Search results

Title: MICROGRIDS AND DISTRIBUTED GENERATION SYSTEMS: CONTROL, OPERATION,COORDINATION AND PLANNING
Creator: Che, Liang
Date: 2015, 2015-07
Description: Distributed Energy Resources (DERs) which include distributed generations (DGs), distributed energy storage systems, and adjustable loads are...
Show moreDistributed Energy Resources (DERs) which include distributed generations (DGs), distributed energy storage systems, and adjustable loads are key components in microgrid operations. A microgrid is a small electric power system integrated with onsite DERs to serve all or some portion of the local loads and connected to the utility grid through the point of common coupling (PCC). Microgrids can operate in both gridconnected mode and island mode. The structure and components of hierarchical control for a microgrid at Illinois Institute of Technology (IIT) are discussed and analyzed. Case studies would address the reliable and economic operation of IIT microgrid. The simulation results of IIT microgrid operation demonstrate that the hierarchical control and the coordination strategy of distributed energy resources (DERs) is an effective way of optimizing the economic operation and the reliability of microgrids. The benefits and challenges of DC microgrids are addressed with a DC model for the IIT microgrid. We presented the hierarchical control strategy including the primary, secondary, and tertiary controls for economic operation and the resilience of a DC microgrid. The simulation results verify that the proposed coordinated strategy is an effective way of ensuring the resilient response of DC microgrids to emergencies and optimizing their economic operation at steady state. The concept and prototype of a community (networked) microgrid that interconnecting multiple microgrids in a community are proposed. Two works are conducted. For the coordination, novel three-level hierarchical coordination strategy to coordinate the optimal power exchanges among neighboring microgrids is proposed. For the planning, a multi-microgrid interconnection planning framework using probabilistic minimal cut-set (MCS) based iterative methodology is proposed for enhancing the economic, resilience, and reliability signals in multi-microgrid operations. The implementation of high-reliability microgrids requires proper protection schemes that effectively function in both grid-connected and island modes. This chapter presents a communication-assisted four-level hierarchical protection strategy for highreliability microgrids, and tests the proposed protection strategy based on a loop structured microgrid. The simulation results demonstrate the proposed strategy to be an effective and efficient option for microgrid protection. Additionally, microgrid topology ought to be optimally planned. To address the microgrid topology planning, a graph-partitioning and integer-programming integrated methodology is proposed. This work is not included in the dissertation. Interested readers can refer to our related publication.
Ph.D. in Electrical and Computer Engineering, July 2015
Show less

Title: NUMERICAL MODELING AND ANALYSIS OF CAVITATION IN WATER AND LASER-INDUCED PLASMA AMPLIFICATION FOR MICROMACHINING APPLICATIONS
Creator: Dabir-moghaddam, Navid
Date: 2017, 2017-05
Description: Machining processes are needed in many industrial areas. Laser-based machining often has the advantages such as high spatial resolution, no...
Show moreMachining processes are needed in many industrial areas. Laser-based machining often has the advantages such as high spatial resolution, no mechanical tool wear, etc., and has current and potential applications in many areas. The objective of this research work is to conduct physics-based modeling studies to help the understanding of some physical processes relevant to two novel laser-based machining processes: (i) the Ultrasound-assisted water-confined laser micromachining (UWLM) process (proposed by Prof. Benxin Wu), and (ii) the Dual-pulse laser ablation and plasma amplification (LAPA) process for drilling microholes with variable diameters at different depths (proposed by Prof. Yung C. Shin). The models are developed by numerically solving the relevant governing equations, and are tested by comparing with related experimental measurements when available. The specific topics that have been studied include: (i) Bubble evolution close to a solid boundary; (ii) Ultrasound propagation and cavitation in water; (iii) Laser amplification of pre-existing plasma in a microhole and plasma interaction with the hole sidewall.
Ph.D. in Mechanical and Aerospace Engineering, May 2017
Show less

Title: XAFS STUDIES OF RADIATION DAMAGE IN NUCLEAR MATERIALS
Creator: Olive, Daniel Thomas
Date: 2012-11-13, 2012-12
Description: The growing demand for nuclear energy places a high importance on the development of new materials capable of withstanding higher temperatures...
Show moreThe growing demand for nuclear energy places a high importance on the development of new materials capable of withstanding higher temperatures and harsher irradiation conditions than those used in existing reactors. By supporting the development of next generation reactors it also becomes possible to close the nuclear fuel cycle, greatly reducing the amount of waste sent for disposal in deep geologic repositories, where its interaction with the environment is also a matter of interest. In this thesis, X-ray absorption fine structure (XAFS) spectroscopy is used to investigate the local atomic structure of systems of interest to nuclear energy. First, two XAFS studies on environmental materials are presented. Granular activated carbon (GAC) was treated with iron to improve its water remediation properties, specifically with respect to arsenic. XAFS was used to determine the nature of iron coating on the GAC surface, and the method of arsenic bonding to the treated surface. Next, a neodymium precipitate from solubility studies carried out for the Waste Isolation Pilot Plant (WIPP) was analyzed. Neodymium was used as an analog for plutonium in brine solutions. XAFS fitting indicated that the neodymium substituted for calcium in a gypsum lattice, providing information useful for future geochemical modeling. XAFS was also used to study radiation damage in materials. A candidate material for advanced reactor structural materials, modified 9Cr–1Mo, was irradiated to 1, 4, and 10 displacements per atom (dpa). XAFS analyses were performed on the Fe, Mo, and Nb K-edges. Irradiation caused a reduction in coordination for all three elements, but the exact behavior was element specific. Damage around Fe atoms was linear with dose, while damage around xxii Mo atoms saturated at or before 1 dpa. XAFS was shown to provide a useful atomic level description of radiation damage for a complex alloy system. Finally, zirconium carbide and zirconium nitride, candidate materials for advanced fuel claddings were studied at the Zr K-edge. Samples irradiated to 1 dpa retained overall crystallinity, as indicated by transmission electron microscopy (TEM) images but were found to have an increase in dislocation loops compared to their non-irradiated counterparts. XAFS analysis was able to determine the size of the undefected regions, making it a valuable complement to other analysis techniques. xxiii
PH.D in Physics, December 2012
Show less

