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Title: Design and Synthesis of New Sulfur Cathodes Containing Polysulfide Adsorbing Materials
Creator: Suzanowicz, Artur M
Date: 2023
Description: Lithium-sulfur battery (LSB) technology has tremendous prospects to substitute lithium-ion battery (LIB) technology due to its high...
Show moreLithium-sulfur battery (LSB) technology has tremendous prospects to substitute lithium-ion battery (LIB) technology due to its high theoretical specific capacity and energy density. However, escaping polysulfide intermediates (produced during the redox reaction process) from the cathode structure is the primary reason for rapid capacity fading. Suppressing the polysulfide shuttle (PSS) is a viable solution for this technology to move closer to commercialization and supersede the established LIB technology. In this dissertation, I have analyzed the challenges faced by LSBs and selected methods and materials to address these problems. I have concluded that in order to further pioneer LSBs, it is necessary to address these essential features of the sulfur cathode: superior electrical conductivity to ensure faster redox reaction kinetics and high discharge capacity, high pore volume of the cathode host to maximize sulfur loading/utilization, and polar polysulfide-resistive materials to anchor and suppress the migration of lithium polysulfides.Furthermore, a versatile, low-cost, and practical scalable synthesis method is essential for translating bench-level development to large-scale production. This dissertation covers designing and synthesizing new scalable cathode structures for lithium-sulfur batteries that are inexpensive and highly functional. The rationally chosen cathode components accommodate sulfur, suppress the migration of polysulfide intermediates via chemical interactions, enhance redox kinetics, and provide electrical conductivity to sulfur, rendering excellent electrochemical performance in terms of high initial specific capacity and good long-term cycling performance. TiO2, Ni12P5, and g-C3N4 as polysulfide adsorbing materials (PAMs) have been fully studied in this thesis along with three distinct types of host structures for lithium-sulfur batteries: Polymer, Carbon Cloth, and Reduced Graphene Oxide. I have created adaptable bulk synthesis techniques that are inexpensive, easily scalable, and suitable for bench-level research as well as large-scale manufacturing. The exceptional performance and scalability of these materials make my cathodes attractive options for the commercialization of lithium-sulfur batteries.
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Title: DUST MITIGATION OF MICRO-STRUCTURED (GECKO-LIKE) ADHESIVES
Creator: Alizadehyazdi, Vahid
Date: 2019
Description: Controllable adhesives (i.e. those capable of being turned on and off) are used in a wide range of applications including robotic grippers and...
Show moreControllable adhesives (i.e. those capable of being turned on and off) are used in a wide range of applications including robotic grippers and climbing robots. Electromagnets, suction, and microspines have been used to meet this demand, but are typically limited to a specific substrate roughness or material. Microstructured (gecko-like) adhesives on the other hand, offer the potential to be the most universal among controllable adhesives since they can work on a wide variety of surfaces. The development of microstructured (gecko-like) adhesives has focused almost solely on their adhesive strength. However, for practical applications, especially in real-world environments, the adhesive's long-term performance is arguably equally important. One impediment to long-term viability is the adhesive's susceptibility to contamination, which decreases adhesion significantly. To have practical microstructure adhesives in real-world environments, the detrimental effect of dust and other contaminants should be dealt with. The first general approach involves removing adhered dust particles. The second approach is to create adhesives that minimize dust adsorption such that extensive cleaning is not necessary or they can be removed easily. Regarding the first approach, this research describes the use of electrostatic forces and ultrasonic vibration to repel dust particles. Results are non-destructive, non-contact cleaning methods that can be used in conjunction with other cleaning techniques, many of which rely on physical contact between the fibrillar adhesive and substrate. Electrostatic cleaning results show that a two-phase square wave with the lowest practically feasible frequency has the best cleaning results. Combining electrostatic and ultrasonic cleaning results in far higher efficiency than when using electrostatic repulsion or ultrasonic alone. Moreover, I showed that the piezoelectric element in the ultrasonic cleaning method can also be used as a releasing mechanism to turn the adhesive off and as a force/contact sensor. Regarding the second approach, I experimentally explored the effect of the modulus of elasticity, work of separation, and work of adhesion (adhesion energy) on the shear stress and particle detachment capabilities of microstructured adhesives. Particle removal is evaluated using both non-contact cleaning methods (centripetal force and electrostatic particle repulsion) and a dry contact cleaning method (load-drag-unload test). Results show that for a material with a high work of separation, high elastic modulus, and low work of adhesion, it is possible to create a microstructured adhesive with both high shear stress strength and low adhesion to dust particles. Results also show that, for dry contact cleaning, shear stress recovery mostly stems from particle rolling and not particle sliding. Moreover, shear test results show that augmenting the microstructured adhesive with electrostatic adhesion can reduce the negative effects on adhesion of a high elastic modulus materials' conformability to a substrate by providing a preload to the microstructured elements. Finally, I applied mentioned dust mitigation methods on two different gecko-like adhesives grippers. The first design was used to pick up flat objects, while the second one is designed to grip curved objects of different shapes and sizes. Since the second gripper is flexible and piezoelectric is stiff (it can only be applied to rigid backings), only electrostatic dust mitigation is applicable.
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Title: UNDERSTANDING THE FUNDAMENTAL MECHANISMS OF MESO-SCALE ENGINEERING OF GRAIN BOUNDARIES IN NI-BASE SUPERALLOYS
Creator: Alabbad, Bader
Date: 2019
Description: Polycrystalline nickel base superalloys are known to possess high temperature strength, good crack growth resistance and corrosion resistance...
