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Title: NEOVASCULARIZAnON WITHIN POROUS PEG HYDROGELS
Creator: Chiu, Yu-chieh
Date: 2011-11, 2011-12
Description: Development of engineered tissues of clinically relevant size requires the ability to control vascularization within biomaterial scaffolds....
Show moreDevelopment of engineered tissues of clinically relevant size requires the ability to control vascularization within biomaterial scaffolds. Poly(ethylene glycol) (PEG) hydrogels have been extensively investigated for use as synthetic scaffolds to support engineered tissue formation. The goal of this work described was to develop techniques that can be used to enhance vascularized tissue formation in PEG-based hydrogels. In the first part of the study a technique was developed to generate porous PEG hydrogels using a salt leaching technique. This technique was then used to examine the role of pore size on vascularization and tissue remodeling in porous PEG hydrogel in vitro and in vitro. Both in vitro and in vivo studies showed that vessel invasion was pore size dependent. In addition, a thin layer of inflammatory tissue was observed between PEG hydrogel and blood vessels that formed within the gels. This layer suggested that inflammatory cells, not vascular cells, interacted with the surface of the material. This suggests that peptides covalently incorporated within PEG may not directly interact with endothelial cells (ECs) following implantation. The porous PEG hydrogels were very stable in vitro and in vivo and did not exhibit any signs of degradation. Hydrogels used in tissue engineering need to exhibit controlled degradation. In order to address the stability of PEG hydrogels, porous hydrogels were rendered using degradable PEG-co-(L-Lactic acid) diacrylate PEG-PLLA-DA. This polymer is degraded via hydrolysis of the PLLA chains. The porous PEG-PLLA-DA hydrogels were generated by solvent casting, photopolymerization, and particulate leaching. The influence of polymer conditions on the architecture, degradation, and mechanical properties of the hydrogels were investigated in vitro. The hydrogels were found to exhibit autofluorescence that allowed for the unique ability to nondestructively image hydrogel structure under fully swelled conditions using confocal microscopy. Initial pore size was a function of particulate size and independent of polymer concentration. Interestingly, pore size remained stable though out the study, and was not a function of degradation. In addition, degradation time of porous PEG-LLA-DA hydrogels was influenced by polymer concentration. Compressive modulus was a function of polymer concentration and pore size and decreased during hydrogel degradation. The incorporation of cell adhesion sequences into the hydrogel showed that they can support cell adhesion with morphology varying with pore size. This technique could be used to tailor porous biodegradable scaffolds for tissue engineering applications. In the final portion of this thesis a poly-lysine (PLL) molecule was synthesized in order to allow clustering of adhesion sequences in PEG hydrogels. Clusters of peptide sequences have been shown to enhance cell interactions with substrate surfaces. The sequence was synthesized and purified by high performance liquid chromatography (HPLC) and characterized by mass spectrometry. The side chains of the PLL molecule was used to attach peptide sequences. Cysteine contained within the PLL allowed incorporation into the PEG hydrogel by mixed mode polymerization. Cells were observed to adhere to hydrogels containing the RGD clusters and not to the control gels. The results presented here describe various techniques that can be used to optimize the design of polymer scaffolds for tissue engineering. In addition, the data provide insight into the process of vascularization in porous hydrogels and the influence of synthesis conditions and degradation on properties of porous hydrogels. Future studies should investigate the optimization of these material techniques for control of neovascularization within PEG hydrogels for tissue engineering applications.
Ph.D. in Biomedical Engineering, December 2011
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Title: HOT DUCTILITY BEHAVIOR IN THE CONTINUOUS CASTING OF NIOBIUM-BEARING MICROALLOYED STEELS
Creator: Jansto, Steven George
Date: 2013, 2013-12
Description: Over 200 million tons of Niobium-bearing steels were continuously cast and hot rolled globally in 2012. These Nb-bearing plate, bar and sheet...
Show moreOver 200 million tons of Niobium-bearing steels were continuously cast and hot rolled globally in 2012. These Nb-bearing plate, bar and sheet products are manufactured throughout the world. The melting and casting practices to assure production of crack-free slabs, billets and blooms of high surface quality is presented. Much has been published about the traditional ductility trough associated with higher carbon equivalent steels with and without microalloy additions of Nb, V and/or Ti. The focus has primarily been on the chemistry and optimal composition based upon the literature review. However, the steelmaking and process metallurgy parameters are rarely correlated to the hot ductility behavior. Most studies involve laboratory produced heats, but this research is based upon industrial produced samples.The hot ductility troughs associated with simple carbon-manganese steels can also result in surface and internal quality issues if certain steelmaking and casting parameters are not followed. Although high carbon equivalent steels exhibit inherently lower hot ductility behavior, as measured by percent reduction in area at elevated temperature, these steels still exhibit sufficient ductility to satisfactorily meet the unbending stress and strain gradients existing in the straightening section of most casters. The % Reduction in Area significantly overstates the minimum ductility required for crack-free casting of Nb-bearing steels. The relationship between the steelmaking and caster operation and the resultant slab quality is related through the hot ductility behavior. This global Nb-bearing continuous casting steel research study introduces the strain energy as an improved xxi measure of the hot ductiity behavior. The incidence of cracking is primarily related to the steelmaking and caster process parameters and steel chemistry is secondary. These parameters include the elemental residual chemistry level, superheat variation, transfer ladle temperature stratification, oscillation frequency and stroke, mould flux incompatibility, casting speed fluctuation, and excessive secondary cooling.
