Search results

Title: STRUCTURE-PROPERTY RELATIONSHIPS IN ANION EXCHANGE MEMBRANES FOR ELECTROCHEMICAL ENERGY CONVERSION AND STORAGE
Creator: Arges, Christopher George
Date: 2013, 2013-12
Description: Polymer electrolyte membrane (PEM) fuel cells are promising candidates for powering automotive vehicles, but their advancement has been...
Show morePolymer electrolyte membrane (PEM) fuel cells are promising candidates for powering automotive vehicles, but their advancement has been hindered by the costs associated with their platinum-based electrocatalysts. One strategy to resolve this problem is to replace the conventional acidic PEM with an alkaline anion exchange membrane (AEM) because fuel cells operated in alkaline media do not require platinum group metal catalysts. A significant challenge to realizing this concept is to design and implement an AEM that is chemically robust under alkaline conditions and that facilitates high ionic conductivity. This dissertation presents a scientific approach to address the aforementioned problems through investigation of alternative cations, beyond quaternary trimethylammonium, to understand what chemical features influence ion conductivity and alkaline stability. It was postulated that selecting cations with larger free base conjugate pKA values (i.e., greater basicity) would yield improved AEM alkaline stability and ionic conductivity. The pKA value accounts for the steric hindrance, inductive, and resonance features of an organic cation and these features influence a cation’s interaction with hydroxide. Udel® polysulfone (PSF) and poly(2,6-dimethyl 1,4-phenylene) oxide (PPO) were selected as the model polymer backbones because they can be tailored with different cation groups. The types of cations assessed were of the quaternary ammonium and phosphonium types and 1-methylimidazolium. The prepared AEMs demonstrated a direct correlation between the cation’s free base conjugate pKA and anion conductivity for most cations assessed. Alkaline stability was assessed through multi-dimensional NMR to determine the degradation products in AEMs. NMR confirmed that the cation groups x xxii degraded through fundamentally different degradation mechanisms dependent upon their chemical make-up. Because the degradation mechanisms were different, the rate of degradation of the cation groups did not demonstrate a correlation to the cation’s free base conjugate pKA. If the cations did proceed through the same degradation mechanism, then a correlation was observed. Additionally, it was discovered that the cation groups in PSF and PPO triggered polymer backbone degradation in alkaline despite the resiliency of both these pristine polymers in alkaline solutions. The AEMs prepared were successfully demonstrated in several electrochemical energy storage and conversion technologies (including alkaline fuel cell, alkaline water electrolyzer, and the all-vanadium redox flow battery).
PH.D in Chemical Engineering, December 2013
Show less

Title: SECURE DATA SERVICE OUTSOURCING IN CLOUD COMPUTING
Creator: Wang, Cong
Date: 2012-04-22, 2012-07
Description: Cloud computing economically enables a fundamental paradigm of data service outsourcing, which provides lower up-front capital costs and less...
Show moreCloud computing economically enables a fundamental paradigm of data service outsourcing, which provides lower up-front capital costs and less hands-on management. However, outsourcing data services to the commercial public cloud deprives customers' control over the systems that manage their data, raising security and privacy as the primary obstacles to the adoption of the cloud. To address these challenges, in this dissertation we explore the problem of secure and privacy-assured data service outsourcing in cloud computing. We aim at deploying the most fundamental data services including data storage, search, and sharing on the commercial public cloud, with built-in security and privacy assurance as well as high level service performance, usability, and scalability. Our contributions are as follows: Firstly, we focus on privacy-preserving secure cloud storage auditing to maintain strong storage correctness guarantee, given the di culty that data les are no longer locally possessed by data owners. We rst develop a random-masking sampling approach to allow a third party auditor to perform on-demand privacy-preserving storage correctness auditing on behalf of data owners, without violating owners' data privacy. For storage correctness assurance with data dynamics, we further investigate a novel sequence-enforced Merkle Hash Tree and manipulate it with the random sampling approach to support fully dynamic data operations. Secondly, we focus on privacy-assured and e ective cloud data search services with strong privacy-assurance, while enjoying high service-level performance inherently demanded by the large number of data users and huge amount data les. We rst investigate a widely applicable fuzzy/similarity keyword search problem, and develop a brand new symbol-based trie-traverse searching approach, where transformed fuzzy keywords extracted from data les are stored using a multi-way tree structure, while protecting keyword privacy. To enable search result relevance ranking, we further investigate secure ranked search, which facilitates e cient server-side result ranking without leaking any keyword related information. Thirdly, we study how to enable scalable and owner-controlled cloud data sharing services, given the challenge that data no longer resides on owners' trusted domain. We rst associate data with a set of meaningful attributes, use logical composition of attributes to re ect ne-grained data access, and enforce owner's control via attribute-based encryption. For the inherent scalability requirement of cloud system, we further leverage the cloud as a mediated proxy, to which data owners can delegate most cumbersome data/user management workload, without a ecting the underlying data con dentiality.
Ph.D. in Electrical Engineering, July 2012
Show less

