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Title: THE PARADOX OF COMMUNICATION TECHNOLOGY IN THE WORK-FAMILY INTERFACE
Creator: Ishaya, Nahren M.
Date: 2018, 2018-05
Description: The aim of the present study was to investigate the “double-edged sword” nature of communication technology in its impact on the work-family...
Show moreThe aim of the present study was to investigate the “double-edged sword” nature of communication technology in its impact on the work-family interface. Communication technology has many wonderful advantages, one of which is the flexibility that it provides employees with where and when work is completed. The flipside, though, is that communication technology allows employees to be available and accessible at all times. The purpose of this study was to assess the impact of (1) accessibility and availability through communication technology; and (2) flexibility through communication technology, on the experience of work-to-family conflict, family-to-work conflict, and work-family balance. The study utilized Conservation of Resources theory and Job-Demand Control model as its basis for examining how the relationship between work and family demands and work-family interface outcomes are impacted by the two communication technology variables of interest in this study. Qualtrics Panels were used to recruit 405 working adults in the United States across various industries to complete an online survey. To help address single source bias, employees were asked to invite their spouse/partner to complete a survey to assess levels of work-family interface of the employee from the spouse/partner perspective. Hierarchical moderated regression analyses were used to test the hypotheses. The results indicated that employees who perceive that communication technology provided greater flexibility in the work and family domains experienced less work-to-family conflict, and family-to-work conflict, respectively. Further, employees who perceived that greater expectations to be available and accessible to others in their work and family domains experienced greater work-to-family conflict and family-to-work conflict, respectively. Accessibility and availability expectations exacerbated the association between demands and work-to-family conflict in both the work and family domains. Communication technology flexibility was found to buffer the effect of family overload in the experience of family-to-work conflict. The theoretical and practical implications of these findings and potential directions for future research are discussed.
Ph.D. in Psychology, May 2018
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Title: vVIENER-HOPF FACTORIZATION FOR TIME-INHOMOGENEOUS MARKOV CHAINS AND STATISTICAL INFERENCE FOR STOCHASTIC PARTIAL DIFFERENTIAL EQUATIONS
Creator: Huang, Yicong
Date: 2018, 2018-05
Description: The thesis consists of two major parts, and it contributes to two topics in stochastic analysis – Wiener-Hopf factorization (WHf) for Markov...
Show moreThe thesis consists of two major parts, and it contributes to two topics in stochastic analysis – Wiener-Hopf factorization (WHf) for Markov chains and statistical inference for Stochastic Partial Differential Equations (SPDEs). The first part deals with Wiener-Hopf factorization for finite state time inhomogeneous Markov chains. To the best of our knowledge, this study is the first attempt to investigate the WHf for the time-inhomogeneous Markov chains. In this work we only deal with a special class of time-inhomogeneous Markovian generators, namely piece-wise constant, which allows to derive the corresponding WHf by using an appropriately tailored randomization technique. Besides the mathematical importance of the WHf methodology, there is also an important computational aspect: it allows for efficient computation of important functionals of Markov chains. In this work, we also provide an efficient algorithm to compute the quantities in the Wiener-Hopf factorization for the time-inhomogeneous Markov chains. Finally, we provide a comparison (based on numerical simulations) between our algorithm and the brute-force Monte Carlo simulations. The second part is dedicated to statistical inference for Stochastic Partial Differential Equations (SPDEs). First, we study the problem of estimating the drift/viscosity coefficient for a large class of linear, parabolic SPDEs driven by an additive space-time noise. We propose a new class of estimators, called trajectory fitting estimators (TFEs). The estimators are constructed by fitting the observed trajectory with an artificial one, and can be viewed as an analog to the classical least squares estimators from the time-series analysis. As in the existing literature on statistical inference for SPDEs, we take a spectral approach, and assume that we observe the first N Fourier modes of the solution, and we study the consistency and the asymptotic normality of the TFE, as N ₀₀. Next we consider a parameter estimation problem for one dimensional stochastic heat equation, when data is sampled discretely in time or spatial component. We establish some general results on derivation of consistent and asymptotically normal estimates based on computation of the p-variations of stochastic processes and their smooth perturbations. We apply these results to the considered SPDEs, by using some convenient representations of the solutions. For some equations such representations were ready available, while for others classes of SPDEs we derived the needed representations along with their statistical asymptotic properties. We prove that the real valued parameter next to the Laplacian, and the positive parameter in front of the noise can be consistently estimated by observing the solution at a fixed time and on a discrete spatial grid, or at a fixed space point and at discrete time instances of a finite interval, assuming that the mesh size goes to zero.