PH.D in Materials Science and Engineering, December 2013
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Title: PRICING AND APPLICATION OF ELECTRIC STORAGE
Creator: Zhao, Jialin
Date: 2017, 2017-05
Description: Electric storage provides a vehicle to store power for future use. It contributes to the grids in multiple aspects. For instance, electric...
Show moreElectric storage provides a vehicle to store power for future use. It contributes to the grids in multiple aspects. For instance, electric storage is a more effective approach to provide electricity ancillary services than conventional methods. Additionally, electric storage, especially fast-responding units, allows owners to implement high-frequency power transactions in settings such as the 5-min real-time trading market. Such high-frequency power trades were limited in the past. However, as technology advances, the power markets have evolved. For instance, the California Independent System Operator now supports the 5-min real-time trading and the hourly day-ahead ancillary services bidding. Existing valuation models of electric storage were not designed to accommodate these recent market developments. To fill this gap, I focus on the fast-responding grid-level electric storage that provides both the real-time trading and the day-ahead ancillary services bidding. To evaluate such an asset, I propose a Monte Carlo Simulation-based valuation model. The foundation of my model is simulations of power prices. This study develops a new simulation model of electric prices. It is worth noting that, unlike existing models, my proposed simulation model captures the dependency of the real-time markets on the day-ahead markets. Upon such simulations, this study investigates the pricing and the application of electric storage at a 5-min granularity. Essentially, my model is a Dynamic Programming system with both endogenous variables (i.e., the State-of-Charge of electric storage) and exogenous variables (i.e., power prices). My first numerical example is the valuation of a fictitious 4MWh battery. Similarly, my second example evaluates the application of two units of 2MWh batteries. By comparing these two experiments, I investigate the issues related to battery configurations, such as the impacts of splitting storage capability on the valuation of electric storage.
Ph.D. in Management Science, May 2017
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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: QUANTITATIVE ANALYSIS OF THE EFFECTS OF BIOFUNCTIONAL AND PHYSICAL GRADIENTS ON CELL BEHAVIOR IN POLY (ETHYLENE GLYCOL) DIACRYLATE HYDROGELS
Creator: Turturro, Michael
Date: 2012-10-29, 2012-12
Description: The continued enhancement of tissue engineered scaffolds relies on their ability to stimulate the formation of a stable microvascular network...
Show moreThe continued enhancement of tissue engineered scaffolds relies on their ability to stimulate the formation of a stable microvascular network within the biomaterial. In vivo, the spatial presentation of immobilized extracellular matrix cues and matrix mechanical properties play an important role in directed and guided cell behavior and neovascularization. The overall goals of this thesis are to develop a technique for the generation of gradients of physical properties and incorporated biofunctionality within poly(ethylene glycol) diacrylate (PEGDA) scaffolds and to investigate the effects of these gradients on 3D cell invasion and neovascularization. To this end, a novel photopolymerization technique for generating spatial variations in matrix properties and incorporated biofunctionality within synthetic PEGDA hydrogels, perfusion-based frontal polymerization (PBFP), was developed. This technique relies on the controlled perfusion of a photoinitiator to a reaction chamber containing a precursor solution and results in the propagation of a polymer reaction front that travels through the monomer solution creating a gradient in hydrogel crosslinking. Manipulation of the magnitude of the gradient can be achieved through alterations in the polymerization conditions. Scaffolds with embedded gradients were designed and optimized based on a range of properties shown to support 2D cell adhesion, proliferation, and 3D vascular cell invasion in bulk photopolymerized hydrogels with homogeneous properties. An in vitro model of neovascularization was used to evaluate the effect of these gradients on vascular sprout formation. Sprout invasion in gradient hydrogels occurred bi-directionally with sprout alignment observed in the direction parallel to the gradient while control hydrogels with homogeneous properties resulted in uniform invasion. In PBFP gradient hydrogels, sprout xvi length was found to be twice as long in the direction parallel to the gradient as compared to the perpendicular direction after three weeks in culture. This directionality was found to be more prominent in gradient regions of increased stiffness, crosslinked matrix metalloproteinase (MMP)-sensitive peptide presentation, and immobilized YRGDS concentration. In vivo tissue invasion was shown to be directly related to gradient properties and orientation. Alterations in the magnitude of the gradient in elastic modulus enhanced the directionality of invading vascular sprouts while restricting in vivo tissue invasion.
PH.D in Biomedical Engineering, December 2012
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Title: PSYCHOMETRIC PROPERTIES OF THE CENTER FOR EPIDEMILOGICAL STUDIES DEPRESSION SCALE (CES-D) USED AMONG NATIVE CHINESE INDIVIDUALS WITH SPINAL CORD INJURY
Creator: Xiong, Ying
Date: 2014, 2014-07
Description: Depressive symptoms are highly prevalent among people with Spinal Cord Injury (SCI) and yet there is a lack of consensus over psychometrically...