Show morePolycrystalline nickel base superalloys are known to possess high temperature strength, good crack growth resistance and corrosion resistance at high temperatures. Engineering the morphology of the grain boundaries can yield to extent the high temperature resistance for polycrystalline nickel-based superalloys. Meso-scale engineering for grain boundary structures can be utilized through the development of serrated grain boundaries to improve the damage tolerance of polycrystalline nickel- based superalloys. Grain boundary precipitates induce the formation of the grain boundary serrations as precipitates protrude the grain boundary. Understanding and controlling the cooling processes from above the solvus temperature plays an important role in controlling the size and population of γ′ precipitates to modify specific microstructural features that can impact the resulting properties. Two stepped cooling process with a transition just below the γ′ solvus has the ability to form a unique microstructure as heterogeneous nucleation and growth of large γ′ precipitates along the grain boundaries during the initially slow cooling rate. The eventual transition to a standard or conventional cooling rate will then govern the formation of the secondary, intragranular γ′ precipitates. The stepped cooling process was compared to the conventional fast continuous cooling process. The effect of grain boundary misorientation on the precipitation behavior of grain boundary γ′ precipitates revealed coarse grain boundary γ′ precipitates reside along high angle grain boundaries. Mechanical testing was carried out to investigate their mechanical properties to compare and benchmark to those produced via conventional continuous cooling to quantify the extent by which serrated boundaries can be used to improve the properties where the modified microstructures led to great high temperature properties.Nickel-base superalloy 718Plus is a recently developed alloy that is being considered for use in a number of advanced gas turbine engine applications. A constructed heat treatment was proposed to drive the precipitation of fine η precipitates along grain boundaries. Lamellar η phase precipitates were able to induce the formation of serrated grain boundaries. Discontinuous cellular precipitation reaction led the formation of the lamellar η phase precipitates. The characteristic growth of lamellar η phase precipitates was influence by the grain boundary structure. Creep tests were carried out to provide a better understanding of how serrated grain boundaries formed using η phase precipitates can impact the creep properties of ATI 718Plus.
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Title: Feasibility and Properness in Linear Interference Alignment: Flow Tests, Sufficient Conditions, and Approximation Algorithms.
Creator: Al-Dhelaan, Fahad Abdullah
Date: 2019
Description: Interference forms a major challenge in our understanding of the capacity of wireless networks and our ability to achieve this capacity....
Show moreInterference forms a major challenge in our understanding of the capacity of wireless networks and our ability to achieve this capacity. Rather than scheduling transmissions to avoid interference, recent techniques allow for interference to be neutralized and for simultaneous transmission of messages.Linear interference alignment in MIMO networks is the technique of aligning messages, by the transmitters through the use of precoding matrices, so that the undesired messages occupy some minimal sub-space upon their arrival at an unintended receiver. The overlapping of the sub-spaces where these interfering messages fall allows the receiver to neutralize them with minimal dedication of its resources through the application of a decoding matrix.The linear interference alignment problem is to design these precoding and decoding matrices. It has been shown to be NP-hard in the literature.A network is called feasible if such a solution exists. Even deciding whether some network instance is feasible, is non-trivial. The problem of deciding feasibility was shown to be NP-hard in the literature, for constant channel coefficients.We focus on finding efficient and robust feasibility tests in the case of generic channels, where the computational complexity is unknown. We provide efficient and robust tests for the necessary condition of properness, which had previously been identified in the literature but given no efficient tests in the general case.We identify several conditions, each being sufficient for feasibility. We study their relationships and the computational complexity of testing for them. We provide polynomial-time maximum flow test for one sufficient condition in the case of uniform demands. In the case of uniform demands which divide the number of antennas at all receivers or all transmitters, we show that these sufficient and necessary conditions are equivalent with feasibility, thereby admitting efficient maximum-flow tests.We identify a subset of feasible instances where the decoding and precoding matrices can be designed in polynomial-time. Furthermore, we show that any proper instance is within a constant factor of a one of these instances. Then, we provide efficient constant approximation algorithms for the problems of maximizing demand and minimizing antennas such that an instance is feasible.
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Title: DEEP LEARNING FOR IMAGE PROCESSING WITH APPLICATIONS TO MEDICAL IMAGING
Creator: Zarshenas, Amin
Date: 2019
Description: Deep Learning is a subfield of machine learning concerned with algorithms that learn hierarchical data representations. Deep learning has...