Title: EFFECTS OF VORINOSTAT AND 17-AAG ON THE ANDROGEN RECEPTOR AND ANDROGEN-INDEPENDENT PROSTATE CANCER CELL SURVIVAL
Creator: He, Di
Date: 2012-10-10, 2012-12
Description: Prostate cancer is one of the leading causes of cancer-related deaths. The AR is known to play an important role in cell proliferation and...
Show moreProstate cancer is one of the leading causes of cancer-related deaths. The AR is known to play an important role in cell proliferation and cell survival during the development of prostate tumors. Chemical and physical removal of androgens is therefore commonly used to treat prostate cancer. AR regulatory drugs, such as Vorinostat and 17-AAG, are FDA-approved drugs designed to down-regulate AR expression and suppress tumor growth. However, the function of the AR in post-castration tumors is not clear. Recently, our laboratory and others have shown that the AR also has a pro-death function, especially in androgen-independent prostate cancer cells. To determine the function of Vorinostat and 17-AAG on AR expression levels and cell survival in androgen-independent prostate cancer cells, we treated 104-R1 cells, an androgen-independent prostate cancer cell sub-line, with either Vorinostat or 17-AAG. We found that both drugs down-regulated AR protein levels, although Vorinostat was more potent than 17-AAG. Neither drug independently caused significant cell death; however, at certain doses, both drugs induced cell morphological changes that correlated with AR expression levels. Interestingly, Vorinostat synergized with Adriamycin, a commonly used chemotherapeutic drug, to induce cell death, while 17-AAG suppressed Adriamycin-induced apoptosis in 104-R1 cells. These data suggest that the drugs that are effective for androgen-dependent prostate cancer might not be suitable for androgen-independent prostate cancer.
M.S. in Biology, December 2012
Show less

Title: WORKPLACE MISTREATMENT, AFFECT, AND THE SEXUAL MINORITY EXPERIENCE
Creator: Discont, Steve
Date: 2017, 2017-07
Description: This study investigates the impact of low-intensity workplace mistreatment on affective outcomes for sexual minority workers. The study was...
Show moreThis study investigates the impact of low-intensity workplace mistreatment on affective outcomes for sexual minority workers. The study was grounded in affective events theory and minority stress theory. Data was composed of survey responses from a convenience sample of 380 U.S. adults who work full-time and identify as sexual minorities. Hierarchical multiple regression analyses revealed workplace incivility and heterosexist microaggressions significantly predicted negative discrete emotional reactions (i.e., anger, disgust, fear, guilt and sadness). Internalized heterosexism moderated the predictor-outcome relationship between incivility and affective disgust, and between heterosexist microaggressions and affective anger, disgust, and sadness, such that individuals with low internalized heterosexism had greater negative outcomes when forms of mistreatment were high. Results are discussed in terms of both their theoretical implications, and practical implications for organizational research and practice.
M.S. in Psychology, July 2017
Show less

Title: AN EFFORT TO DISCOVER NOVEL BACTERIAL DSZ GENES TO HELP IMPROVE THE BIODESULFURIZATION OF CRUDE OIL
Creator: Salazar, Joelle Krieger
Date: 2011-04-25, 2011-05
Description: In this thesis study, soil samples were procured from various locations thought to contain high petroleum content, such as gas stations. Those...
Show moreIn this thesis study, soil samples were procured from various locations thought to contain high petroleum content, such as gas stations. Those samples were enriched for those that contained bacteria that were able to metabolize sulfur-containing compounds, such as DBT. The bacteria were then subjected to various experiments to determine if they possess any or all of the genes (dsz) encoding the three enzymes of the dibenzothiophene desulfurization pathway, as compared with R. erythropolis IGTS8. This feat was accomplished by using both growth experiments on medium containing dibenzothiophene as the sole sulfur source and genomic DNA extraction followed by PCR with dszABC universal primers. The resultant amplified DNA was then ligated to pGEM®-T Easy vector and transformed into electrocompetent E. coli cells. The transformants were subsequently screened and sent for sequencing. Using Blast, the sequences were analyzed. No obvious dsz homologies were identified although homologues in some cases to enzymes involved in sulfur metabolism were found. Several isolates were found to have dsz-like activity via the growth experiments as well as the Gibbs assay, which measures accumulation of the end product of the dsz-encoded pathway, 2-HBP Soil sample #32 showed promise in growth experiments in that the culture grew well in M9 with DBT as the sole sulfur source at temperatures of 30 °C, 37 °C, 45 °C, and 55 °C. Streaking the culture discovered two colonies with distinct morphology that were designated 32-W and 32-Y, for white and yellow colonies. 32-W and 32-Y also grew independently in M9 with DBT. Positive Gibbs Assays were obtained from the cultures 32-mixed, 32-W, and 32-Y.
M.S. in Biology, May 2011
Show less