Show moreDepressive symptoms are highly prevalent among people with Spinal Cord Injury (SCI) and yet there is a lack of consensus over psychometrically sound diagnostic criteria or screening tools for depression. This is particularly true with the SCI population in China. Currently, there is limited information regarding the prevalence of depression, severity, and depressive symptomatology among individuals with SCI in China. CES-D lOis a simple and quick tool to use, and it avoids over-estimating depression due to frequent somatic complaints associated with SCI. To our best knowledge, the CES-D 10 had not been used among the native Chinese population with SCI. The current study used the CES-D 10 to measure depressive symptoms among individuals with SCI in China. The purpose ofthis study was to examine factorial validity, internal consistency, construct validity, and concurrent validity ofCES-D 10 among 260 Chinese individuals with SCI. Results showed an alarmingly high prevalence of depressive symptoms among the sample. Consistent with existing literature and hypotheses, a two-factor structure of CES-D 10 was replicated based on a confirmatory factor analysis. Hierarchical regression analyses showed several important psychosocial constructs such as acceptance of disability, social support, and functional disability were predictors of overall depressive symptoms. Surprisingly, depressive symptoms were not predictive of employment status. The scale showed low internal consistency, and a cultural response bias in which participants are less likely to endorse positively-stated CES-D items among the current sample. Such finding is consistent with past studies among the East Asian population. Limitations and implications ofthe study were discussed.
Ph.D. in Psychology, July 2014
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Title: CAPACITY BOUNDS FOR LARGE SCALE WIRELESS SENSOR NETWORKS
Creator: Tang, Shaojie
Date: 2012-11-20, 2012-12
Description: We study the network capacity of large scale wireless sensor networks under both Gaussian Channel model and Protocol Interference Model. To...
Show moreWe study the network capacity of large scale wireless sensor networks under both Gaussian Channel model and Protocol Interference Model. To study network capacity under gaussian channel model, we assume n wireless nodes {v1, v2, · · · , vn} are randomly or arbitrarily distributed in a square region Ba with side-length a. We randomly choose ns multicast sessions. For each source node vi, we randomly select k points pi,j (1 ≤ j ≤ k) in Ba and the node which is closest to pi,j will serve as a destination node of vi. The per-flow unicast(multicast) capacity is defined as the minimum data rate of all unicast(multicast) sessions in this network. We derive the achievable upper bounds on unicast capacity and a upper bound(partial achievable) on multicast capacity of the wireless networks under and Gaussian Channel model. We found that the unicast(multicast) capacity for wireless networks under both two models has three regimes. Under protocol interference model, we assume that n wireless nodes are randomly deployed in a square region with side-length a and all nodes have the uniform transmission range r and uniform interference range R > r. We further assume that each wireless node can transmit/receive at W bits/second over a common wireless channel. For each node vi, we randomly pick k − 1 nodes from the other n − 1 nodes as the receivers of the multicast session rooted at node vi. The aggregated multicast capacity is defined as the total data rate of all multicast sessions in the network. In this work we derive matching asymptotic upper bounds and lower bounds on multicast capacity of large scale random wireless networks under protocol interference model.
PH.D in Computer Science, December 2012
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Title: EMPIRICALLY KEYING PERSONALITY MEASURES TO MITIGATE FAKING EFFECTS AND IMPROVE VALIDITY: A MONTE CARLO INVESTIGATION
Creator: Tawney, Mark Ward
Date: 2012-12-05, 2012-12
Description: Personality-type measures should be viable tools to use for selection. They have incremental validity over cognitive measures and they add...
Show morePersonality-type measures should be viable tools to use for selection. They have incremental validity over cognitive measures and they add this incremental validity while decreasing adverse impact (Hough, 1998; Ones, Viswesvaran & Schmidt, 1993; Ones & Viswesvaran, 1998a). However, personality measures are susceptible to faking; individual’s instructed to fake on personality measures are able to increase their scores (Barrick & Mount, 1996; Ellingson, Sackett & Hough, 1999; Hough, Eaton, Dunnette, Kamp, & McCloy, 1990). Further, personality measures often reveal less than optimal validity estimates as research continually finds meta-analytic coefficients near .2 (e.g., Morgeson, Campion, Dipboye, Hollenbeck, Murphy, & Schmitt, 2007). Some researchers have suggested that these two problems are linked as faking on personality measure may reduce their ability to predict job performance (e.g., Tett & Christansen, 2007). Empirically keyed instruments traditionally enhance prediction and have been found to mitigate the effects of faking (Kluger, Reilly & Russell, 1991; Scott & Sinar, 2011). Recently suggested as a means to key to personality measures (e.g., Tawney & Mead, In Prep), this dissertation further investigates empirical keying methods as a means to both mitigate faking effects and as a means to increase validity of personality-type measures. A Monte Carlo methodology is used due to the difficulties in obtaining accurate measures of faking. As such, this dissertation investigates faking issues under controlled and known parameters, allowing for more robust conclusions as compared to prior faking research.