Show moreDeep Learning is a subfield of machine learning concerned with algorithms that learn hierarchical data representations. Deep learning has proven extremely successful in many computer vision tasks including object detection and recognition. In this thesis, we aim to develop and design deep-learning models to better perform image processing and tackle three important problems: natural image denoising, computed tomography (CT) dose reduction, and bone suppression in chest radiography (“chest x-ray”: CXR). As the first contribution of this thesis, we aimed to answer to probably the most critical design questions, under the task of natural image denoising. To this end, we defined a class of deep learning models, called neural network convolution (NNC). We investigated several design modules for designing NNC for image processing. Based on our analysis, we design a deep residual NNC (R-NNC) for this task. One of the important challenges in image denoising regards to a scenario in which the images have varying noise levels. Our analysis showed that training a single R-NNC on images at multiple noise levels results in a network that cannot handle very high noise levels; and sometimes, it blurs the high-frequency information on less noisy areas. To address this problem, we designed and developed two new deep-learning structures, namely, noise-specific NNC (NS-NNC) and a DeepFloat model, for the task of image denoising at varying noise levels. Our models achieved the highest denoising performance comparing to the state-of-the-art techniques.As the second contribution of the thesis, we aimed to tackle the task of CT dose reduction by means of our NNC. Studies have shown that high dose of CT scans can increase the risk of radiation-induced cancer in patients dramatically; therefore, it is very important to reduce the radiation dose as much as possible. For this problem, we introduced a mixture of anatomy-specific (AS) NNC experts. The basic idea is to train multiple NNC models for different anatomic segments with different characteristics, and merge the predictions based on the segmentations. Our phantom and clinical analysis showed that more than 90% dose reduction would be achieved using our AS NNC model.We exploited our findings from image denoising and CT dose reduction, to tackle the challenging task of bone suppression in CXRs. Most lung nodules that are missed by radiologists as well as by computer-aided detection systems overlap with bones in CXRs. Our purpose was to develop an imaging system to virtually separate ribs and clavicles from lung nodules and soft-tissue in CXRs. To achieve this, we developed a mixture of anatomy-specific, orientation-frequency-specific (ASOFS) expert deep NNC model. While our model was able to decompose the CXRs, to achieve an even higher bone suppression performance, we employed our deep R-NNC for the bone suppression application. Our model was able to create bone and soft-tissue images from single CXRs, without requiring specialized equipment or increasing the radiation dose.
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Title: Numerical and Experimental Investigation to Improve Radio Frequency Performance of Photonic Band Gap Accelerating Structure
Creator: Zhou, Ning
Date: 2019
Description: In this thesis, the design and experimental work of a Photonic Band Gap (PBG) accelerator cavity with star-shape array is presented. Photonic...
Show moreIn this thesis, the design and experimental work of a Photonic Band Gap (PBG) accelerator cavity with star-shape array is presented. Photonic band gap structures (metallic and/ or dielectric) have been proposed for accelerator applications. These structures act like filters, allowing electromagnetic waves propagating at some frequencies to be transmitted through the lattice, while rejecting the RF fields in some (unwanted) frequency range. Additionally PBG structures are used to support selective field patterns (modes) in a resonator or waveguide by a defect region within the lattice; while damping unwanted higher- or lower-order modes without impacting the supported mode. The unwanted modes affect beam propagation or even distort the beam. Thus, suppression of unwanted modes is important. In this thesis work, a star shape structure is obtained from removing elements in a PBG structure with triangular lattice and employed for integration with a metallic cavity resonator for accelerator applications. Impedance matching is accomplished by adjustment of positions of some elements in the array. The design was fabricated and measured to have an input return loss of over 30 dB at the targeted frequency of 11.4GHz. The measured results are in an excellent agreement with the computer simulation.
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Title: EVALUATING INTEGRITY FOR MOBILE ROBOT LOCALIZATION SAFETY
Creator: Duenas Arana, Guillermo
Date: 2019
Description: Precise localization is paramount for autonomous navigation. Localization errors are not only dangerous by themselves, but can also mislead...
Show morePrecise localization is paramount for autonomous navigation. Localization errors are not only dangerous by themselves, but can also mislead other dependent systems into moving to a hazardous location. Unfortunately, the problem of quantifying robot localization safety is only sparsely addressed in the robotics literature, and most robotics algorithms still quantify pose estimation performance using a covariance matrix or particle spread, which only accounts for nominal sensor errors. This is insufficient for life- and mission-critical applications, such as autonomous vehicles and other co-robots, where ignoring sensor or sensor or processing faults can lead to catastrophic localization errors. Thus, other methods must be employed to ensure safety.In response, this research leverages prior work in aviation integrity monitoring to tackle the more challenging case of evaluating localization safety in mobile robots. In contrast to aviation applications, that heavily rely on the Global Navigation Satellite System (GNSS) for localization, robots often operate in complex, GNSS-denied environments that require a more sophisticated sensor suite to ensure localization safety. Localization integrity risk is the probability that a robot's pose estimate lies outside pre-defined acceptable limits while no alarm is triggered. In this work, the integrity risk is rigorously upper bounded by accounting for both nominal noise and other non-nominal sensor faults, resulting in a safe upper bound on the localization integrity risk.The main contribution of this dissertation is the design and evaluation of a sequential integrity monitoring methodology applicable to mobile robot localization algorithms that use feature extraction and data association. First, faults introduced during the feature extraction and data association processes are distinguished, and the probability of the latter is rigorously upper bounded using analytical methods. The impact of faults in the estimate error's and fault detector's distributions is then determined to quantify integrity risk, which is evaluated under the worst-possible fault combination. To determine the impact of previous faults without a boundlessly growing number of fault hypotheses, this dissertation presents a novel method that uses a preceding time window to build a limited set of hypotheses and a prior estimate bias to account for faults occurring before the start of the time window. The proposed methodology is applicable to Kalman Filter and fixed-lag smoothing localization. Simulated and experimental results are presented to validate the methodology.
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Title: SIMULATION OF H2A.B CONTAINING HISTONE VARIANT NUCLEOSOME
Creator: Kohestani, Havva
Date: 2019
Description: The H2A.B histone is a highly evolving vertebrate specific variant of the H2A histone family. It has been implicated in increased gene...