Title: CURRENT TRENDS IN WINDSTORM IMPACT REDUCTION
Creator: Cutter, Brad
Date: 2012-04-14, 2012-05
Description: Natural disasters effect everyday life not only immediately after the event but long after the community has rebuilt. Since the ultimate goal...
Show moreNatural disasters effect everyday life not only immediately after the event but long after the community has rebuilt. Since the ultimate goal of the structural engineer is predicated on life safety, it would be irresponsible to allow the damages of the 2011 tornado season to go unaddressed. Appropriate research and development must be made into a priority for the governing bodies in charge of funding these activities. The data collected from the 2011 season should be more than enough to raise awareness to those responsible for such decisions. The first portion of this study is dedicated to elaborating on the past developments, current advancements, and speculating on future trends of governing standards. It is also helpful to associate these trends alongside data resulting from seismic activities in our nation, which we know to have great success in numbers. Current tendencies are revealed through a case study of (3) elementary schools built in the aftermath of a disaster stricken community in Flint, Michigan. Seismic provisions found its’ greatest breakthrough following the Long Beach Earthquake of 1933, where it was deemed federal law that all schools must uphold the standard that their structures are capable of withstanding earthquake forces. There should be no doubt that this would similarly prove to be a critical first step in protecting children in communities subjected to high-wind forces. If the successes of seismic provisions have any indication on the possibilities of properly funded research and development, then there should countless lessons to be learned across the range of topics covered here. With the incorporation of a federally funded network of facilities and better research data to rely on, design professionals can begin utilizing more adequate connection details into their structures. It is this top-down approach toward change that should move us closer toward creating sufficient design standards and in effect hitting the main objective of this profession, life safety.
M.S. in Civil, Architectural, and Environmental Engineering, May 2012
Show less

Title: PHYSICS OF LIMITING PHENOMENA IN SUPERCONDUCTING MICROWAVE RESONATORS: VORTEX DISSIPATION, ULTIMATE QUENCH AND QUALITY FACTOR DEGRADATION MECHANISMS
Creator: Checchin, Mattia
Date: 2016, 2016-12
Description: Superconducting niobium accelerating cavities are devices operating in radiofrequency and able to accelerate charged particles up to energy of...
Show moreSuperconducting niobium accelerating cavities are devices operating in radiofrequency and able to accelerate charged particles up to energy of tera-electron-volts. Such accelerating structures are though limited in terms of quality factor and accelerating gradient, that translates—in some cases—in higher capital costs of construction and operation of superconducting rf accelerators. Looking forward for a new generation of more affordable accelerators, the physical description of limiting mechanisms in superconducting microwave resonators is discussed. In particular, the physics behind the dissipation introduced by vortices in the superconductor, the ultimate quench limitations and the quality factor degradation mechanism after a quench are described in detail. One of the limiting factor of the quality factor is the dissipation introduced by trapped magnetic flux vortices. The radio-frequency complex response of trapped vortices in superconductors is derived by solving the motion equation for a magnetic flux line, assuming a bi-dimensional and mean free path-dependent Lorentzian-shaped pinning potential. The resulting surface resistance shows the bell-shaped trend as a function of the mean free path, in agreement with the experimental data observed. Such bell-shaped trend of the surface resistance is described in terms of the interplay of the two limiting regimes identified as pinning and flux flow regimes, for low and large mean free path values respectively. The model predicts that the dissipation regime—pinning- or flux-flow-dominated—can be tuned either by acting on the frequency or on the electron mean free path value. The effect of different configurations of pinning sites and strength on the vortex surface resistance are also discussed. Accelerating cavities are also limited by the quench of the superconductive state, which limits the maximum accelerating gradient achievable. The accelerating field limiting factor is usually associated to the superheating field, which is intimately correlated to the penetration of magnetic flux vortices in the material. Experimental data for N-doped cavities suggest that uniform Ginzburg-Landau parameter cavities are statistically limited by the lower critical field, in terms of accelerating gradient. By introducing a Ginzburg-Landau parameter profile at the cavity rf surface—dirty layer—the accelerating gradient of superconducting resonators can be enhanced. The description of the physics behind the accelerating gradient enhancement as a consequence of the dirty layer is carried out by solving numerically the Ginzburg-Landau equations for the layered system. The enhancement is showed to be promoted by the higher energy barrier to vortex penetration, and by the enhanced lower critical field. Another serious threat to the quality factor during the cavity operation is the extra dissipation introduced by the quench. Such quality factor degradation mechanism due to the quench, is generated by the trapping of external magnetic flux at quench spot. The purely extrinsic origin of such extra dissipation is proven by the impossibility of decrease the quality factor by quenching in a magnetic field-free environment. Also, a clear relation of the dissipation introduced by quenching to the orientation of the applied magnetic field is observed. The full recover of the quality factor by re-quenching in compensated field is possible when the trapped flux at the quench spot is modest. On the contrary, when the trapped magnetic flux is too large, the quality factor degradation may become irreversible by this technique, likely due to the outward flux migration beyond the normal zone opening during the quench.
Ph.D. in Physics, December 2016
Show less