PH.D in Psychology, December 2012
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Title: TOWARDS THE EXACT CALCULATIONS OF THE FREE ENERGY FOR ENTANGLED SEMIFLEXIBLE POLYMER CHAIN
Creator: Pilyugina, Ekaterina
Date: 2015, 2015-05
Description: This work consists of two separate projects unified by the idea to extend the Discrete Slip-Link Model, which has been being successfully...
Show moreThis work consists of two separate projects unified by the idea to extend the Discrete Slip-Link Model, which has been being successfully developed in this group to predict rheological behavior of entangled flexible polymers, to new applications. The first project was dedicated to application of the Discrete Slip-Link Model to dielectric relaxation in order to simultaneously predict linear rheology and dielectric relaxation experiments of entangled polyisoprenes. Linear monodisperse, linear bidisperse and star-branched monodisperse systems were studied. It was found that all circumstances save one are well described. Namely, dilute long chains in a sea of short chains can be predicted rheologically, but dielectric relaxation data show a reduction in the relaxation time of long chains greater than that predicted by either the DSM or the expected Rouse motion. The second project was focused on the derivation of the exact free energy expression for semiflexible chains in the presence of entanglements in order to implement the DSM for semiflexible polymers. The special cases of chains with one, two and three strands are examined. An additional implementation of obtained results for one and two strands to buckling instability was performed. It is believed that in two dimensional case the critical buckling force is increased by thermal fluctuations in comparison to classical Euler buckling. However, how the critical buckling force is influenced by thermal fluctuations in three dimensions remains unclear. Some research groups calculate the critical buckling force approximately and conclude that, in opposite to 2D case, in 3D the force is decreased by thermal fluctuations. In this work the critical buckling force for semiflexible chain under compression was calculated exactly. It was shown that thermal fluctuations significantly increase the critical force over classical Euler buckling force in both two and three dimensions.
Ph.D. in Chemical Engineering, May 2015
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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: INJECTION LOCKING BASED ULTRA LOW POWER RADIO FREQUENCY INTEGRATED CIRCUITS
Creator: Zhu, Qiang
Date: 2012-05-31, 2012-07
Description: Recent advances in radio frequency integrated circuit (RFIC) technology enable various innovative and versatile applications through ultra-low...
Show moreRecent advances in radio frequency integrated circuit (RFIC) technology enable various innovative and versatile applications through ultra-low-power wireless link such as mesh sensor network, personal area network (PAN) and semi-active RFID. This thesis introduces energy efficient demodulator and transceiver design for wireless communications. At the receiver front end, an ultra-low-power BPSK demodulator based on injection locked oscillators (ILOs) is introduced. Two second harmonic ILOs are employed to convert BPSK signals to ASK signals, which are then demodulated by an envelope detector to baseband. For sub-GHz applications, the ILOs are implemented using ring oscillators to allow compact chip area and ultra-low power dissipation. Bit error rate (BER) analysis of this demodulator indicates erroneous polarity flipping of demodulated bits due to phase noise of the ILO. The prototype chip is fabricated in a 65nm CMOS technology that consumes 228μW of power and occupies 0.014mm2 of die area. Measurement results reveal the demodulation of 750MHz 5Mb/s differential BPSK signal with a sensitivity of -43dBm. Theoretical BER analysis has been verified with erroneous flipping observed in the measurement and its probability close to the prediction. Then, an innovative injecting locking based transceiver architecture for ultra low power operation is proposed. It applied the ILO based BPSK demodulator at the receiver side. The oscillating signal at one receiver ILO also injects to another transmitter ILO for accurate carrier generation. Thus local frequency synthesis circuit which consumes considerable portion of power in traditional transceiver is not required. This design is implemented in a 45nm CMOS SOI technology. Measurement results indicate that the transceiver achieves downlink demodulation of -35dBm BPSK signal at 5Mb/s data rate and uplink transmission of -23dBm ASK signal at 1Mb/s data rate with 0.93mA current consumption from 1V power supply.
Ph.D. in Electrical Engineering, July 2012
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Title: A MULTI-CURVE LIBOR MARKET MODEL WITH UNCERTAINTIES DESCRIBED BY RANDOM FIELDS
Creator: Xu, Shengqiang
Date: 2012-12-19, 2012-12
Description: The LIBOR (London Interbank Offered Rate) market model has been widely used as an industry standard model for interest rates modeling and...
