a fraction of the time and cost.
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Title: FIELD EMISSION MITIGATION VIA IN-SITU PLASMA PROCESSING IN 1.3 GIGAHERTZ 9-CELL LCLS-II CAVITIES
Creator: Giaccone, Bianca
Date: 2021
Description: Field emission (FE) is one of the limiting factors in superconducting radiofrequency cavities' performance. It is known that even a few...
Show moreField emission (FE) is one of the limiting factors in superconducting radiofrequency cavities' performance. It is known that even a few monolayers of surface adsorbed contaminants can lower the niobium work function and increase the FE. In order to address the field emission that may arise once the accelerator is already assembled, it was decided to develop plasma processing for the Linac Coherent Light Source II, a method to mitigate field emission in-situ. Starting from Doleans's successful experience with plasma processing for high beta cavities, Fermi National Accelerator Laboratory is developing plasma cleaning for TESLA shaped 1.3 GHz 9-cell cavities. A new method of ignition based on the higher order modes and couplers was developed, along with a detection procedure that allows to identify the location of the plasma inside the cavity. In this work are presented the results of plasma processing applied to 1.3 GHz cavities, both single-cell and 9-cells. The cavities were contaminated with multiple sources, naturally or artificially, and their performance was measured through cryogenic RF tests before and after plasma cleaning. These experiments proved that plasma processing successfully removed hydrocarbon-related field emission from cavities artificially contaminated, but also from a cavity with natural and unknown FE source. In some cases of more extreme contamination through vacuum failure simulation conducted in air (not in a cleanroom), plasma processing was not able to recover the cavity's performance. An ongoing analysis of the cavity contaminants is presented here, explaining the reason why some contaminated cavities showed little improvement after plasma processing. A microscopic study of the effect of plasma processing on the niobium surface is also presented. Niobium samples prepared with different surface treatments were analyzed using X-ray photoelectron spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The samples were subjected to plasma processing and analyzed again, in order to draw a comparison and identify possible surface changes caused by the reactive oxygen contained in the glow discharge. The samples were prepared with different surface treatments in order to understand if plasma processing may affect them differently. This study showed a possible increase in the oxide thickness after plasma processing and a reduction of the energy difference between the pentoxide and the metal peaks. In preparation for this study, the near-surface region of one niobium sample was investigated with X-ray photoelectron spectroscopy at various steps of sputtering and subsequent oxide regrowth in air. The results showed that the majority of the oxide is composed of Nb2O5, however, the presence of two suboxides (NbO, NbO2) is observed, plus an additional peak (attributed to Nb2O) measured both during sputtering and oxide regrowth.
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Title: Moksha Tower
Creator: Fu, Yalin
Date: 2011-03, 2010-05
Description: In India, death is considered one of the most important stages of the whole human process.And the traditional funeral process occupied a great...
Show moreIn India, death is considered one of the most important stages of the whole human process.And the traditional funeral process occupied a great quantity of land in a country with a big population.Moksha tower(cemetery tower) created a high-rise cemetery in order , to free up previous ground floor cemetery green space for recreation. This would create a vertical resource for the handling and disposal of dead bodies, which would provide storage for the dead for only limited a period of time, in order to ensure adequate capacity to continually accommodate new dead.
Sponsorship: Wood, Antony
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