Show moreThe H2A.B histone is a highly evolving vertebrate specific variant of the H2A histone family. It has been implicated in increased gene expression, and experiments have shown that incorporation of H2A.B into nucleosomes results in more extended structures with fewer wrapped DNA base pairs. To study the molecular mechanisms of H2A.B, we have performed a series of conventional and enhanced sampling molecular dynamics simulation of H2A.B and canonical H2A containing nucleosomes.Results of adaptively biased molecular simulations show that substitution of canonical H2A with H2A.B results in geometrical changes such as unwrapping of 10 to 15 base pairs of DNA on each side of the nucleosome and an increase in the diameter and radius of gyration, which is in agreement with previous AFM, FRET, and SAXS experiments. DNA unwinding is energetically favorable in H2A.B containing compared to canonical nucleosomes, while in both systems we observe a wide range of sampling over various structures of DNA. H3 histone tails excluded simulations, show the importance and effect of N-terminal residues of H3 histones on attachment of DNA at the entry/exit sites to nucleosome protein core. Clustering and hydrogen bond analysis suggest that introduction of H2A.B to nucleosome systems triggers mechanisms leading to rearrangement of hydrogen bond network which may influence the pattern and intensity of interactions between DNA-protein and protein-protein complexes.
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Title: CHARACTERIZATION OF VERY LARGE YET VERY MILD BMD TYPE EDITS OF DYSTROPHIN
Creator: Lin, Yi-hsiu
Date: 2014, 2014-12
Description: Duchenne muscular dystrophy, DMD, is a severe X-linked recessive disease that kills boys in their second or third decade of life. A related...
Show moreDuchenne muscular dystrophy, DMD, is a severe X-linked recessive disease that kills boys in their second or third decade of life. A related condition Becker Muscular Dystrophy, BMD, is very heterogeneous with clinical severity ranging from nearly as bad as DMD, to nearly benign. Both of these are caused by defects in the dystrophin gene, which encodes a 427 kDa cytoskeletal protein, dystrophin, which can provide a mechanical link between the cytoskeleton and the muscle membrane and stables muscle tissue. In general, DMD results from defects that eliminate all dystrophin expression, whereas BMD patients carry mutated products: modified and malfunctioned dystrophin proteins. Since DMD is invariably fatal, monogenic, has a high incidence (1:3500 male births) and afflicts a charismatic patient profile, it has been an attractive target for gene therapy. However, the huge size of the dystrophin gene (2.4 Mbp) and more importantly its processed mRNA (14.2 kb) poses a problem for viral gene therapy which is limited to payloads of about 8 kb. This has prompted efforts to reduce the size of the dystrophin protein while still maintaining functionality. A major inspiration for such efforts was the identification of a very unusual, very large deletion serendipitously found in an extremely mild BMD case. The patient identified with this defect was ambulatory at 65 year of ages. This edit removes more than half the central rod region, from exon 17 to 48, Δe17-48, and, fortunately, the size of this BMD type edit protein is available for viral vector loading. In this project, edited dystrophin with central rod region deletion (D2:22 Δe17-48) and other two related edits, D2:22 Δe17-47 (exon 48 is added in D2:22 Δe17-48) and D2:22 Δe17-49 (exon 49 is deleted from D2:22 Δe17-48), were studied. According to these results, D2:22 Δe17-47 demonstrated the best biophysical and biochemical properties, but D2:22 Δe17-48 displayed higher to protease sensitivity, and D2:22 Δe17-49 had the worst thermal stability. This work will help us to understand the factors that result in benign large scale edits, and facilitate the development of effective viral gene therapy vectors.
M.S. in Biology, December 2014
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Title: THERMODYNAMICS AND PHASE EQUILIBRIA OF HEUSLER ALLOYS
Creator: Chung, Yoonsung
Date: 2011-09, 2011-07
Description: Heusler compounds are of great interest for their properties such as shape memory, thermoelectric, ferromagnetic and spin polarization effects...
Show moreHeusler compounds are of great interest for their properties such as shape memory, thermoelectric, ferromagnetic and spin polarization effects that could lead to new mechanical and electronic devices. Currently, the study of Heusler alloys is focused on their electronic and magnetic properties, but the high temperature thermodynamic properties of these compounds have not been covered as much. A thorough knowledge of the thermodynamic properties and phase equilibria is required for developing this kind of alloys. This thesis is part of a systematic investigation of the thermodynamics and phase equilibria of ternary Heusler alloy systems. In this work, the high temperature reaction calorimeter was used to obtain the standard enthalpy of formation of compounds in the Ni2XSn (X = Ti, Zr, Hf, V and Nb) and Ni2TiX (X = Ga and In) ternary systems. It was confirmed the compound Ni2TaSn does not exist in the Heusler structure A Setaram Ligne 96 drop calorimeter was used to measure the heat content of Ni2TiSn as a function of temperature. Phase equilibria and crystal structures of Ni2TiSn, Ni2TiGa and Ni2TiIn were determined using XRD, SEM and EDS.
M.S. in Materials Science & Engineering, July 2011
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Title: AN INTRINSICALLY CONDUCTING POLYMER-BASED COATING SYSTEM FOR CORROSION PROTECTION OF STEELS
Creator: Yu, Qifeng
Date: 2016, 2016-12
Description: Among the various corrosion protection strategies for structural steels, coating techniques provide the most cost-effective protection and...