Title: ANALYSIS OF ZENO STABILITY IN HYBRID SYSTEMS USING SUM-OF-SQUARES PROGRAMMING
Creator: Murti, Chaitanya
Date: 2012-12-14, 2012-12
Description: Hybrid dynamical systems are systems that combine continuous dynamics with discrete transitions. Such systems can exhibit many unique...
Show moreHybrid dynamical systems are systems that combine continuous dynamics with discrete transitions. Such systems can exhibit many unique phenomena, such as Zeno behavior. Zeno behavior is the occurrence of infinite discrete transitions in finite time. This phenomenon has been likened to a form of finite-time asymptotic stability, wherein trajectories converge asymptotically to compact sets in finite time whilst undergoing infinite transitions. Corresponding Lyapunov theorems have been developed. The main objective of our research was to develop computational techniques to determine whether or not a given hybrid system exhibits this Zeno phenomenon. In this thesis, we propose a method to algorithmically construct Lyapunov functions to prove Zeno stability of compact sets in hybrid systems. We use sum-of-squares programming to construct Lyapunov functions that allow us to prove Zeno stability of compact sets for hybrid systems with polynomial vector fields. Examples illustrating the use of the proposed technique are also provided. Finally, we provide a method using sum-of-squares programming to show Zeno stability of compact sets for systems with parametric uncertainties in the vector field, guard sets and domains, and transition maps. We then discuss potential applications of the proposed methods, along with examples.
M.S. in Electrical Engineering, December 2012
Show less

Title: EXECUTIVE FUNCTION AND DEPRESSIVE SYMPTOMS IN PATIENTS WITH ISCHEMIC STROKE
Creator: Marola, Jennifer
Date: 2013, 2013-07
Description: Previous research has demonstrated impairment following stroke, including depressive symptoms (Herrmann et al., 2011; O'Brien et al., 2003;...
Show morePrevious research has demonstrated impairment following stroke, including depressive symptoms (Herrmann et al., 2011; O'Brien et al., 2003; Robinson, 2006; Robinson & Spalletta, 2010; Teper & O'Brien, 2008) and cognitive impairment, particularly in executive function (Canning, Leach, Stuss, Ngo, & Black, 2004; Carew, Lamar, Cloud, Grossman, & Libon, 1997; Garrett et al., 2004; Kertesz & Clydesdale, 1994; Lafosse et al., 1997; Madureira, Guerreiro, & Ferro, 2001; Padovani et al., 1995; Su, Lin, Kwan, & Guo, 2008). Current research is limited by the use of primarily patients in the hospital with multiple types of stroke and physical impairment. Additionally, a conceptualization of executive function by Stuss and colleagues (Stuss, Shallice, Alexander, & Picton, 1995) has not been thoroughly investigated utilizing factor analytic techniques. The current study attempted to expand research on executive function and depressive symptoms in individuals with ischemic stroke. This study examined performance on measures of executive function, memory, language, and visuospatial ability, along with measurement of depressive symptoms in participants with ischemic stroke and healthy matched control participants. Results revealed that participants with stroke performed significantly worse in all cognitive domains than control participants. More specifically, in participants with stroke, executive function was more impaired than memory, language, and visuospatial ability. A regression analysis did not find that depressive symptoms accounted for additional variance in executive function above x demographic factors. Two and three factor models of executive function were not supported; the data more closely resembled a one factor model of executive function.
PH.D in Psychology, July 2013
Show less

Title: A STRUCTURAL ANALYSIS FRAMEWORK FOR CONCRETE FACED ROCKFILL DAMS
Creator: Quiroz, Juan E.
Date: 2013, 2013-12
Description: Concrete Faced Rockfill Dams (CFRD’s) are commonly built around the world. As energy demands soar and construction methods evolve, the...
Show moreConcrete Faced Rockfill Dams (CFRD’s) are commonly built around the world. As energy demands soar and construction methods evolve, the interest for construction of CFRD’s with larger heights has increased tremendously. However, because of construction of higher CFRD’s, some dams have experienced considerable fractures at the concrete faces. Well known cases include Campos Novos (Brazil), Barra Grande (Brazil), and Mohale (South Africa), where in some instances these cracks have led to dewatering of the reservoir to allow for the concrete slabs repairs. The development of these fractures may be attributed to the highly deformable rockfill body. In general, the state-of-the-art design of CFRD’s is mostly based on common practice rather than rigorous analysis procedures. And as such, cracking problems because of deformability of the rockfill may not be properly predicted unless a detailed analysis is performed. In this work, a new framework for analysis of CFRD’s is developed that is capable of predicting the possible concrete-facing failure. As a part of this framework, a comprehensive non-linear finite element analysis (FEA) scheme is developed to model the construction sequence, the contact interaction between the concrete facing and the rockfill body, and the impounding of the reservoir. As a case study, using the developed framework, the Kárahnjúkar CFRD (Iceland, 198m height) is analyzed, the results are validated by the field measurements, and mitigation measures suggestions are provided. This methodology, based on the results of the investigation, provides guidelines and establishes a framework for analysis of CFRD’s that can be used for design purposes.. Keywords: CFRD, Concrete Faced, Rockfill, Dam, Finite Element Analysis.
PH.D in Structural Engineering, December 2013
Show less