Ph.D. in Applied Mathematics, May 2018
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Title: EXPANDING THE HEP FRONTIER WITH BOOSTED B-TAGS AND THE QCD POWER SPECTRUM
Creator: Pedersen, Keith
Date: 2018, 2018-05
Description: As particle physics continues to expand into the high-energy and highluminosity frontiers, it is encountering event topologies with extreme...
Show moreAs particle physics continues to expand into the high-energy and highluminosity frontiers, it is encountering event topologies with extreme boosts and intense pileup. This creates unique challenges that limit our ability to use QCD jets to find new physics and conduct precision tests of the standard model. In this thesis, I present two tools that greatly expand our ability to use jets for these important purposes: (i) The μx boosted-bottom jet tag, whose O(100) signal to background ratio does not falter as jet pT exceeds 1TeV, and which is robust to pileup due to its foundation in boosted kinematics. (ii) Power jets, the first stage in a larger program to harness the power spectrum of QCD radiation to better utilize the vast amount of information collected about each collider event. Using the full power spectrum of a detected event, the power jets framework not only provides an accurate and precise recovery of jet kinematics, but also naturally facilitates a global fit to pileup intensity (rather than a local subtraction of pileup energy, which inadvertently strips soft QCD that belongs to the hard scatter).
Ph.D. in Physics, May 2018
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Title: ON THE LIST COLORING PROBLEM AND ITS EQUITABLE VARIANTS
Creator: Mudrock, Jeffrey Allen
Date: 2018, 2018-05
Description: In this thesis we study list coloring which was introduced independently by Vizing and Erd˝os, Rubin, and Taylor in the 1970’s. Suppose we...
Show moreIn this thesis we study list coloring which was introduced independently by Vizing and Erd˝os, Rubin, and Taylor in the 1970’s. Suppose we associate a list assignment L with a graph G which assigns a list, L(v), of colors to each v 2 V (G). A proper L-coloring of G, f, is a proper coloring such that f(v) 2 L(v) for each v 2 V (G). The list chromatic number of G, "`(G), is the minimum k such that G has a proper L-coloring whenever L is a list assignment satisfying |L(v)| ' k for each v 2 V (G). A graph G is said to be chromatic-choosable if "`(G) = "(G). The list chromatic number of the Cartesian product of graphs is not well understood. The best result is by Borowiecki, Jendrol, Kr´al, and Miˇskuf (2006) who proved that the list chromatic number of the Cartesian product of two graphs can be bounded in terms of the list chromatic number and the coloring number of the factors. In Chapter 2, we use the Alon-Tarsi Theorem and an extension of it discovered by Schauz in 2010 to find improved bounds on the list chromatic number and paint number (i.e. online list chromatic number) of the Cartesian product of an odd cycle or complete graph with a traceable graph. We also identify certain Cartesian products as chromatic-choosable. In Chapter 3, we generalize the notion of strong critical graphs, introduced by Stiebitz, Tuza, and Voigt in 2008, to strong k-chromatic-choosable graphs, and we show that it gives a strictly larger family of graphs that includes odd cycles, cliques, the join of a clique and any strongly chromatic-choosable graph, and many more families of graphs. We prove sharp bounds on the list chromatic number of certain Cartesian products where one factor is a strong k-chromatic-choosable graph satisfying an edge bound. Our proofs rely on the notion of unique-choosability as a sufficient condition for list colorability and the list color function which is a list analogue of the chromatic polynomial.In Chapter 4, we study a list analogue of equitable coloring introduced by Kostochka, Pelsmajer, and West in 2003. A graph G is said to be equitably kchoosable if it has a proper L-coloring that uses no color more than d|V (G)|/ke times whenever |L(v)| = k for each v 2 V (G). Generalizing a conjecture of Fu (1994) on total equitable coloring, we conjecture that for any simple graph G, its total graph, T(G), is equitably k-choosable whenever k ' max{"`(T(G)),"(G) + 2}. We prove this conjecture for all graphs satisfying "(G)  2 while also studying the related question of the equitable choosability of powers of paths and cycles. In Chapter 5, we introduce a new list analogue of equitable coloring: proportional choosability. For this new notion, the number of times a color is used must be proportional to the number of lists in which the color appears. Proportional kchoosability implies both equitable k-choosability and equitable k-colorability. Also,the graph property of being proportionally k-choosable is monotone, and if a graph is proportionally k-choosable, it must be proportionally (k +1)-choosable. We study the proportional choosability of graphs with small order and disconnected graphs, and we completely characterize proportionally 2-choosable graphs.