Show moreAmong the various corrosion protection strategies for structural steels, coating techniques provide the most cost-effective protection and have been used as the primary mode for corrosion protection. Existing coating techniques have been used mainly for their barrier capability and all have a limited service life. In this research work, a waterborne two-strand polyaniline: poly (acrylic acid) complex was synthesized and utilized to fabricate the primer layer of a two-layer coating system. The techniques of Scanning Kelvin Probe Force Microscopy (SKPFM) and Electrochemical Impedance Spectroscopy (EIS) were used to evaluate the anti-corrosion capability of the polymeric complex when mixed in an epoxy matrix and coated on steel samples as the primer layer. The evaluation results show that coating systems including a PANi-based primer has measurable anticorrosion capability and the anti-corrosion capability of PANi-based primer depends on the usage of PANi and the type of matrix material of the primer layer. In the laboratory condition, a prototype two-layer coating system including the PANi-based primer and a polyurethane topcoat was manufactured. The ASTM Salt-Spray Test and EIS were used to prove the anti-corrosion performance of the prototype using a two-layer, polyurethane-over-epoxy system (no PANi) as the control system. After the proof of concept, a non-waterborne epoxy was used to fabricate a different PANi-based primer. The two types of primers and two other commercial primers (a zinc-rich primer and an epoxy-only primer) were used to make a total of eight two-layer coating systems using two widely used topcoats. Salt-Spray Test, Cyclic Salt Fog/UV Exposure Test, Pull- Off Adhesion Test, and the techniques of EIS, SKPFM, and Scanning Electron Microscope (SEM) were used to evaluate the long-term performance of the eight systems. Based on the laboratory-based recommendations, six groups of two-layer coating systems were then subjected to the outdoor-exposure test to evaluate their anti-corrosion durability at two testing sites. The field durability of the coating systems was evaluated in terms of their surface gloss reduction, color change, adhesion change and surface deteriorations. The matrix material in which the PANi is mixed plays an important role in the longterm anti-corrosion performance of coatings. The waterborne epoxy is effective in dispersing PANi nano-particles and has zero VOC; however, it does not bond to the steel surface as strongly as the regular non-waterborne epoxy. The topcoat material also plays an important role in the long-term anti-corrosion performance of coatings; polyurethane has higher durability than epoxy as a topcoat material. The PANi-based systems possess long-term corrosion protection comparable to the performance of the conventional zincrich three-layer system based on the one-year field evaluation.
Ph.D. in Civil Engineering, December 2016
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Title: FINFET BASED STANDARD CELL LIBRARY CHARACTERIZATION
Creator: Yuan, Yu
Date: 2015, 2015-07
Description: In this work, four standard cell libraries based on FinFET technology have been characterized and implemented. The first library uses the BSIM...
Show moreIn this work, four standard cell libraries based on FinFET technology have been characterized and implemented. The first library uses the BSIM-CMG and PTM-MG models, which represents the common multi-gate devices. Two libraries are based on the BSIM-IMG model, operating in short-gate (corresponding to low-Vt) mode and lowpower (corresponding to high-Vt) mode separately. Synthesis and simulation of BSIMCMG based library is presented and compared to the conventional 45nm CMOS library, FreePDK45. The results show acceptable accuracy of the library based on BSIM-CMG model. For the libraries based on BSIM-IMG model, Short-Gate (SG) mode, Low-Power (LP) mode and the mixed-mode (combining both SG and LP modes) have been analyzed. The results proved that the low-power independent multi-gate FinFET can be used for leakage power reduction, just like the bulk CMOS high-Vt devices. At the end of this work, another library based on CCS model was characterized and verified, which show far better accuracy in terms of both timing and power modeling.
M.S. in Electrical Engineering, July 2015
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Title: DEGRADATION RATE MODEL TO ESTIMATE SOIL CARBON SEQUESTRATION
Creator: Zhai, Wenjuan
Date: 2016, 2016-05
Description: Concern over climate change as a consequence of carbon dioxide (CO2) emissions from human activities has resulted in efforts to better...
Show moreConcern over climate change as a consequence of carbon dioxide (CO2) emissions from human activities has resulted in efforts to better understand potential mitigation measures such as carbon sequestration in soils. Processes shaping natural carbon sequestration may be used to remove excess CO2 from combustion and other anthropogenic sources of carbon, and, alleviate concerns over climate change. Land application of biosolids is a process that increases the amount of soil carbon sequestration and may produce carbon credits in accordance with the definition of UN Climate Change Convention. A dynamic degradation rate model (DRM) has been developed based on a mass balance and first order kinetics to describe the soil organic carbon (SOC) decomposition process, which provides insights on carbon sequestration due to microbial biomass, SOC, CO2 emission rates, residence time of sequestered carbon, and biomass to biosolids ratios. A curve fitting approach was used to produce a best fit average degradation rate for biosolids degradation and microbial biomass yield. This study employed a 34-year biosolids application database from the literature to determine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory resultsdetermine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory resultsdetermine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory resultsdetermine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory results provided by a yearlong study indicates that higher temperatures and moisture content and finer soils are related to larger degradation rates. To summarize, this study has the following contributions: (1) developed a degradation rate model which simulates the biosolids degradation process in soil and identifies two SOC phases in soil, and quantifies the biosolids degradation rate constant, biomass yield, and the C sequestered amount for multiple and long term soil application; (2) assessed the effect of changes in the amount of biosolids applied, soil type, and weather conditions on the C degradation rate by comparing model results to laboratory data; and (3) provides an easy quantitative method for predicting C sequestration from biosolids added to soil.