Title: A BAYESIAN UPDATING APPROACH IN STRUCTURAL HEALTH MONITORING FOR DAMAGE DETECTION AND ASSESSMENT
Creator: Dirbaz, Mojtaba
Date: 2013, 2013-05
Description: The primary goal of Bridge Condition Assessment (BCA) is to determine the condition of a bridge to prevent any catastrophic failure as well as...
Show moreThe primary goal of Bridge Condition Assessment (BCA) is to determine the condition of a bridge to prevent any catastrophic failure as well as to enhance the structure’s safety and serviceability. The structural health and condition of in-service bridges is generally assessed through visual inspections and nondestructive testing and evaluation (NDT/NDE) methods conducted on a pre-set schedule. However, the ratings obtained from current visual inspections on a bridge are subjective, and do not include the uncertainty inherent in the results. Moreover, the condition ratings are often based on independent inspections and do not take into account the dependence of results on previous conditions of a bridge and prior condition ratings compiled for it. Furthermore, there is also a certain level of uncertainty involved in relating subjective ratings to the actual condition of the bridge. This study is aimed at conducting a research on damage detection of existing bridges utilizing available information on their structural conditions. The first part of the research focuses on a new method for assessing the condition of a bridge based on subjective ratings obtained for the bridge. This method will hereafter be referred to as Bayesian Bridge Condition Assessment (BBCA). BBCA consists of three parts: (1) identification of condition states for structural components, (2) determination of a Damage Index (DI), a parameter to describe the extent of damage to a structural component, and (3) determination of an Updated Damage Index (UDI) using Bayesian updating approach. UDI offers an enhanced measure that incorporates not only the relation between subjective rating and the structure’s health condition, but also the significance of new information as it becomes available. The basic assumptions and x general formulations of the Bayesian updating method is presented. Numerical illustrations are provided to demonstrate the applicability of the method to highway bridges. It is shown that the method described in this study is especially applicable to bridges for which visual inspection data are compiled on a periodic basis. One of the methodologies for damage detection and assessment is to use sensor data for identifying the modal characteristics of the structure. The second part of this research focuses on improving upon damage detection methods using sensor and/or modal data. Thus a new method for damage detection and assessment of structures using finite element analysis, and modal data is developed and demonstrated. This method will hereafter be referred to as Bayesian Structural Condition Assessment (BSCA). Using this method, (1) a Finite Element (FE) design model of the structure (undamaged) is constructed; (2) the measured modal data is updated using a Bayesian framework; and (3) the FE model of existing structure (with possibility of damage) is obtained using updated modal data based on an iterative optimization method that is used in estimating the stiffness of the damaged structure. Using these steps, the location and extent of any possible damage is then determined based on the difference between a structural element stiffness for the “as built condition” and “damaged condition.” Several numerical illustrations are presented to demonstrate the capability of the method to detect the location and extent of the damage. This method has been applied to a structural health monitoring benchmark problem; and it has been shown that it can identify the location and extent of damage with more accuracy than most other existing models. Keywords: Bayesian Updating, Condition Assessment of Structures, Modal Data, Visual Inspections, Finite Element Model, Bridges
PH.D in Structural Engineering, May 2013
Show less

Title: ASSESSMENT OF THE VALIDITY AND RELIABILITY OF THE ROMANTIC RELATIONAL INVENTORY: A MEASURE OF THE DEGREE OF ADAPTIVENENESS WITHIN THE DECLARATIVE ASPECTS OF ROMANTIC RELATIONAL SCHEMA
Creator: Grix, Bethany
Date: 2011-11-28, 2011-12
Description: A measure was developed to quantify an individual’s romantic relational schema, after conducting a literature review of the variables to which...
Show moreA measure was developed to quantify an individual’s romantic relational schema, after conducting a literature review of the variables to which it was related. The measure was designed to assess comprehensively the dimensions and degree of adaptiveness within this important construct. This new measure, the Romanic Relational Inventory (RRI), was subject to psychometric analyses and a final 93 item measure was derived from the factor analyses on 104 original items. The RRI was shown to be a reliable and valid measure of the descriptive components of romantic relational schema as demonstrated by the measures of external validity and reliability analyses. A series of Experimental Factor Analyses suggested that the initial single factor hypothesized domains were supported (i.e., Relationship Components; Expectations of Relationship Behaviors; Partner Components, which included two sub-domains: Partner Traits and the Congruence of Self with Other; and Global Perceptions of Romantic Relationships). The results suggest that the RRI may be a reliable and valid multidimensional measure, with distinct yet overlapping dimensions or sub-constructs.
M.S. in Psychology, December 2011
Show less

Title: NUTRIENT REMOVAL FROM SECONDARY EFFLUENTS USING REACTIVE FILTRATION
Creator: Bhupal, Gurmanpreet Singh
Date: 2015, 2015-07
Description: Simultaneous removal of dominant forms of nitrogen and phosphorous present in secondary effluents was studied with reactive filtration as the...
Show moreSimultaneous removal of dominant forms of nitrogen and phosphorous present in secondary effluents was studied with reactive filtration as the treatment method. The selected media for filter bed included Granular Ferric Hydroxide (GFH), Calcite (C), Silica Sand (S), and Activated Alumina (A). The focus was to evaluate the performances of media blends GFH-C-S and A-C-S for removal of sRP and sNO3-N in lab scale batch and column experiments using secondary effluents provided by Calumet Water Reclamation Plant. The media blends performed better for sRP removal than sNO3-N removal with A-C-S being outperformed by GFH-C-S in batch experiments, and hence was not used for column experiments. The removal kinetic study using GFH-C-S showed 100% sRP removal rate and 45% NO3-N removal rate for an optimal contact time of 2 minutes, with latter showing gradual desorption after initial instant adsorption. The optimal adsorbent dosage for sRP was found to be 15g (1:1:1) whereas for NO3-N, the removal rates increased with an increase in adsorbent dosage. Column experiments with GFH-C-S gave an adsorption capacity of 1.8 mg/g for an equilibrium concentration of 0.1 mg P/L with breakthrough occurring after a throughput of 603 bed volumes.
M.S. in Environmental Engineering, July 2015
Show less