Ph.D. in Applied Mathematics, May 2018
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Title: SINTER B0NDING TITANIUM POWDER COMPONENTS: AN UNCONVENTIONAL ADDITIVE MANUFACTURING APPROACH
Creator: Montonera, Darrell R
Date: 2018, 2018-05
Description: Titanium and its alloys are desirable for many applications. The cost of producing titanium parts that also have needed microstructure for a...
Show moreTitanium and its alloys are desirable for many applications. The cost of producing titanium parts that also have needed microstructure for a given application limit where titanium is used. Methods of reducing the cost of titanium parts have been to use powder metallurgy processing routes. However, not all powder processing routes are cost effective, as additive manufacturing and powder injection molding processes are costly and require expensive spherical powder. Cheaper processing Press and Sinter utilizes cheaper non-spherical powder. Powder titanium components made through Press and Sinter have complexity, size, and geometrical constraints and have detrimental mechanical properties unless further post processing is done. To utilize the simple geometries from Press and Sinter, pressed powder components are bonded to examine the possibility of creating higher complexity parts. To achieve this, the dimensional sintering behavior of powders were quanti- ed using dilatometry. Grade 5 titanium alloys were created by blending hydridedehydride (HDH) commercially pure powder with master alloy (MA) 60/40 wt%. The dimensional effect of varying master alloy produced a maximum difference of 0.341% between an alloy with lower MA content compared to higher content during sintering. The sintering behavior of powder HDH+MA reached a nal shrinkage of 4.59%. Other powders TiH2, TiH2+MA, and Armstrong pre-alloyed had fi nal shrinkages of 9.85, 9.64, and 8.31%. The larger shrinkage powders were pressed into a peripheral component to be bonded to a HDH+MA core. Samples were sintered under a vacuum of 2x10􀀀6 torr by heating from room temperature to 1370 oC at 15 oCmin􀀀1 and holding at 1370 oC for 90 minutes. Sinter Bonded sample interfaces were examined showing the best bond to be the Armstrong j HDH+MA combination. This bond was tested using a push out test achieving shear stresses of 423 60 MPa using a pre-sintering tolerance between components of 0.065 mm and 444 37 MPa using a pre-sintering tolerance of 0.03 mm. Wrought material tested in the same manner as the sinter bonded components had a strength of 517 8 MPa. Sinter bonded samples achieved on average 82% the strength of wrought tested in the same manner. Strong bond strengths lead to a fatigue analysis of sinter bonded samples. Under various applied cyclic compressive stresses the number of cycles to failure were measured using an applied stress ratio R = 0.1. Determination of fatigue properties was done by simulating and probing in Abaqus the max tension stresses located at the bottom center of the sample. Simulations produced steady state tension stresses measured at maximum, mean, and minimum applied compressive stresses. These stresses were used to plot a S-N curve. True stress amplitudes were calculated from probed maximum and minimum stresses and the fatigue data were fi t to the Basquin empirical relation 2 = 810:4(2Nf )􀀀0:055 for sinter bonded samples and 2 = 1290:9(2Nf )􀀀0:065 for wrought samples. As a proof of concept several pressed titanium parts were combined in the green state and successfully sintered into a single component.
Ph.D. in Materials Science and Engineering, May 2018
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Title: PERFORMANCE APPRAISAL RATING GOALS: A MULTILEVEL POLICY-CAPTURING STUDY EXAMINING RATEE, RATER, AND SITUATIONAL INFLUENCES ON GOAL APPLICATION
Creator: Overfors, Christine M.