Ph.D. in Environmental Engineering, May 2016
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Title: DETECTION OF SUPEROXIDE ANION RADICALS IN ANION EXCHANGE MEMBRANE FUEL CELLS USING IN-SITU FLUORESCENCE SPECTROSCOPY
Creator: Zhang, Yunzhu
Date: 2016, 2016-07
Description: Anion exchange membrane (AEM) stability is a long-standing challenge that has limited the widespread development and adoption of AEM fuel...
Show moreAnion exchange membrane (AEM) stability is a long-standing challenge that has limited the widespread development and adoption of AEM fuel cells. It is essential to understand the mechanism of AEM degradation during fuel cell operation. There are multiple modes of AEM degradation, broadly classified as chemical, mechanical and thermal degradation. Chemical degradation is among the most destructive modes, and can be further sub-divided into nucleophilic degradation (induced by the hydroxide ion), and oxidative degradation (induced by reactive oxygen species). While the former has been extensively studied, there is minimal work on oxidative AEM degradation. The reactive oxygen chemical species produced during the operation of an AEM fuel cell have hitherto not been detected during operation. Given the high pH, it is postulated that superoxide anion radicals (𝑂2∙−), as opposed to hydroxyl radicals, are primarily involved in the degradation progress. The objective of this study was to confirm the 𝑂2∙− formation during AEM fuel cell operation and to monitor in real-time the rate of 𝑂2∙− generation in an operating fuel cell using in-situ fluorescence spectroscopy. 1,3-diphenlisobenzofuran (DPBF) was chosen as the fluorescence probe, the sensitivity of which towards 𝑂2∙− was evaluated by performing ex-situ experiments in a semi-batch reactor. We demonstrate that the fluorescence intensity of this dye selectively decreased upon exposing 𝑂2∙−. DPBF was then incorporated into an AEM (membrane was solution cast after mixing the dye with the casting solution), which was assembled into a fuel cell. 𝑂2∙− generation in an operating AEM fuel cell was then monitored via in-situ fluorescence spectroscopy using a bifurcated optical probe, when the cell was operated in H2/O2 mode. To confirm the impact of 𝑂2∙− on AEM degradation, independent experiments (without dye) were performed under identical conditions, under both H2/O2 and N2/N2 modes, and the ionic conductivity and ion exchange capacity were monitored to estimate degradation extent. From our in-situ fluorescence studies, we were able to estimate the rate constants and activation energy for oxidative AEM degradation in an operating AEM fuel cell.
M.S. in Chemical Engineering, July 2016
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Title: BIG DATA SYSTEM INFRASTRUCTURE AT EXTREME SCALES
Creator: Zhao, Dongfang
Date: 2015, 2015-07
Description: Rapid advances in digital sensors, networks, storage, and computation along with their availability at low cost is leading to the creation of...
Show moreRapid advances in digital sensors, networks, storage, and computation along with their availability at low cost is leading to the creation of huge collections of data { dubbed as Big Data. This data has the potential for enabling new insights that can change the way business, science, and governments deliver services to their consumers and can impact society as a whole. This has led to the emergence of the Big Data Computing paradigm focusing on sensing, collection, storage, management and analysis of data from variety of sources to enable new value and insights. To realize the full potential of Big Data Computing, we need to address several challenges and develop suitable conceptual and technological solutions for dealing them. Today's and tomorrow's extreme-scale computing systems, such as the world's fastest supercomputers, are generating orders of magnitude more data by a variety of scienti c computing applications from all disciplines. This dissertation addresses several big data challenges at extreme scales. First, we quantitatively studied through simulations the predicted performance of existing systems at future scales (for example, exascale 1018 ops). Simulation results suggested that current systems would likely fail to deliver the needed performance at exascale. Then, we proposed a new system architecture and implemented a prototype that was evaluated on tens of thousands nodes on par with the scale of today's largest supercomputers. Micro benchmarks and real-world applications demonstrated the e ectiveness of the proposed architecture: the prototype achieved up to two orders of magnitude higher data movement rate than existing approaches. Moreover, the system prototype was incorporated with features that were not well supported in conventional systems, such as distributed metadata management, distributed caching, lightweight provenance, transparent compression, acceleration through GPU encoding, and parallel serialization. Towards exploring the proposed architecture at millions of node scales, simulations were conducted and evaluated with a variety of workloads, showing near linear scalability and orders of magnitude better performance than today's state-of-the-art storage systems.
Ph.D. in Computer Science, July 2015
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Title: SYNTHESIS OF NANOPLATE STRUCTURES IN NI-BASED ALLOYS VIA DISCONTINUOUS PRECIPITATION
Creator: Zhou, Yang
Date: 2017, 2017-07
Description: Nanostructured materials are of increasing interest due to their potential for use in numerous applications including catalysis and filtration...