Title: SOLIDS ROLE IN TERTIARY CHEMICAL PHOSPHORUS REMOVAL BY ALUM
Creator: Maher, Chris
Date: 2013, 2013-12
Description: Chemical phosphorus (P) removal is commonly implemented in wastewater treatment to remove P to very low levels (
Show moreChemical phosphorus (P) removal is commonly implemented in wastewater treatment to remove P to very low levels (<0.1 mg P/L). The dose of precipitant (Al or Fe) needed is several times the stoichiometric dose in order to achieve a filtered effluent level of < 30 μg TP/L. The mechanistic basis for P removal using chemical precipitant addition is generally considered to be more than simple precipitation. The role of adsorption and/or complexation in removal of reactive or unreactive phosphorus to the already formed chemical precipitates or complexes has been investigated. Potential operational efficiency gains resulting from age of chemically precipitated solids and the recycle of these solids to the process stream was undertaken at the Iowa Hill Water Reclamation Facility which employs the DensaDeg® process (IDI, Richmond, VA) for tertiary chemical P removal. The effect of solids age was found to be insignificant over the solids retention time of 2 to 8 days, indicating that the solids were unaffected by the aging effects of decreasing porosity and surface acidity, and that the bulk of solids were retained in the clarifier blanket, hence providing no advantage in the removal mechanisms from increased concentration of solids. When solids recycle was redirected from the traditional location of the flocculation reactor to a point just prior to chemical addition in the chemical mixing reactor, lower effluent soluble P concentrations at lower molar doses of aluminum were achieved. At laboratory scale, the “spent” or “waste” chemical sludge showed high capacity and rapid kinetics for P sorption from real wastewater effluents. A number of scenarios were tested and the wide range of parameter values indicate that the sorption reaction is rather specific to the sludge and the process water matrix. x Saturation concentrations were in the range of 8 to 29 mg soluble reactive P/g solids. Higher saturation concentrations were found at higher temperatures. Ambiguous results were obtained for the effect of sludge age on capacity, implying dependence on either aging conditions or sample matrices. In all instances alum sludge produced without a coagulant aid polymer had a much higher capacity for P sorption than polymer based sludge. The reaction reached equilibrium in less than 10 minutes with 50% or greater removal within the first minute. Removal reactions were modeled well by nth order equations with n 3 and by exponential data fitting. Modeled as a sorption process, the pseudo-second order model presented by Ho and McKay in 1999 proved to be an excellent fit. Second order rate constants ranged approximately from 0.1 to 6 (g mg-1 min-1) depending on the P fraction examined, age of sludge, reaction temperature, and presence or absence of coagulant aid polymer in the sludge.
M.S. in in Environmental Engineering, December 2013
Show less

Title: STUDY OF PARALLEL AUTOCATALYTIC REACTIONS IN COUPLED REACTORS
Creator: Hegishte, Swapnil R.
Date: 2012-04-29, 2012-05
Description: The inherent nonlinearity in cubic autocatalytic system has been the reason for its study in various combinations. Parallel cubic...
Show moreThe inherent nonlinearity in cubic autocatalytic system has been the reason for its study in various combinations. Parallel cubic autocatalytic reactions are analogous to the simultaneous consumption of multiple substrates by the same autocatalytic species. Steady state analysis reveals that there can be up to five steady states possible and two of them are always unstable. Individual parameter effect on steady state structure leads to identification of an isola, mushroom and other exotic patterns on equilibrium plot. Stability analysis leads to developing an operating diagram, which also explains the oscillatory behavior with the study of Hopf bifurcation. Concept of coupled isothermal continuous stirred tank reactors enriches the complexity of the system and the steady state behavior. The two reactors are identical in terms of the feed concentrations and the reactor space time. The coupled reactor system can have maximum twenty five steady states at very low interaction rate (R → 0), nine out of which may be stable. The steady state analysis portrays the patterns for transition in number of steady states as R is varied. Appearance of an additional Hopf point confirms the effect of complexity of coupled reactors configuration on stability structure of the system. Numerical simulations exhibit the rich steady state behavior in coupled reactors. Dynamic study for single reactor confirms the possibility of chaos in multistable parameter space. The coupled reactor dynamics focuses on the limit cycle interactions and emergence of chaos due to an added complexity.
M.S. in Chemical Engineering, May 2012
Show less