Title: END-TO-END WIRELESS DIGITAL COMMUNICATION SYSTEM OF FPGA BASED SOFTWARE DEFINED RADIO
Creator: Dang, Tuan
Date: 2017, 2017-05
Description: This thesis describes the design and implementation of an End-to- End digital wireless communication system (E2E) system on the ZedBoard Zynq...
Show moreThis thesis describes the design and implementation of an End-to- End digital wireless communication system (E2E) system on the ZedBoard Zynq-7000 Field Pro- grammable Gate Array (FPGA) Development Board with an Analog Devices AD9364 Wideband Transceiver from a model-based design system. Furthermore, we present the design path to reconfigure the software controlled logic blocks for additional functionality such that the E2E system could be rapidly redeployed. A comparison BER vs. distance plot between the QPSK-1/2 and uncoded QPSK shows QPSK-1/2 with BER = 0 up to 14 m while no FEC QPSK has minimum BER ~ 10-5 up to the same distance.
M.S. in Electrical Engineering, May 2017
Show less

Title: Utilizing Concurrent Data Accesses for Data-Driven and AI Applications
Creator: Lu, Xiaoyang
Date: 2024
Description: In the evolving landscape of data-driven and AI applications, the imperative for reducing data access delay has never been more critical,...
Show moreIn the evolving landscape of data-driven and AI applications, the imperative for reducing data access delay has never been more critical, especially as these applications increasingly underpin modern daily life. Traditionally, architectural optimizations in computing systems have concentrated on data locality, utilizing temporal and spatial locality to enhance data access performance by maximizing data and data block reuse. However, as poor locality is a common characteristic of data-driven and AI applications, utilizing data access concurrency emerges as a promising avenue to optimize the performance of evolving data-driven and AI application workloads.This dissertation advocates utilizing concurrent data accesses to enhance performance in data-driven and AI applications, addressing a significant research gap in the integration of data concurrency for performance improvement. It introduces a suite of innovative case studies, including a prefetching framework that dynamically adjusts aggressiveness based on data concurrency, a cache partitioning framework that balances application demands with concurrency, a concurrency-aware cache management framework to reduce costly cache misses, a holistic cache management framework that considers both data locality and concurrency to fine-tune decisions, and an accelerator design for sparse matrix multiplication that optimizes adaptive execution flow and incorporates concurrency-aware cache optimizations.Our comprehensive evaluations demonstrate that the implemented concurrency-aware frameworks significantly enhance the performance of data-driven and AI applications by leveraging data access concurrency.Specifically, our prefetch framework boosts performance by 17.3%, our cache partitioning framework surpasses locality-based approaches by 15.5%, and our cache management framework achieves a 10.3% performance increase over prior works. Furthermore, our holistic cache management framework enhances performance further, achieving a 13.7% speedup. Additionally, our sparse matrix multiplication accelerator outperforms existing accelerators by a factor of 2.1.As optimizing data locality in data-driven and AI applications becomes increasingly challenging, this dissertation demonstrates that utilizing concurrency can still yield significant performance enhancements, offering new insights and actionable examples for the field. This dissertation not only bridges the identified research gap but also establishes a foundation for further exploration of the full potential of concurrency in data-driven and AI applications and architectures, aiming at fulfilling the evolving performance demands of modern and future computing systems.
Show less

Title: Measurement and Control of Beam Energy at the Fermilab 400 MeV Transfer Line
Creator: Mwaniki, Matilda W.
Date: 2023
Description: Linac is the first machine in the Accelerator chain at Fermilab where particles are accelerated from 35 keV to 400 MeV and travel to the...
Show moreLinac is the first machine in the Accelerator chain at Fermilab where particles are accelerated from 35 keV to 400 MeV and travel to the Booster where they are stripped of the extra electrons to become protons. Tuning Linac is performed using diagnostics to ensure stable intensity and energy while minimizing uncontrolled particle loss. I have been revisiting diagnostics in the Linac in order to understand their signals and to ensure their data is reliable. I revisited Beam Loss Monitors (BLMs) for the loss data confidence. For the confidence of energy data there were two approaches. The first approach was time-of-flight measurements using Beam Position Monitors (BPMs) and beam velocity stripline pick-up that provides beam phase data. The second approach used the relation between beam position data from BPMs and dispersion values from MAD-X simulation to calculate energy. Our goal after understanding the data from the Linac diagnostics and finding the data reliable is to control the Linac parameters using Machine Learning techniques to increase the reliability and quality of beam delivered from Linac.
Show less

Title: Ultrasound Image Guided Robot Arm for Targeted Delivery of Therapeutic Drugs and MicroRNA for Cancer Therapy
Creator: Nagarajan Parimala, Abishek
Date: 2024
Description: Molecular imaging has revolutionized medical diagnostics by providing detailed insights into biological processes at the molecular level...
Show moreMolecular imaging has revolutionized medical diagnostics by providing detailed insights into biological processes at the molecular level within the living subject. Ultrasound Molecular Imaging (USMI) has emerged as a promising diagnostic imaging modality by utilizing targeted contrast agents to unveil crucial molecular information, including vascular biomarkers associated with cancer and other diseases. Despite its potential, the transition of Ultrasound Contrast Agents (UCA) from preclinical evaluation to FDA-approved clinical use faces challenges due to the short in vivo half-life of Micro-Bubbles (MBs), necessitating repeated administrations for comprehensive assessments. Moreover, conventional ultrasound imaging methods suffer from limited scanning areas and single-target focus, leading to low throughput in preclinical evaluations.This thesis addresses these challenges by proposing a robot-assisted whole-body scanning pipeline for preclinical evaluations in Ultrasound Molecular Imaging. By integrating a robotic arm into the imaging setup, this approach enhances scanning flexibility and precision, enabling scans across the entire body of a mouse. This extension of the imaging time window allows for comprehensive assessments without the need for repeated contrast agent administrations. Additionally, the ability to simultaneously scan multiple targets within the same session significantly increases the throughput of preclinical assessments, thereby improving the efficiency and reliability of Ultrasound Molecular Imaging in clinical translation.
Show less