Show moreNanostructured materials are of increasing interest due to their potential for use in numerous applications including catalysis and filtration. Methods of synthesizing nanomaterials often include chemical techniques producing individual particles, which gives rise to issues of agglomeration and containment, and the processes are difficult to scale-up. This work is directed at addressing issues of the occurrence and kinetics of self-assembly and structural alignment of nanostructures, which involves the discontinuous precipitation transformation followed by selective dissolution. This synthesis method has been demonstrated using a Ni-49at.%Co-12at.%Al alloy. A complete discontinuous transformation in the Ni 49-12 alloy can be achieved in times as short as 30min. Thus, the large-scale production of such structures is feasible using conventional heat treatment facilities. The synthesis technique is generally applicable to any alloy system in which DP goes to completion and one phase can be selectively removed. The nanoplates are self-assembled, self-supported and well aligned if the precipitate is coherent with the matrix. In order to control the process it is necessary to understand the phase equilibria involving γ, γ′ and β phases in the Al-Co-Ni system. This has been investigated both experimentally and computationally. The isothermal sections at 1100°C and 800°C as well as a partial liquidus projection were determined which result in modifications to previously published work. Comparing the experimental results with the calculated results using Thermo-Calc (TCNI8), there is reasonable agreement. The predicted separation of the γ phase into a two-phase ferromagnetic and paramagnetic region has never been observed experimentally in this or other published work. Future work should explore the ferromagnetic and paramagnetic phase separation as predicted using Thermo-Calc to verify its occurrence in this system. The nanostructured material produced by complete DP transformation may have interesting mechanical properties and these have been studied to a limited extent in this work. The hardness tests show that with decreasing annealing temperature to 600°C, the hardness of certain samples increases significantly due to the precipitation of second phase. The tensile and creep properties of alloy samples with DP phase present were also investigated. The results imply that the occurrence of DP will have a favorable effect on the tensile strength of the sample while lowering the ductility at the same time. A method to generate serrated grain boundaries based on the DP transformation is proposed. Such structures are expected to increase the creep resistance. This was found to be the case in a limited temperature and loading range. Higher temperature or stress levels lead to DP occurrence and cause negative effects on the creep resistance compared to conventionally processed material. The Curie temperature in the Al-Co-Ni alloy system was also studied and determined using a combined magnetic TG and DSC method. A ternary contour map of the Curie temperature has been constructed. From the contour map, the Curie temperature was seen to decrease from high Co, low Al content samples to low Co, high Al samples bypassing a platform at mid Co content. A nonlinear surface fitting was made through a Exponential2D model, the function is helpful for the prediction of Curie temperature of γ phase in Al-Co-Ni alloy system. This method also provides a novel idea of detecting phase transformation and precipitation through thermo-magnetically analyzing the magnetic behavior of the alloys.
Ph.D. in Materials Science and Engineering, July 2017
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Title: A STEP TOWARD SUPPORTING LONG-RUNNING APPLICATIONS WITH REAL-TIME CONSTRAINTS ON HYBRID CLOUDS
Creator: Wu, Hao
Date: 2017, 2017-05
Description: The advancement of computer and network technology has brought the world into a new computer cloud era. The ”pay-as-you-go” business model and...
Show moreThe advancement of computer and network technology has brought the world into a new computer cloud era. The ”pay-as-you-go” business model and the service oriented models allow users to have ”unlimited” resources if needed and free from infrastructure maintenance and software upgrades. Cloud services are currently among the top-ranked high growth areas in computing and are seeing an acceleration in enterprise adoption with the worldwide market predicted to reach more than $270b in 2020. According to Google, currently more than 95% of the web services are deployed on cloud.Many di↵erent types of applications are deployed on computer clouds. However, due to inherent performance uncertainty within computer clouds, as of today, applications with real-time and high QoS constraints still operate on traditional computer systems and are not able to benefit from elastic computer clouds.. The thesis focuses on both theoretical analysis and real system implementation on the problem of guaranteeing real-time application’s deadline requirement while minimizing the application’s execution cost on hybrid clouds. Four major problems have been addressed towards moving applications with real-time constraint on hybrid computer clouds. 1). A minimal slack time and minimal distance (MSMD) scheduling algorithm is developed to minimize the resources needed to guarantee an application’s end-to-end deadline requirement using computer clouds. 2). A VM Instance Hour Minimization (IHM) algorithm is developed to reduce the application’s execution cost for given schedules. The proposed IHM algorithm can be integrated with common scheduling algorithm used in the literature. In addition, we also evaluated the feasibility of utilizing spot instance to further reduce the application’s execution cost while not sacrificing QoS guarantees. 3). A reference model for virtual machine launching overhead is developed to predict both system utilization and timing overhead during the VM launching process. 4). A hybrid cloud management tool that integrates the developed algorithms and reference model is developed to support running long-running applications with real-time constraints on hybrid clouds.
Ph.D. in Computer Science, May 2017
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Title: URBAN SPRAWL AND SUSTAINABLE DEVELOPMENT IN CHINA
Creator: Wang, Xiaoxiao
Date: 2012-07-11, 2012-07
Description: Compared to the rich literature on urban sprawl in Western cities, relatively little is known of the driving factors, processes, and future...