Title: REAL-TIME ARAIM USING GPS, GLONASS, AND GALILEO
Creator: Cassel, Ryan
Date: 2017, 2017-05
Description: Since the inception of GPS, satellite navigation has been a widely used means of navigation for both military and civilian users on the ground...
Show moreSince the inception of GPS, satellite navigation has been a widely used means of navigation for both military and civilian users on the ground and in the air. GPS is capable of providing highly accurate positioning and timing information to users around the globe. However, for certain applications, providing high-accuracy position estimates is not sufficient. Because satellites are susceptible to faults, the safety, or integrity, of the position estimates is also of concern, especially in civilian aviation where safety is critical. As such, receiver autonomous integrity monitoring (RAIM) can be used in order to detect and potentially exclude these faults and guarantee the safety of the position estimate. RAIM has been capable of supporting horizontal aircraft navigation using GPS for decades and has proven to be a useful tool. Now, as more global navigation satellite systems (GNSS) become available, the potential for advanced RAIM (ARAIM) to support vertical guidance for aircraft using multiple constellations has become an area of great interest. In this work, the ARAIM methodology is discussed, and the procedure is outlined, including protection level calculation, fault detection, and exclusion. The procedure is then implemented in a real-time ARAIM prototype. While GPS and Galileo aim to provide worldwide coverage for vertical guidance by 2020 when Galileo is fully operational, ARAIM performance can be examined at present using the current full-strength GPS and GLONASS constellations. This prototype performs position estimation and ARAIM using measurements from the current GPS, GLONASS, and partial Galileo constellations. ARAIM results in a variety of different GNSS scenarios are examined. Furthermore, this work investigates two methods of improving the computational efficiency of the ARAIM algorithm: satellite selection and fault mode grouping.
M.S. in Mechanical and Aerospace Engineering, May 2017
Show less

Title: STRUCTURE AND DYNAMICS OF MODIFIED NUCLEOSOMES UNDER EPIGENETIC REGULATION
Creator: Kohestani, Havva
Date: 2022
Description: Epigenetic regulations are critical in inducing heritable phenotype changes in biological systems without alternating their core genetic DNA...
Show moreEpigenetic regulations are critical in inducing heritable phenotype changes in biological systems without alternating their core genetic DNA sequences. In vivo, reversible epigenetic mechanisms engage various molecular structures from RNAs to larger proteins. The present thesis investigates the influence of epigenetic regulatory factors such as histone protein variants and small non-coding RNAs on the dynamics and structure of nucleosome core particles. Our results show that a histone substitution is an efficient tool in increasing or decreasing the exposure of DNA to post-translational modification (PTMs) factors or larger molecular assembly elements. Substitution of canonical H2A with H2A.B alters DNA-dimer interface resulting in increased breathing and accessibility of DNA. Replacement of canonical H3 with CENP-A variant impacts the overall core-DNA dynamics with flexibility of DNA entry/ exit sites and more rigid tetramer structure. Histone substitution also affects the micro to macro level molecular communication in the nucleosome system. The long-range correlated motions are weakened in H2A.B compared to canonical NCP. We observed a reduction in effective long-range DNA-DNA and DNA-core allosteric pathways in CENP-A NCP compared to canonical and Widom NCPs. Non-coding RNAs increase the tendency of the H3 tail histones to interact with DNA and induce the structural changes in the initial ideal B-DNA of NCP. Overall, the interaction of epigenetic regulatory factors in the form of protein or nucleic acids shifts the energetic and structural properties of the original nucleosome system. As a result, the chromatin structure is prepared to generate the proper biological response throughout spermatogenesis, chromosome segregation, or PTMs assembly.
Show less

Title: IDENTIFICATION OF THE RIBOFLAVIN BINDING SITE IN VIBRIO CHOLERAE ION PUMPING NQR COMPLEX
Creator: Lee, Chia-Hsing
Date: 2021
Description: NQR is a six-subunit complex that transfers electrons from NADH to ubiquinone, one of the essential enzymes in the bacterial respiratory chain...
Show moreNQR is a six-subunit complex that transfers electrons from NADH to ubiquinone, one of the essential enzymes in the bacterial respiratory chain of many pathogens such as Vibrio cholerae, Pseudomonas aeruginosa, Chlamydia trachomatis. Its electron transfer path requires three different flavin cofactors to facilitate: FAD, FMN, and riboflavin. The FMN in subunit B (FMNB) brings electrons to riboflavin and then transfers it to the final electron receptor UQ in subunit B, coupled with the Na+ pumping mechanism. NQR has a unique evolutionary history, and one of the pieces of evidence is that NQR has been reported as the only one flavoenzyme that uses riboflavin as its redox cofactor. However, the binding site of riboflavin has not been well understood. To gain insight into the electron transfer at this site in V.cholerae NQR, we generated mutants at the interface of subunits B, D, and E where the possible location of riboflavin is. To characterize these mutants, we assessed NQR properties with different approaches including enzyme kinetics and flavin radical profiling. We found that the mutagenesis surrounding the hydrophobic pocket disrupted the NQR activity, and cause the loss of neutral radical, but did not interfere with the binding affinity between the substrates and NQR. This study will help to understand electron transfer better in NQR and develop the drugs targeting the riboflavin binding site in the future.
Show less