Title: Evaluation of the Native Microbiota and Comparative Analysis of a Known Cronobacter Sakazakii and a Newly Isolated Bacillus Cereus Strain in Powdered Infant Formula
Creator: Patil, Sonali Prashant
Date: 2024
Description: There have been numerous reports of Powdered Infant Formula (PIF) recalls and outbreaks due to the absence of a kill step in the post...
Show moreThere have been numerous reports of Powdered Infant Formula (PIF) recalls and outbreaks due to the absence of a kill step in the post-pasteurization processing, improper handling pre and post processing and/or reconstitution, and lack of effective sanitization and cleaning of the food contact surfaces in the manufacturing facilities. The objectives of this present study were to 1) survey and identify background microflora in commercial PIF products through microbiological analysis, 16S rRNA, and whole genome sequencing (WGS); 2) compare the survival rate of a known Cronobacter sakazakii and a newly isolated Bacillus cereus DFPST-SP1 in PIF under a humidity level of 33 ± 3% over a period of 28 d; 3) examine the relative resistance of these two strains to thermal treatments at temperatures 40, 70, and 100 °C followed by storage at room temperature (RT) for 30 min; and 4) evaluate the bactericidal effect of 70% ethanol on the two artificially deposited bacterial strains on stainless steel (SS) and plastic coupons. Three biological trials were conducted for each study. To determine whether the increase, decrease, or difference in the bacterial populations and other parameters like water activity (aw) was statistically significant, a T-test was performed (p ≤ 0.05 was considered significant). Results of 16S rRNA sequencing revealed the presence of certain bacterial species in PIF, such as Lactococcus lactis, B. cereus, Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica, etc. distributed across a relative abundance of >25%, <25%, and ≤3%. After the enrichment and isolation as per Bacteriological Analytical Manual (BAM), C. sakazakii or S. enterica were not detected, while colonies exhibiting a blue-green appearance resembling Listeria spp. and certain Bacillus spp. were subjected to WGS for species-level identification. The assembly_1 from formulation 1 was confirmed as B. cereus sequence type 2255 and was renamed as B. cereus DFPST-SP1 in the contribution of this thesis work. The storage study conducted on PIF inoculated with C. sakazakii and B. cereus DFPST-SP1 at 33% RH showed that there was 0.25-0.27 log CFU/g reduction towards the end of 28 d, but no significant difference was observed between the two strains. The thermal challenge study revealed that the newly isolated B. cereus strain and C. sakazakii used in this study were highly thermotolerant. Based on the sanitizer challenge study, 70% ethanol was significantly more effective in reducing populations of C. sakazakii as compared to B. cereus. Moreover, higher log reductions of C. sakazakii 587 populations on stainless steel coupons compared to plastic coupons were observed, indicating that bacteria adhere more tightly to plastic surfaces than stainless steel (SS). Overall, the findings of this study shed new light on bolstering the safety standards of PIF and highlight the need for improved cleaning and sanitization procedures within manufacturing facilities in order to ensure the safety of reconstituted PIF, thereby enhancing public health, particularly infants and neonates.
Show less

Title: Three Essays on the Internet Economy
Creator: Sun, Yidan
Date: 2024
Description: In an era of digital platforms, the integrity and visibility of consumer reviews, the dynamics of digital advertising markets, and the role of...
Show moreIn an era of digital platforms, the integrity and visibility of consumer reviews, the dynamics of digital advertising markets, and the role of software development kits (SDKs) emerge as pivotal elements shaping user experiences and platform economics. My research spans three distinct but interconnected domains: the impact of safety reviews on Airbnb, the effects of privacy protections on digital advertising markets, and the significance of SDK releases in the evolution of Apple's iOS app market. We find that critical reviews concerning the safety of an Airbnb listing's vicinity influence guest bookings negatively and, therefore, could boost platform revenues if such reviews were obscured, highlighting a misalignment between consumer interests and platform revenue objectives. This effect is more pronounced in low-income and minority neighborhoods, suggesting a nuanced impact on different community segments. In the digital advertising sector, we identify that data frictions disproportionately harm small publishers, especially when associated with smaller ad intermediaries, underscoring the vulnerability of niche players to market and regulatory changes. Lastly, our analysis of the iOS app market reveals the instrumental role of SDK releases in fostering the app ecosystem's growth, independent of the expanding iPhone user base. Together, these findings underscore the complex interplay between consumer feedback, technological advancements, and market dynamics in digital environments, urging a balanced approach that safeguards consumer interests while fostering innovation and equitable market practices.
Show less