Show moreThe LIBOR (London Interbank Offered Rate) market model has been widely used as an industry standard model for interest rates modeling and interest rate derivatives pricing. In this thesis, a multi-curve LIBOR market model, with uncertainty described by random fields, is proposed and investigated. This new model is thus called a multi-curve random fields LIBOR market model (MRFLMM). First, the LIBOR market model is reviewed and the closed-form formulas for pricing caplets and swaptions are provided. It is extended to the case when the uncertainty terms are modeled as random fields and consequently the closed-form formulas for pricing caplets and swaptions are derived. This is a new model called the random fields LIBOR market model (RFLMM). Second, local volatility models and stochastic volatility models are combined with the RFLMM to explain the volatility skews or smiles observed in market. Closedform volatility formulas are derived via the lognormal mixture model in local volatility case, while the approximation scheme for the stochastic volatility case is obtained by a stochastic Taylor expansion method. Moreover, the above work is further extended to a multi-curve framework, where the curves for generating future forward rates and the curve for discounting cash flows are modeled distinctly but jointly. This multi-curve methodology is recently introduced lately by some pioneers to explain the inconsistency of interest rates after the 2008 credit crunch. Both LIBOR market model and RFLMM mentioned above can be categorized as models in singe-curve framework. Third, analogous to the single-curve framework, the multi-curve random fields LIBOR market model is derived and caplets and swaptions are priced with closedform formulas that can be reduced to exactly the Black’s formulas. This model is called a multi-curve random fields LIBOR market model (MRFLMM). Meanwhile, xii local volatility and stochastic volatility models are also combined with the multi-curve LIBOR market model to explain the volatility skews and smiles in the market. Fourth, the calibration of the above models is considered. Taking two-curve setting as an example, four different models, single-curve LIBOR market model, single-curve RFLMM, two-curve LIBOR market model and two-curve RFLMM are compared. The calibration is based on the spot market data on one trading day. The four models are calibrated to European cap volatility surface and swaption volatilities, given the specified parameterized form of correlation and instantaneous volatility. The calibration results show that the random fields models capture the volatility smiles better than non-random fields models and has less pricing error. Moreover, multi-curve models perform better than single-curve models, especially during/after credit crunch. Finally, the estimation of these four models, including pricing and hedging performance, is considered. The estimation uses time series of forward rates in market. Given a time series of term structure, the parameters of the four models are estimated using unscented Kalman filter (UKF). The results show that the random fields models have better estimation results than non-random fields models, with more accurate in-sample and out-sample pricing and better hedging performance. The multi-curve models also over-perform the single-curve models. In addition, it is shown theoretically and empirically that the random fields models have advantages that it is unnecessary to determine the number of factors in advance and not needed to re-calibrate. The multi-curve random fields LIBOR market model has the advantages of both multi-curve framework and random fields setting.
PH.D in Applied Mathematics, December 2012
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Title: AUTOMATED PROGRESS CONTROL USING LASER SCANNING TECHNOLOGY
Creator: Zhang, Chengyi
Date: 2013, 2013-05
Description: Assessing progress in different construction activities at the end of every payment period is time consuming and requires specialized...
Show moreAssessing progress in different construction activities at the end of every payment period is time consuming and requires specialized personnel employed by the contractor and the owner. Automatic progress control that requires a minimum amount of human involvement could reduce the time spent on this activity, reduce the number of personnel used, reduce the cost involved, reduce disagreements between contractor and owner, and add to the overall efficiency of project management. Attempts have been made in the past to resolve this issue using image processing and other techniques but the results have not been satisfactory. A new attempt was made to set up a system that can assess progress control with minimum human input and the results are presented in this paper. The experiment made use of laser scanning technology and was conducted both in laboratory conditions and construction sites. The initial results from laboratory condition appear to be promising but there are still obstacles to surmount. The system is robust and accurate in laboratory conditions and constitutes proof of concept. Improvements are made to accelerate the registration process of multiple scans, to reduce the noise data, to recognize objects of irregular shape, and to assess the practicality and economic feasibility of such a system when applying this system in real construction sites. Keywords: Construction scheduling, progress control, laser scanning
PH.D in Civil Engineering, May 2013
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Title: SCALABLE RESOURCE MANAGEMENT SYSTEM SOFTWARE FOR EXTREMESCALE DISTRIBUTED SYSTEMS
Creator: Wang, Ke
Date: 2015, 2015-07
Description: Distributed systems are growing exponentially in the computing capacity. On the high-performance computing (HPC) side, supercomputers are...
Show moreDistributed systems are growing exponentially in the computing capacity. On the high-performance computing (HPC) side, supercomputers are predicted to reach exascale with billion-way parallelism around the end of this decade. Scientific applications running on supercomputers are becoming more diverse, including traditional large-scale HPC jobs, small-scale HPC ensemble runs, and fine-grained many-task computing (MTC) workloads. Similar challenges are cropping up in cloud computing as data-centers host ever growing larger number of servers exceeding many top HPC systems in production today. The applications commonly found in the cloud are ushering in the era of big data, resulting in billions of tasks that involve processing increasingly large amount of data. However, the resource management system (RMS) software of distributed systems is still designed around the decades-old centralized paradigm, which is far from satisfying the ever-growing needs of performance and scalability towards extreme scales, due to the limited capacity of a centralized server. This huge gap between the processing capacity and the performance needs has driven us to develop next-generation RMSs that are magnitudes more scalable. In this dissertation, we first devise a general system software taxonomy to explore the design choices of system software, and propose that key-value stores could serve as a building block. We then design distributed RMS on top of key-value stores. We propose a fully distributed architecture and a data-aware work stealing technique for the MTC resource management, and develop the SimMatrix simulator to explore the distributed designs, which informs the real implementation of the MATRIX task execution framework. We also propose a partition-based architecture and resource sharing techniques for the HPC resource management, and implement them by building the Slurm++ real workload manager and the SimSlurm++ simulator. We study the distributed designs through real systems up to thousands of nodes, and through simulations up to millions of nodes. Results show that the distributed paradigm has significant advantages over centralized one. We envision that the contributions of this dissertation will be both evolutionary and revolutionary to the extreme-scale computing community, and will lead to a plethora of following research work and innovations towards tomorrow’s extremescale systems.