Title: Stimulation-Responsive Materials for the Treatment of Disordered Tissues
Creator: Clutter II, Elwin Dean
Date: 2022
Description: Microenvironments offer physical and chemical cues to cells that affect their behavior. These cues can be bioactive chemicals such as drugs...
Show moreMicroenvironments offer physical and chemical cues to cells that affect their behavior. These cues can be bioactive chemicals such as drugs and cytokines, matrix cues like stiffness and composition, and electrical signals as seen in membrane potentials and epithelial wound healing. Controlling these cues can drive cell behavior toward apoptosis, proliferation, or changes in protein expression. In this thesis research, three components were used to model changes in cell behavior: the near infrared dye indocyanine green (ICG), silk fibroin (SF) from Bombyx mori silkworm cocoons, and carbon nanotubes (CNT). The mechanism of ICG photobleaching was studied for the efficacy to kill neuroblastoma cancer cells. ICG was twice as effective at killing neuroblastoma than fibroblast cells. Albumin stabilized monomeric ICG to enhance photobleaching by improving light interaction, and photodegradation of ICG into α,β-unsaturated aldehydes led to significant reduction of proliferation in neuroblastoma cells by targeting cell signaling components such as protein transcription factors. SF-ICG composite materials were developed into films and electrospun fibers. These composite materials were examined as light-activated wound coverings to control bleeding in hemorrhage, using ICG’s photothermal effect. ICG added an absorbance peak to SF at 805 nm. Irradiation decreased this peak, produced a new absorbance peak at 352 nm, and an increased fluorescence peak around 490 nm, showing photochemical changes that may be useful in sensor design. Increased heat production from irradiation of SF-ICG occurred in the films with 0.2% w/w ICG in SF during 1 min irradiation, whereas SF-ICG fibers required improvement of processing by ethanol vapor treatment (EVT) to reduce loss of ICG during preparation. EVT improved ICG retention in SF fibers during sterilization with 70% ethanol solution thus improving heat generation in the SF-ICG fibers. Heat evolved from SF-ICG 0.2% film solidified bovine blood within 42 s, with visible changes after the first 6 s. SF electrospun fibers were investigated to optimize silk preparation to reduce diameters and increase alignment to mimic local native cell environments with and without CNT to add conductivity for enhancement of electrical stimulation. CNT reduced SF fiber diameters below 1% and effected alignment differently as the concentration increased. Longer degumming times decreased SF fiber diameters and alignment of the same concentration. The optimized conditions were 1 h degumming time with 1.5 ml/h flow rate at a concentration of 100 mg/ml spinning solution with 0.25% CNT to form fibers with 1.36 (± 0.09) µm diameter and 0.31 (± 0.01) a.u. alignment. Additionally, SF fibers were used as a long-term cell growth scaffold to compare with decellularized native tissue. Decellularized tissue decreased fibroblast mRNA expression of collagen type 1, lysyl oxidase-like 1 and matrix metalloproteinase 9, while all other genes expression was the same as cells on plastic. The SF fiber scaffold reduced fibroblast expression of collagen type 3 compared to growth on plastic, and both collagen types 1 and 3 increased over growth time on SF. Immunofluorescence staining showed both collagens newly deposited on the SF scaffold and improved over time. In conclusion, proteins stabilized ICG monomers to improve light interaction, efficacy of photobleaching, and heat evolution to induce apoptosis in neuroblastoma and agglutination of blood in SF composites. Irradiation of ICG enhanced changes in optical properties and may have sensor applications. The decrease of genes may be due to each scaffold having lower stiffness compared to plastic. ICG and SF are both materials with applications as biological scaffolds in pelvic organ prolapse and treatment of neuroblastoma and hemorrhage.
Show less

Title: EMAT DESIGN CONFIGURATIONS AND SOFTWARE-DEFINED ULTRASONIC COMMUNICATIONS THROUGH METALLIC CHANNELS IN NUCLEAR FACILITIES
Creator: Huang, Xin
Date: 2022
Description: Nuclear facilities are partitioned into different blocks, and all equipment therein is well-packed for isolation purposes. The primary...
Show moreNuclear facilities are partitioned into different blocks, and all equipment therein is well-packed for isolation purposes. The primary barriers of each block include a thick, reinforced, high-strength concrete wall. The presence of physical boundaries introduces a major challenge to implementing wired or radio frequency (RF) wireless communication. Achieving data communication through the solids channel, especially considering the complex environment in nuclear power plants, is very challenging. Ultrasonic communication is a desirable method for information transfer through solid mediums such as metallic bars or pipes. This thesis is methodologically innovative in the way it seeks the best solution for ultrasonic communications through metallic channels. Therefore, we address the following research areas: 1. The advantages of using electrical-magnetic acoustic transducers (EMATs) as transmitter and receiver; 2. The fundamentals of the EMAT structure and wave generation mechanism for ultrasonic communications; 3. The channel model and behavior of ultrasonic wave propagation in a different structure of solid channels; 4. How to minimize the adverse impact of wave dispersion and reverberation; 5. How to increase the bitrate and decrease the bit error rate (BER) of an ultrasonic communication system; 6. How to utilize the software-defined system-on-chip (SoC) platform for ultrasonic communications; and 7. How to implement secure ultrasonic video transmission through solid channels. In this thesis, we have investigated the feasibility of using Periodic-permanent-magnet electromagnetic acoustic transducers (PPM-EMATs) transmitter and receiver as the information-bearing of ultrasonic waves across the plate channels (shear horizontal waves) and pipe channels (torsional waves). Methods such as time-reversal (TR), pulse shaping, and adaptive equalizer techniques are studied for improving the signal-to-noise ratio (SNR) of ultrasonic communication systems. We also investigated a novel software-defined ultrasonic communication system (SDUC) for real-time video transmission through a highly reverberant and dispersive metallic bar channel. Furthermore, we investigated the feasibility of combining orthogonal frequency-division multiplexing (OFDM) with quadrature amplitude modulations (QAM) for bitrate peak performance. Strategies and guidelines were established for the best solutions to combat intersymbol interference (ISI) caused by the severe reverberation inherent in metallic channels. A practical solution for video transmission, adhering to the Digital Video Broadcasting Terrestrial (DVB-T) standard, was also examined for video streaming transmission of 240p, 480p, and 720p resolutions at 20 frames per second (FPS) across a rectangular aluminum bar (ARB) channel. Through ultrasonic experimental studies for channel analysis, we achieved a peak video transmission rate of 1074 kbps with 3.3×10-4 BER despite reverberation, the multipath effect, and signal fading within the ARB channel.
Show less