Title: An Alternative Approach for the Jefferson Lab Electron-Ion Collider Ion Accelerator Complex
Creator: Martinez Marin, Jose Luis
Date: 2020
Description: An assessment by the National Academy of Sciences (NAS) of the scientific merit for a future Electron Ion Collider (EIC) in the US concluded...
Show moreAn assessment by the National Academy of Sciences (NAS) of the scientific merit for a future Electron Ion Collider (EIC) in the US concluded that such a facility would be unique in the world and enable indispensable research on current and compelling scientific questions. This assessment confirmed the recommendations of the 2015 Nuclear Science Advisory Committee (NSAC) for an EIC with highly polarized beams of electrons and ions, sufficient luminosity and sufficient, variable center-of-mass energy. Proposals were requested for a cost-effective design that uses existing accelerator infrastructure to reduce the risk; one of two major proposals submitted for consideration originated from the Thomas Jefferson National Accelerator Facility (JLab). The Jefferson Laboratory Electron-Ion Collider (JLEIC) would use the Continuous Electron Beam Accelerator Facility (CEBAF) at JLab as a full-energy electron injector. The primary accelerator challenges are twofold: producing and maintaining a high degree of polarization for both beams, and achieving high luminosity. This thesis project was part of an effort to produce an alternative, low-risk and cost- effective design for the JLEIC ion complex. The primary goal was not to find a replacement for the JLEIC ion complex design, but rather to investigate alternative options for the different components of the ion complex that could lower the overall cost, reduce its footprint, mitigate risk, and identify possible staging or future upgrades of the project. The platform for this thesis was the alternative design for the JLEIC ion complex that included (1) a more compact ion linac, (2) two staged ion boosters instead of one before injection to the collider ring, with a more compact and lower energy Pre-Booster ring as the first stage, and (3) the dual use of the electron storage ring (e-ring) as a second stage ion Large Booster.The alternative design was first investigated for medium energy (65-GeV center-of-mass), and was then upgraded following the National Academy of Sciences (NAS) review to higher energy (100-GeV center-of-mass). Developing a more cost-effective design and meeting all the requirements is challenging due to several constraints imposed on the alternative approach -- for example, the use of only room-temperature magnets for both ion boosters. There are also space limitations, the need to keep the shape and crossing angle of the ion Large Booster the same as the collider ring, ensuring reasonable length and aperture requirements for the magnets, and avoiding transition crossing for all the rings, which can cause beam dilution and instabilities.Development of both the Medium-Energy and the High-Energy options is presented. The Medium-Energy option consists of a 135 MeV injector linac, a 3 GeV octagonally-shaped Pre-Booster ring and a 11 GeV Large Booster. The High-Energy option consists of a 150 MeV (~ 40 MeV/u for Pb) injector linac, a 8 GeV (~ 2.04 GeV/u for Pb) non figure-8 Pre-Booster ring and a 40 GeV proton (~ 16 GeV/u for Pb) Large Booster, which would also serve as the electron storage ring (e-ring). The figure-8 shape of the Large Booster helps to maintain high polarization. High luminosity is achieved following a strategy to have a high bunch repetition rate of the colliding beams, very short bunch lengths, and small transverse emittances; the main concern here is to provide a lattice that is consistent with these requirements. The main results reported are the lattice design optimization and consolidation, benchmarking of the beam optics with different codes such as ELEGANT, COSY-Infinity, MAD-X, TRACE-3D, and Zgoubi, and spin resonance simulation results. Spin dynamics studies were performed for the linac and the Pre-Booster, and mechanisms to preserve the polarization are proposed. Beam formation and non-linear effects such as chromaticity, space charge, and intra-beam scattering were also studied to gain understanding of how the alternative approach could affect the baseline beam formation scheme and to ensure that the beam requirements are met through the injector chain with this alternative approach. It was shown that the polarization can be preserved through the alternative ion complex even with the more compact linac and a Pre-Booster that does not have a figure-8 shape by using a sufficiently long spin correction solenoid in the linac and a partial Siberian snake in the Pre-Booster. The baseline beam formation scheme could still be used to reach the required beam characteristics for collider injection. Cooling is not needed in the more compact Pre-Booster, and the large, higher energy booster helps to avoid space charge effects at extraction. This study has confirmed the effectiveness of the alternative approach as concerns the optics, acceleration, polarization, and beam formation. The ion injectors are sufficiently compact, and the ion Large Booster size and shape are consistent with the e-ring requirements, enabling the desired dual functionality of that machine. This work created a basis for design discussions during the JLEIC design process. The final High-Energy design for the JLEIC ion complex adopted design features that came from the alternative design studies, which were derived in part from this work—in particular, the shorter, lower-energy linac, the use of two boosters in the injection chain before the collider ring, and the ability to have only room-temperature magnets in the boosters, with superconducting magnets used only in for the collider ring.
Show less

Title: FEARING FORGETTING? DEVELOPMENT OF A SCALE TO ASSESS ATTITUDES ABOUT DEMENTIA IN THE LAY POPULATION
Creator: Ogu, Precious N
Date: 2020
Description: Individuals with dementia show a progressive decline in cognitive functioning which results in an inability to complete activities of daily...
Show moreIndividuals with dementia show a progressive decline in cognitive functioning which results in an inability to complete activities of daily living (American Psychiatric Association, 2013). Early diagnosis of dementia is a positive prognostic indicator (World Alzheimer Report, 2011) and is widely regarded as an important pre-condition for improving dementia care (Kim et al., 2015; Vernooij-Dassen et al., 2005). However, negative attitudes and stigma towards dementia could possibly interfere with an individual’s willingness to recognize or accept the idea of themselves having the disease through label avoidance. The goal of the present study was to contribute to understanding the perception of dementia by developing a quantitatively derived and psychometrically validated measure that encompasses the positive and negative attitudes towards dementia held by people without dementia. This study also explored the potential association between negative attitudes about dementia and lack of familiarity with dementia as familiarity with individuals with mental illness is related to stigmatizing attitudes towards mental illness. These goals were achieved by a principal components analysis (PCA) of 56 modified items from extant and well-validated mental illness attitude scales (Community Attitudes to Mental Illness, CAMI, Taylor & Dear, 1981; Social Distance Scale, SDS, Link, 1986; Depression Stigma Scale, DSS, Griffiths et al., 2004). Convergent validity was assessed by examining the relationship between the final derived measure and a construct associated with negative attitudes about mental illness (Mental Retardation Attitude Inventory-Revised, MRAI-R). Discriminant validity was assessed by examining the relationship between the final measure and a construct that should be unrelated to negative attitudes about mental illness (Belief in a Just World Scale, BJW). Finally, exploratory analyses were conducted to assess if attitudes measured by the newly created scale are related to participants’ familiarity with dementia (Level of Familiarity Scale, LoFS, Corrigan et al., 2001). 400 adults with no history of dementia were recruited through Amazon’s MTurk. Participants were compensated by a credit to their Amazon account upon completion of the survey. The PCA supported 2 conceptually different (not method variance) latent components titled Negative Attitudes and Positive Attitudes. These 2 components comprise the Attitudes to Dementia Inventory (ADI). Construct validity was partially supported for each component of the ADI. Degree of familiarity with dementia was not associated with negative or positive attitudes about dementia. Overall, this study is an important contribution to dementia attitudes research. Given the identification of Negative Attitudes and Positive Attitudes have been identified as distinct dimensions of dementia attitudes, the ADI can be used to further investigate how negative reactions towards dementia might cause delays in initiating medical intervention and treatment, and also to examine whether positive attitudes provide any protections against the probable effects of negative attitudes on stigma and help-seeking behaviors. Since the early recognition and diagnosis of dementia is widely regarded as an important condition for improving dementia care (Kim et al., 2015; Vernooij-Dassen, et al., 2005), the ADI can be used to inform stigma-prevention, which hopefully translates into improved help-seeking behaviors.
Show less