Ph.D. in Computer Science, July 2015
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Title: CO2 CAPTURE AND HYDROGEN PRODUCTION IN SORBENT ENHANCED WATER-GAS SHIFT (SEWGS) PROCESS WITH REGENERABLE SOLID SORBENT
Creator: Zarghami Khanehsar, Shahin
Date: 2015, 2015-07
Description: Carbon dioxide emission from fossil fuel combustion and its impact on global warming is one of the most critical environmental issues nowadays...
Show moreCarbon dioxide emission from fossil fuel combustion and its impact on global warming is one of the most critical environmental issues nowadays. Coal as a main source of produce energy is the most CO2-intensive fossil fuel. Advanced power generation processes that use gasification technology, such as Integrated Gasification Combined Cycle (IGCC), which offer higher efficiency, are among the leading contenders for power generation in the 21st century. In an IGCC process, because of high pressure, carbon dioxide in the fuel gas is at higher concentration, which can be captured and sequestered at lower costs. Utilization of regenerable MgO-based sorbents has been shown to be an effective method for capturing CO2 from gasification-based processes at elevated temperatures and pressures (i.e. p > 20 atm and 330° < T < 450°C). Low cost MgO based sorbent can be prepared through modification of natural dolomite. The reactivity of the sorbent in carbonation/regeneration cycles has a significant impact on the economics of the proposed regenerable process. Although the sorbent can be regenerated in successive cycles, the sorbent reactivity and capacity gradually decline during the cyclic process. Therefore, it is crucial to develop a better understanding on the role of the key parameters affecting the reactivity of the sorbent going through the cyclic carbonation/regeneration process. In this work, a systematic study on the sorbent preparation parameters (i.e., calcination temperature, calcination duration, calcination temperature ramp, potassium concentration, impregnation duration, drying temperature, re-calcination temperature, and re-calcination duration) was conducted to understand the effect of each parameter on the overall capacity and reactivity of the sorbent. The concentration of potassium additive (as carbonation reaction promoter) has the most significant effect on the reactivity of the sorbent and the optimum K/Mg molar ratio appears to be in the range of 0.1-0.16. The reactivity of the sorbent toward carbon dioxide at various operating conditions (i.e. temperature, CO2 concentration and steam concentration) was experimentally evaluated. The presence of steam significantly improves the reactivity of the sorbent which is attributed to formation of more favorable pore structure as well as the existence of a parallel carbonation reaction pathway involving the formation of a transient MgO.H2O* compound. The optimum carbonation reaction temperature in the presence of steam is around 380˚C. The effect of cycling on CO2 capture capacity of MgO-based sorbent was also experimentally investigated in this work. Series of carbonation/regeneration cycles (up to 25) have been carried out in a dispersed bed reactor to determine the effect of various variables on long term durability of the sorbent. The gradual loss of CO2 sorption capacity appears to be mainly due to loss potassium (a carbonation reaction promoter) in the cyclic process. Durability of the sorbents improves in the presence of steam, which is likely due to the favorable changes in the pore structure of the sorbents. A kinetic model was developed to fit the reactivity curves obtained from the dispersed bed tests at different operating conditions which was needed to predict the sorbent/catalyst performance in the regenerative process. Model parameters were defined and discussed for each of the operating conditions, as well as dispersed bed cyclic tests. Furthermore, the thermal behavior and the kinetics of partial decomposition of dolomite were studied in a dispersed-bed reactor to improve the reactivity of the sorbent. The microstructure and the nature of the solid products were found to be strongly dependent on the CO2 partial pressure near the reacting interface and on the decomposition temperature. A significant increase in the rate of the dolomite decomposition reaction was found in the presence of steam. Steam improves the kinetics of decomposition, modifies the radial distribution of the pores; and improves the connectivity of the pores inside the dolomite particles, which decreases the diffusion resistance of produced carbon dioxide inside the particle. A shrinking core model with variable product layer diffusivity was used to fit the experimental data and determine the kinetic parameters of the dolomite decomposition reaction. The results indicate that transport of CO2 across the reacting interface in the porous particle was the main limiting factor in the decomposition reaction at the experimental conditions investigated. A lab-scaled high-pressure/high-temperature packed-bed reactor was utilized to evaluate the performance of the sorbent in simultaneous water-gas shift reaction and sorbent carbonation environment. It was shown that the CO2 in the coal gas can be removed by regenerable MgO-based sorbents at temperatures around 350°C, and the CO2 removal can shift WGS reaction to enhance hydrogen production. Therefore, Sorbent Enhanced Water-Gas-Shift (SEWGS) can result in much higher hydrogen production without lowering the temperature, leading to higher overall process efficiency.