Show moreCompared to the rich literature on urban sprawl in Western cities, relatively little is known of the driving factors, processes, and future trends of urban sprawl in China. This research will analyze the socio-economic forces behind two parts of urban sprawl in China: urban decentralization (the creation of development zones and new towns) and urban renewal (infrastructural changes to existing urban fabrics) and reveal two basic characteristic for Chinese urban sprawl: a). de-densification; and b). expansion of urbanized areas (urban built-up areas). This proposal aims to use the term “urban sprawl” to consider the reasons behind urban land-use changes and urban pattern transformations on a regional level. It begins with definitions of sprawl in Western and Eastern countries, and follows an analysis of the social, political, and cultural factors of sprawl. Three case studies will focus on three urban centers in China: Beijing, Shanghai, and Guangzhou. Still another component is data analysis with the program SPSS based on related Index for urban sprawl and sustainable development for 15 top urban regions in China during 10 years. This research has explored causes of urban sprawl in China: a). the changing residential preferences of some residents: willing to move out of the core; and b). overcrowded, deteriorated, and old-fashioned structures in central cities becoming targets for demolition in pursuing a new era of modernity, prosperity, and renaissance. Then, this research has pointed out: a). uneven land reform is the key to understand Chinese-style urban sprawl and it is also the necessary condition to the paradox posed by development zones and urbanized villages; b). China’s urban sprawl is driven by both market and government forces; and c). there are a series of new conditions for urban sprawl in China, for example: rising private automobile ownership, rising demand for space and changing residential preference, local public policy, and the real-estate industry. This research intends to provide a comprehensive definition of “urban sprawl” in China, identify the patterns of urban sprawl and growth in three urban regions (Beijing, Shanghai, and Guangzhou), and illustrate the concepts and possible alternative strategies for green urban growth and change in China. Finally, it will offer suggestions on how to effectively control urban sprawl in China, as well as provide a pathway to achieving sustainable development.
Ph.D. in Architecture, July 2012
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Title: MECHANICAL PROPERTIES AND SINTERING MECHANISMS OF POWDER METALLURGY TI6AL4V
Creator: Xu, Xiaoyan
Date: 2013, 2013-05
Description: Titanium has been identified as one of the key materials with a high strength to weight ratio that can reduce the weight of components and...
Show moreTitanium has been identified as one of the key materials with a high strength to weight ratio that can reduce the weight of components and thereby reduce energy consumption. Single press and sinter as a powder metallurgy technique has the potential to provide cost effective components. Armstrong prealloyed Ti6Al4V, HDH prealloyed Ti6Al4V, HDH blended Ti6Al4V powder and their mixtures were pressed and sintered at different conditions. The chemistry, mechanical and microstructural properties have been investigated to establish optimum processing parameters. Sintered parts were sent to Oshkosh Truck to test and compared with aluminum and steel parts. The Titanium and Ti6Al4V parts were successfully applied and tested. All the specimens passed the load test without failures. The sintering mechanisms of Armstrong prealloyed Ti6Al4V powder were investigated. At relative sintered densities of 75% to 90% (around 900°C), surface diffusion cooperate with grain boundary diffusion, which leads to densification of the powder compact. Around 900°C, grain boundary diffusion controls the sintering process. At 1000°C, boundary diffusion made little contribution to the densification of the Ti6Al4V powder compact. Above 900°C and below 91% sintered density, boundary diffusion controls sintering. Lattice diffusion dominates the densification process at higher temperatures (1100°C~1300°C). The sintering of master alloy blended Ti6Al4V powder has been investigated in order to elucidate the mechanism of sintering. Both blended powder compacts and diffusion couples were investigated using backscattered imaging and energy xvi dispersive analysis to determine the phases present and diffusion path on sintering at 1000ºC and 1100ºC. It is shown that transient liquid phase sintering does not occur and the reason for the rapid sintering of this material is due to enhanced diffusion kinetics resulting from a combination of the concentration gradient and stress induced by a phase transformation in the ternary system.
PH.D in Materials Science and Engineering, May 2013
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Title: SUSTAINABLE, CONTROLLED, REACTION SYNTHESIS OF METALLIC WIRES AND STRIPS
Creator: Chen, Xin
Date: 2014, 2014-05
Description: The main purpose of this work is to investigate bi and tri-metallic metal com- binations as initiators which require an ability to have a self...
Show moreThe main purpose of this work is to investigate bi and tri-metallic metal com- binations as initiators which require an ability to have a self-sustaining exothermic reaction. Through the reaction, the initiator should achieve a temperature in excess of 500 C when in contact with a thermally conducting surface. Also the initiator must be in the form of a exible wire or strip of the order of one millimeter radius. There are four phases in my MS research project. First was identifying the potential candidate compounds for exothermic reaction. During this phase, I wrote a program using Mathematicar (Appendix A) to calculate the adiabatic temperature resulting from the reaction of di erent binary or ternary elemental combinations. The calculation took into account the speci c heats and any enthalpies of transformation occurring between room temperature and the adiabatic temperature. Based on the results of this program several suitable compositions were selected from three hun- dred candidates. The second phase was determining a methodology to manufacture selfCpropagating thin strips or wires. We attempted several methods including plate rolling, wire twisting, mechanical coating, chemical coating, and powder metallurgy. We successfully obtained self-propagating thin metal strips and wires using powder metallurgy methods. In the third phase, a transparent reaction box was constructed in order to provide a protective atmosphere (Ar gas) and connect to a data acqui- sition system to obtain the reaction temperature, initiation temperature and video materials of reactions. In the last phase, the reacted samples were characterized using Scanning Electron Microscope (SEM), Backscattered Electron detector (BSE), X-ray Di raction (XRD), Di erential scanning calorimeter (DSC), etc.
M.S. in Mechanical, Materials, and Aerospace Engineering, May 2014
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