Title: Two Essays on Corporate Finance and Fixed-income Securities
Creator: Shen, Hao
Date: 2023
Description: In this study, we empirically investigate the relation between corporate finance and fixed income securities. Specifically, we employ...
Show moreIn this study, we empirically investigate the relation between corporate finance and fixed income securities. Specifically, we employ staggered changes in state corporate income tax rates as exogenous shocks and estimate how these state tax changes affect bond at-issue yield spreads. We find a significant increase in bond yield spreads after state tax increases but not after state tax decrease. Tax increases result in a 36 basis points increase in the yield spreads, which translates into a $12 million increase in interest expenses for firms experiencing tax increases. Besides, we employ the staggered adoption of universal demand (UD) laws by different states in the United States as a quasi-experimental setting and investigate the effect of UD laws on bond yield spreads at issuance. The adoption of UD laws raises the hurdle for shareholders to bring derivate lawsuits against firms and weakens shareholder litigation rights. Using a sample of bond issuances from 1985 to 2009, we find that the adoption of UD laws is positively associated with yield spreads of bonds issued by U.S. firms.
Show less

Title: Polarization Induced by A Terahertz Electric Field in A Semiconductor Nanodimer in the Overlapping Regime
Creator: Wang, Zi
Date: 2023
Description: Boltzmann transport equation is a theoretical framework for the description of thermodynamics or charge reactions in a system not in...
Show moreBoltzmann transport equation is a theoretical framework for the description of thermodynamics or charge reactions in a system not in equilibrium, which can be applied to the analysis of the interactions of mobile charges with an electromagnetic wave. When the dimensions of the object are small compared to the wavelength, the induced dipole moment provides a means to characterize the collective response while providing insight to the nature of the charge-field interactions. Semiconductor nanoparticles exhibit surface plasmon resonance in the terahertz frequency range and are of current interest for the development of components and circuits in that part of the electromagnetic spectrum. By changing the plasmon frequencies of doped semiconductors through the change of carrier concentration, new opportunities arise for plasmonic manipulation in terahertz region leading to various promising applications. Despite the Drude model's long-term success and convenience in describing the electrical conductivity of metals in terms of dielectric functions, some aspects of polarization are not accounted for by bulk properties. By incorporating the transport equations of the charge carriers with Maxwell's equations, screening effects of charge carriers can be accounted for, enabling the internal field, space charge and induced dipole moment of a semiconductor nanoparticle to be studied.The computations performed for elementary dimer structures in overlapping cases revealed the internal field screening, while the complex dipole moments show dispersion and absorption effects. The numerical algorithms are implemented using the finite element method to investigate the surface plasmon resonance (SPR) induced on the semiconductor particles. Unique SPR modes evolution is observed as the thickness of the overlap region is varied. The characteristics can be interpreted by the migration of local space charge as the level of overlap is varied. This degree of freedom provided by a semiconductor nanodimer could be employed to control the local field near a simple cluster of nanoparticles, with potential for application in sensing and circuit components in the terahertz frequency range.
Show less

Title: Self-Reconfigurable Soft Robots Based on Boundary-Constrained Granular Swarms
Creator: Karimi, Mohammad Amin
Date: 2022
Description: Unlike conventional robots, which consist of rigid bodies and linkages, soft robots are composed of compliant and flexible components and...
Show moreUnlike conventional robots, which consist of rigid bodies and linkages, soft robots are composed of compliant and flexible components and actuators. This distinction enables adaptive behaviors in response to unpredictable environments, like manipulating objects with a variety of shapes. As such, soft robots afford greater potential over traditional robots for safe human interaction.Despite these advantages, there remain obstacles due to the challenges in modeling, controlling, and fabricating soft materials. For example, soft robots that rely on thermal or electrical actuation are typically slow to respond and unable to apply large forces as compared to traditional robots. Pneumatically actuated soft robots, while more responsive and capable of applying larger forces, generally need to be tethered to external control mechanisms, which becomes limiting in tasks that require lightweight, autonomous functionality.In contrast, this thesis describes a new type of robot that exhibits those same characteristics, but achieves them via a boundary-constrained swarm.The robotic structure consists of passive granular material surrounded by an active membrane that is composed of a swarm of interconnected robotic sub-units. The internal components are important for overall function, but their relative configuration is not. This allows for an effectively random, unstructured placement of the internal components, which in turn creates excellent morphability. Collectively, the subunits determine the overall shape of the robot and enable locomotion through interaction with external surfaces.The constrained swarm embodies the continuum, compliant, and configurable properties found in soft robots, but in this state the robot is limited in its ability to manipulate objects due to the relatively low force it can apply to external objects.To address this issue, the unique ability to execute a jamming phase transition is added to the robot. Importantly, jamming is controlled by the degree by which the passive particles are spatially confined by the membrane, and this in turn is controlled by the active sub-unit robots using different jamming mechanisms. The robot exploits its ability to transition between soft (unjammed) and rigid (jammed) states to induce fluid-like flexibility or solid-like rigidity in response to objects and features in the environment.In order to investigate this design concept, I have studied different prototype designs for the robot that varied in terms of the locomotion and jamming mechanisms. I also present a simulation framework in which I model the design and study the scalability of this class of robots. The simulation framework uses the Project Chrono platform, which is a multi-body dynamics library that allows for physics-driven collision and contact modeling.
Show less