Ph.D. in Chemical Engineering, July 2015
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Title: INCORPORATING REACTIVE POWER MARKET INTO THE DAY-AHEAD ELECTRICITY MARKET
Creator: Al Ghamdi, Mohammed
Date: 2012-05-29, 2012-07
Description: The research work presented in this thesis proposes the incorporation of the reactive power market into the day-ahead electricity market in...
Show moreThe research work presented in this thesis proposes the incorporation of the reactive power market into the day-ahead electricity market in order to compensate generation companies (GENCOs) and independent power producers (IPPs) for providing any additional reactive power support, which varies on an hourly basis based on the load demand, transmission network configuration, and any contingencies that might occur. This proposal would minimize the total payment burden on the independent system operator (ISO), which is related to the reactive power dispatch. The proposed model achieves the main objective of an ISO in a competitive electricity market, which is to provide the required reactive power support from generators at minimum cost while ensuring the secure operation of the power system. In this research, the reactive power price is the bidding-based price that is submitted by the GENCOs and IPPs to the ISOs during the day-ahead market. The proposal takes into the account both the technical and economic aspects associated with the active power and reactive power dispatch in the context of the new operating paradigms in competitive electricity markets. In this research, the Security Constrained Unit Commitment (SCUC) based on AC power flow modeling is considered as the drive engine for clearing the day-ahead electricity market based on the amount of information provided by the market participants. This proposed framework would provide appropriate reactive power support from service providers at minimum cost, while ensuring the secure and reliable operation of the electrical power system. In the research, the PQ capability curves of the generating units are modeled to ensure the practically of the SCUC solutions that are obtained. This proposal would be an essential step toward a fair electricity market while increasing the security of the power system and reducing transmission congestions. Also, it would pave the road for various renewable energy resources since the penetration of renewable energy resources would impact the commitment of the generating units. This would impact the available reactive power reserve margin and security of the network. In addition, incorporating the reactive power market into the day-ahead market would provide a clear signal for optimal private investment in the reactive power capacity. The framework that has been developed is general in nature and can be used for any electricity market structure.
Ph.D. in Electrical Engineering, July 2012
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Title: INVESTIGATION OF NIOBIUM SURFACE STRUCTURE AND COMPOSITION FOR IMPROVEMENT OF SUPERCONDUCTING RADIO-FREQUENCY CAVITIES
Creator: Trenikhina, Yulia
Date: 2014, 2014-12
Description: Nano-scale investigation of intrinsic properties of niobium near-surface is a key to control performance of niobium superconducting radio...
Show moreNano-scale investigation of intrinsic properties of niobium near-surface is a key to control performance of niobium superconducting radio-frequency cavities. Mechanisms responsible for the performance limitations and their empirical remedies needs to be justified in order to reproducibly control fabrication of SRF cavities with desired characteristics. The high field Q-slope and mechanism behind its cure (120◦C mild vacuum bake) were investigated by comparison of the samples cut out of the cavities with high and low dissipation regions. Material evolution during mild field Q-slope nitrogen treatment was characterized using the coupon samples as well as samples cut out of nitrogen treated cavity. Evaluation of niobium near-surface state after some typical and novel cavity treatments was accomplished. Various TEM techniques, SEM, XPS, AES, XRD were used for the structural and chemical characterization of niobium near-surface. Combination of thermometry and structural temperature-dependent comparison of the cavity cutouts with different dissipation characteristics revealed precipitation of niobium hydrides to be the reason for medium and high field Q-slopes. Step-by-step effect of the nitrogen treatment processing on niobium surface was studied by analytical and structural characterization of the cavity cutout and niobium samples, which were subject to the treatment. Low concentration nitrogen doping is proposed to explain the benefit of nitrogen treatment. Chemical characterization of niobium samples before and after various surface processing (Electropolishing (EP), 800◦C bake, hydrofluoric acid (HF) rinsing) showed the differences that can help to reveal the microscopic effects behind these treatments as well as possible sources of surface contamination.
Ph.D. in Physics, December 2014
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Title: EXPLOITING NETWORK CODING IN DIFFERENT WIRELESS NETWORKS
Creator: Guo, Bin
Date: 2012-07-06, 2012-07
Description: Wireless communication networks have been incorporated into our daily life and provide convenience anytime and anywhere. However, the wireless...