Title: GROWTH KINETICS OF SALMONELLA ENTERICA DURING REHYDRATION OF DEHYDRATED PLANT FOODS AND SUBSEQUENT STORAGE
Creator: Ren, Yuying
Date: 2020
Description: Dehydrated plant foods have low water activities and do not support the growth of pathogenic bacteria like Salmonella enterica. Once...
Show moreDehydrated plant foods have low water activities and do not support the growth of pathogenic bacteria like Salmonella enterica. Once rehydration, the water activities will increase to > 0.92, and along with their neutral pHs, plant foods may be able to support the growth of S. enterica. Therefore, product assessments are required to determine the extent to which these products support growth of S. enterica. The purpose of this study was to determine the growth kinetics of S. enterica during rehydration with 5 or 25 °C water, and subsequent storage of dehydrated potatoes, carrots, and onions at 5, 10, and 25 °C. Fresh plant foods were dehydrated at 60°C (140°F) for 24 h. Dehydrated plant foods were inoculated with 4 log CFU/g of a 4-strain cocktail of S. enterica and dried for 24 h. Samples were rehydrated using 4-volumes of 5 or 25 °C water for 24 h. During rehydration, 30 g of sample was removed and drained for 10 min. Ninety mL of BPB was added to triplicate 10-g samples. Serial dilutions of the homogenate were plated onto TSA overlaid with XLD agar for enumeration of S. enterica. After 24 h rehydration, the remaining samples were drained and stored in containers at 5, 10, and 25°C for 7 d. S. enterica was enumerated at 1, 3, 5, and 7 d. Three independent trials were conducted. Growth kinetics were determined using DMFit and data were statistically analyzed using Student’s t-test (α=0.05). Overall, the growth rates of S. enterica when 5 °C water was used for rehydration were higher than when 25 °C water was used for potatoes and carrots. The highest growth rate of S. enterica was 3.74 log CFU/g per d on potatoes, leading to a 1 log CFU/g increase in S. enterica after only 0.27 d (16 h) which occurred during storage at 25 ℃ after 5℃ water rehydration. The highest growth rate on carrots was 1.98 log CFU/g per d (requiring only 0.51 d to increase 1 log CFU/g) when rehydrated with 5℃ water and stored at 25 ℃. The growth rates were the lowest during the storage of rehydrated onions. S. enterica required 12.5 d to increase 1 log CFU/g (the growth rate was 0.61 log CFU/g per d) when the onions were rehydrated with 25 ℃ water and stored at 25 ℃. The results of this study determined that S. enterica could survive and grow in dehydrated plant foods during rehydration and storage, highlighting the need for product assessments for these types of foods.
Show less

Title: Targeting Respiratory Pathways to Combat Persistence: Investigating the Role of Respiratory Complexes in Klebsiella Aerogenes Persister Cell Formation
Creator: Barnes, Alyssa Britney
Date: 2024
Description: Klebsiella aerogenes is a multidrug-resistant nosocomial pathogen that poses significant challenges due to its ability to form persister cells...
Show moreKlebsiella aerogenes is a multidrug-resistant nosocomial pathogen that poses significant challenges due to its ability to form persister cells that evade antibiotic treatment and contribute to chronic infections. This study explored the relationship between respiratory complexes and persister cell formation, focusing on NDH-2, NQR, and cytochrome oxidases. The research used a combination of wild-type and mutant strains, along with respiratory inhibitors and antibiotics, to identify key metabolic pathways influencing persister survival.The results revealed that NDH-2 plays a pivotal role in persister cell formation, with NDH-2 mutants demonstrating a significant reduction in persister populations over time. Comparative analysis of respiratory mutants highlighted differential reliance on oxidative phosphorylation, with NDH-2 being essential for maintaining energy metabolism during stress. In contrast, mutants lacking NQR or nuo complexes exhibited slower colony count declines, suggesting a shift to low-energy states that mimic persister characteristics. These findings emphasize the critical role of the respiratory chain, particularly NDH-2, in bacterial persistence and highlight its potential as a therapeutic target. By disrupting energy metabolism, it may be possible to eradicate persister cells and reduce the recurrence of infections caused by K. aerogenes, providing a promising avenue for combating multidrug-resistant pathogens.
Show less