Title: Machine Learning for NDE Imaging Applications
Creator: Zhang, Xin
Date: 2023
Description: Infrared Thermography and Ultrasonic Imaging of materials are promising non-destructive evaluation (NDE) methods but signals face challenges...
Show moreInfrared Thermography and Ultrasonic Imaging of materials are promising non-destructive evaluation (NDE) methods but signals face challenges to be analyzed and characterized due to the nature of complex signal patterns and poor signal-to-noise ratios (SNR). Industries such as nuclear energy, are constructed with components produced using high-strength superalloys. These metallic components face challenges for wide deployment because material defects and mechanical conditions need to be non-destructively evaluated to identify potential danger before they enter service. Low NDE performance and lack of automation, particularly considering the complex environment in the in-situation NDE and nuclear power plant, present a major challenge to implement conventional NDE. This study solves the problems of using the advantages of machine learning as signal processing methods for Infrared Thermography and Ultrasonic NDE imaging applications. In Pulsed Infrared Thermography (PIT), for quality control of metal additive manufacturing, we proposed an intelligent PIT NDE system and developed innovative unsupervised learning models and thermal tomography 3D imaging algorithms to detect calibrated internal defects (pores) of various sizes and depths for different nuclear-grade metallic structures. Unsupervised learning aims to learn the latent principal patterns (dictionaries) in PIT data to detect defects with minimal human supervision. Difficulties to detect defects by using PIT are thermal imaging noise patterns; uneven heating of the specimen; defects of micron-level size with overly weak temperature signals and so on. The unsupervised learning methods overcome these barriers and achieve the high defect detection accuracies (F-score) of 0.96 to detect large defects and 0.89 to detect microscopic defects, and can successfully detect defects with diameter of only 0.101-mm. In addition, we researched and developed innovative unsupervised learning models to compress high-resolution PIT imaging data and achieve the average high compression ratio >30 and a highest compression of 46 with reconstruction accuracy peak signal-to-noise ratio (PSNR) >73dB while preserving weak thermal features corresponding to microscopic defects. In ultrasonic NDE imaging, for structural health monitoring of materials, we built a high-performance ultrasonic computational system to inspect the integrity of high-strength metallic materials which are used in high-temperature corrosive environments of nuclear reactors. For system automation, we have been developing neural networks with various architectures for grain size estimation by characterizing the ultrasonic backscattered signals with high accuracy and data-efficiency. In addition, we introduce a response-based teacher-student knowledge distillation training framework to train neural networks and achieve 99.27% characterization accuracy with a high image processed throughput of 192 images/second on testing. Furthermore, we introduce a reinforcement learning based neural architecture search framework to automatically model the optimal neural networks design for ultrasonic flaws detection. At last, we comprehensively researched the performance of using unsupervised learning methods to compress 3D ultrasonic data and achieve high compression performance using only 4.25% of the acquired experimental data.
Show less

Title: INTELLIGENT STREET LIGHTING AND REMOTE POWER UNITS AS CASE STUDIES FOR CITIES TO DECARBONIZE
Creator: Burgess, Patrick G.
Date: 2022
Description: There is a scientific consensus that atmospheric warming caused by the release of emissions will reach critical levels in our lifetime if...
Show moreThere is a scientific consensus that atmospheric warming caused by the release of emissions will reach critical levels in our lifetime if significant efforts are not made to decarbonize our buildings and power grid. The City of Los Angeles is a prime example of the challenges of decarbonizing, balancing global, federal, and state policies and issues and addressing environmental justice. The first research case studies of the details and challenges of decarbonization efforts include the implementation of the first networked light-emitting diode (LED) streetlights in the city of Chicago on IIT’s campus to improve the reliability and economics of its main campus, 2.5 mi south of downtown Chicago. Research shows that these networked LED streetlights greatly reduce a city's rising energy costs, but the CSMART project team has set out to prove the benefits of integrating an intelligent communications and control system with an existing smart grid infrastructure, such as an existing network and supervisory control and data acquisition (SCADA) systems. In addition to assessing the economic and environmental drivers for the intelligent streetlight solution, the project team is dedicated to assessing the potential cybersecurity vulnerabilities of such a system and working to mitigate or eliminate them. The second research case study covers off-grid remote power units providing continuous illumination for safer streets and safer driving that is unaffected by power outages. Thanks to individual lighting control potentially allowing for dimming, blinking, and even color changing, streetlights powered by RPUs can be used as emergency signaling devices, directing traffic during a city evacuation or other emergency. The RPU control and monitoring can be accessed through the cloud, thereby avoiding reliance on local servers.
Show less

repository.iit

Search the repository

Pages

Pages