Show moreWireless communication networks have been incorporated into our daily life and provide convenience anytime and anywhere. However, the wireless medium is unreliable and unpredictable. Current wireless networks suffer from low throughput, low reliability, etc. Network coding, an alternative approach, has attracted more interests and has emerged as an important technology in wireless networks. It can provide significant potential throughput improvements and a high degree of robustness. This dissertation is built on the theory of network coding. In this dissertation, different network coding protocols are designed in varied wireless networks. The first part of this dissertation proposes a novel coding-ware routing protocol in wireless mesh networks. In particular, a generalized coding condition is formally established to identify the coding opportunities. Based on general coding conditions analysis, a novel routing metric FORM (Free-ride Optimal Routing Metric) and the corresponding routing protocol are developed with the objective to exploit the coding opportunities and maximize the benefit of “free-ride” in order to reduce the total number of transmissions and consequently to increase the network throughput. The results show the proposed protocol achieves significant throughput gain than existing approaches. The second part of this dissertation exploits network coding in wireless cooperative networks. Firstly, a Decode-and-Forward Network Coded (DFNC) protocol is proposed for multi-user cooperative communication system. In particular, DFNC develops an efficient construction method for coding coefficients and a novel decoding algorithm that combines network coding and channel coding. DFNC exploits both temporal and spatial diversities through multiple channels by allowing all the users to generate redundant network-coded packets in a distributed manner and it helps fully explore the redundancy provided by network coding to realize error correction. Theoretical analysis and simulation results demonstrate that DFNC outperforms other transmission schemes in terms of Symbol Error Rate (SER) and achieves higher diversity order. Secondly, the idea of DFNC is extended and Modified-DFNC (M-DFNC) is introduced for a more practical scenario: not all the users will be able to dedicate their resources to provide assistance for others. The throughput analysis shows that M-DFNC outperforms the conventional cooperative protocol in the low-SNR regime and it implies that an adaptive cooperation system should be adopted to optimize the performance. The simulation results validate the theoretical analysis.
Ph.D. in Electrical Engineering, July 2012
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Title: SUSTAINABLE MULTILINGUAL COMMUNICATION: MANAGING MULTILINGUAL CONTENT USING FREE AND OPEN SOURCE CONTENT MANAGEMENT SYSTEMS
Creator: Kelsey, Todd
Date: 2011-05-03, 2011-05
Description: Multilingual content management systems, combined with streamlined processes and inexpensive organizational tools, make it possible for...
Show moreMultilingual content management systems, combined with streamlined processes and inexpensive organizational tools, make it possible for educators, non-profit entities and individuals with limited resources to develop sustainable and accessible multilingual Web sites. The research included a review of what’s been done in the theory and practice of designing Web sites for multilingual audiences. On the basis of that review, a series of sustainable multilingual Web sites were created, and a series of approaches and systems were tested, including MediaWiki, Plone, Drupal, Joomla, PHPMyFAQ, Blogger, Google Docs and Google Sites. There was also a case study on “Social CMS”, which refers to emergent social networks such as Facebook. The case studies are reported on, and conclude with high-level recommendations that form a roadmap for sustainable multilingual Web site development.
Ph.D. in Technical Communication, May 2011
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Title: THERMAL RESISTANCE OF SALMONELLA ENTERICA AND ESCHERICHIA COLI 0157:H7 IN PEANUT BUTTER
Creator: He, Yingshu
Date: 2014, 2014-05
Description: Salmonella enterica is a frequent food contaminant and the leading cause of foodborne bacterial illnesses in the United States. Our study...
Show moreSalmonella enterica is a frequent food contaminant and the leading cause of foodborne bacterial illnesses in the United States. Our study demonstrated that a 5-strain S. enterica cocktail displayed increased heat resistance in peanut butter of low water activity (aw). Significant differences (P < 0.05) were found between the survival rates of Salmonella enterica and Escherichia coli O157:H7 in peanut butter with different formulations and water activity. High carbohydrate content in peanut butter and low incubation temperature resulted in higher levels of bacterial survival during storage but lower levels of bacterial resistance to heat treatment. Furthermore, we also compared the relative heat resistance of three individual strains of S. enterica representing serotypes Typhimurium, Enteritidis and Tennessee and the 3-strain cocktail treated at both 90oC and 126oC in two different peanut butter formulations with varied fat and carbohydrate contents and adjusted water activities (aw from 0.2 to 0.8). When treated at 90oC, increased water activity in peanut butter significantly (P < 0.05) reduced the heat resistance of desiccation-stressed S. enterica cells. Differences in heat resistance were also detected among the three S. enterica serotypes and between the two peanut butter formulations. When treated at 126oC, the differences in bacterial heat resistance among serotypes and adjusted water activities were less notable (P > 0.05). Based on the Weibull model, an average of 52 to 132 min was required to achieve a 5-log reduction of the 3-strain cocktail at 90oC in peanut butter with an aw of 0.2. When aw was increased to 0.6, to achieve the same 5-log reduction required only 23-27 min. At aw of 0.8, S. enterica could be completely killed in less than 10 min in peanut butter with a fat content of 48.49%. Using scanning electron microscopy, we observed minor morphological changes xiii of S. enterica cells during desiccation and rehydration processes in peanut oil, which was used as a surrogate for peanut putter. Results from this study collectively suggest that water activity plays a critical role in determining S. enterica heat resistance in peanut butter. The variability that exists among the heat resistance of different S. enterica serotypes in different peanut butter formulations should also be taken into consideration for developing and validating effective intervention and mitigation strategies in peanut butter production.
PH.D in Biology, May 2014
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