Title: Optimal Power Allocation Over Gaussian Broadcast Channels
Creator: Chen, Pengpeng
Date: 2024
Description: For Gaussian broadcast channel, the maximal capacity region can be achieved. A power assignment over Gaussian broadcast channels splits the...
Show moreFor Gaussian broadcast channel, the maximal capacity region can be achieved. A power assignment over Gaussian broadcast channels splits the power budget at the access point among all user channel pairs subject to per-channel upper bounds on the sum power, and is optimal if it maximizes the weighted sum-rate (WSR). The capacity region reaches its maximum when the weighted sum rate over Gaussian broadcast channels is maximum, making this a classic and significant problem within the wireless communication community.This thesis begins by addressing the problem of maximizing the WSR. In the single Gaussian broadcast channel, the traditional methods for computing optimal power assignment have utilized Lagrange multipliers for convex optimizations, with computational complexities ranging from $O(|U|^3)$ to $O(|U|^2 \log(|U|))$. A more recent approach has reduced this to $O(|U|^2)$. We propose a new geometric algorithm for optimal power assignment over a single Gaussian broadcast channel. This algorithm operates with linear complexity, provided all users are pre-sorted by weight or noise. Our method offers an intuitive water-filling interpretation, which subsequently allows us to develop a water-filling algorithm for optimal power assignment over parallel Gaussian broadcast channels. The complexity of this algorithm remains linear in terms of the number of user-channel pairs, assuming pre-sorted users by weight. For computing an optimal power assignment over parallel Gaussian broadcast channels, no explicit time complexity is known in the literature. Due to power constraints imposed by the base station, energy efficiency is an essential metric to evaluate the performance of these transmissions. Following the WSR optimization, we then tackle the problem of maximizing the weighted energy efficiency (WEE). In this context, a power assignment over parallel Gaussian broadcast channels involves splitting a power budget at the access point among all channel-user pairs, subject to per-channel upper bounds on the sum power. This allocation yields specific rate allocations to each channel-user pair. The WEE is defined as the ratio of the weighted sum rate to the sum-power plus a fixed positive overhead. The Max-WEE problem seeks a power assignment that maximizes the WEE. Although special variants of Max-WEE, such as those with unit weights or two users per channel, have been extensively studied, existing algorithms for these variants lack known bounds on running time. This is primarily because they rely on general-purpose methods for fractional programming.In this thesis, we derive fundamental properties and closed-form expressions for the maximum WEE. Building on these theoretical foundations, we devise a simple yet effective water-filling algorithm for solving the Max-WEE problem. Our algorithm, under the assumption that all users are pre-sorted by weight, has the linear complexity in terms of the number of channel-user pairs. Furthermore, under a mild pre-sorting condition, we develop an additional linear-complexity algorithm for the Max-WEE problem, subject to rate demand constraints.Overall, our research presents novel and efficient algorithms for power assignment over Gaussian broadcast channels, including the algorithms for maximizing the WSR, and the algorithms for maximizing the WEE. These algorithms demonstrates significant potential for practical applications in wireless communication systems. Our work offers a comprehensive solution to fundamental problems in the field and paves the way for further advancements in wireless communications.
Show less

Title: Effect of Stress Triaxiality and Lode Angle on Ductile Fracture
Creator: Nia, Mahan
Date: 2023
Description: Although many ductile damage accumulation studies have been done in recent years, there is still insufficient research towards the development...
Show moreAlthough many ductile damage accumulation studies have been done in recent years, there is still insufficient research towards the development of ductile fracture models, mainly due to the difficulty of performing experiments under different states of multiaxial stress. The goals of this Ph.D. research are to (i) produce much-needed experimental data, (ii) investigate the performance of existing models against these data, and (iii) develop a new predictive ductile fracture model validated by experiments. The new model seeks to predict the fracture strain as a function of the stress triaxiality and normalized Lode angle. One of the prominent works in this area was done by Bai and Wierzbicki in 2008 by testing 2024-T351 aluminum alloy. They proposed an asymmetric 3D empirical fracture model with six model parameters. Thus, the Bai method was investigated alongside a new model for predicting ductile fracture. For that purpose, 2139-T8 aluminum alloy was chosen for our experimental program to evaluate these models better, and the data extracted from Bai's work was also used as an additional data set. An extensive experimental program was considered to create different stress states in the material, including tensile tests (with round smooth and four round notched and plate specimens), torsion, compression (with four smooth and two notched specimens), and shear-compression experiments (two different sizes). The specimens were longitudinally machined from a block of 2139-T8 aluminum alloy. The combined effects of two variables, stress triaxiality and normalized Lode angle, define a 3D fracture envelope for fracture strain. A parallel FE simulation (fine-tuned by the experimental results) has been performed for each experiment to evaluate the evolution of stress triaxiality and Lode angle in the gauge section of the specimens with complicated geometries. Finally, these results were used in developing two predictive fracture models. The first model is based on the Bai-Wierzbicki form of fracture. The second one is a new model that has been presented in this research. This new model is a modification of the Johnson-Cook fracture model and considers the simultaneous effects of Lode angle and stress triaxiality in fracture. The original Johnson-Cook fracture model (1984) does not consider the Lode angle effect. In the end, errors in the proposed approach to modeling ductile fracture have been compared to errors from Bai's work, resulting in the conclusions and recommendations for future studies.
Show less

repository.iit

Search the repository

Pages

Pages