Date: 2018, 2018-05
Description: Performance ratings are a critical behavior of study in industrial and organizational psychology. For decades, researchers have sought to...
Show morePerformance ratings are a critical behavior of study in industrial and organizational psychology. For decades, researchers have sought to better understand the process managers follow to assign performance ratings. Rating goals have been proposed as the primary mechanism that managers use to determine which performance rating they will assign (e.g. Murphy & Cleveland, 1995; Murphy, 2008). This study investigated the rating goals pursued by sales managers evaluating vignettes of insurance agents using a policy-capturing approach. Rater characteristics, ratee characteristics, and a situational variable were examined to determine the influence of these factors on rating goals. Hypotheses and research questions were analyzed using hierarchical linear modeling, a statistical methodology which accounts for the inherent nesting within rating goals data. Results suggest that significant variability exists within raters and across raters in their endorsement of rating goals and that raters differ in the way they consider performance information in rating goal endorsement. In addition, some characteristics of the rater may influence the rating goals a rater chooses to endorse. Results and implications for future research are discussed.
Ph.D. in Psychology, May 2018
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Title: EARLY DETECTION OF MAINTAINABILITY ISSUES IN MEP SYSTEMS USING BIM
Creator: Barbarosoglu, Bahadir Veli
Date: 2018, 2018-05
Description: The terms maintainability and maintenance are interrelated and often perceived to be difficult to distinguish from each other. Maintainability...
Show moreThe terms maintainability and maintenance are interrelated and often perceived to be difficult to distinguish from each other. Maintainability refers to the measures and actions taken during the design phase in order to assure that the building components and the system to which it belongs can be easily maintained at minimum downtime and cost. On the other hand, maintenance refers to the measures and action taken during the operation phase in order to keep the components at the desired operational condition. The variance between designers’ and facility managers’ priorities concerning maintainability creates a gap between the design and operation phases. Maintainability is not often considered in design nor is it a priority for designers. Designers consider equipment access to be one of the least important factors related to maintenance. However, design-related maintainability issues such as equipment access problems make maintenance activities impractical if not impossible in facility operation, and increase the life cycle costs of facilities. These issues can be detected in the design phase if an appropriate tool is available, and can prevent maintenance-related problems in the operation phase. This research aims to bridge the gap between design and facility management by developing and deploying a BIM tool that brings a facility management perspective into design, and allows designers to inject maintainability considerations into the design phase. In this study, the building and construction codes and standards adopted and published by the local governments of the United States were investigated in order to identify maintainability standards related to geometric design and parametric information of building components. Parametric rule sets related to maintainability were established according to the codes and standards. From the “equipment access” perspective, a maintainability checking algorithm that can be easily customized for any building component and its rule sets was developed. In order to demonstrate the operation of the algorithm in 3D design view, the algorithm was customized for a particular piece of equipment, codded in C# programing language, and implemented as an add-in called “Maintainability Checker” to the most commonly used BIM software: Revit. A video clip of the demonstration was embedded into a questionnaire, and the questionnaire was administrated to designers and facility managers in order to validate the potential benefits of “Maintainability Checker”. A comparative analysis of designers’ and facility managers’ opinions towards maintainability and “Maintainability Checker” was conducted using SPSS. The survey results indicate that the gap between the design and post-construction phases does exist. However, the survey results also indicate that “Maintainability Checker” can bridge the gap by allowing designers to produce a better design that improves equipment maintenance access and workplace safety, facilitates the cleaning and repair of building components, reduces the number of reworks, improves the efficiency of the commissioning process, and reduces the time spent on maintenance activities, all without increasing the workload of designers. The construction industry should consider an automated maintainability check to be an essential part of the design process, create/adopt design for maintainability standards for every building component that can possibly be in a structure, and use them within BIM tools.
Ph.D. in Civil Engineering, May 2018
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Title: FROM EVERYTHING CALLED CHICAGO SCHOOL TO THE THEORY OF VARIETIES
Creator: Baciu, Dan C.
Date: 2018, 2018-05
Description: A.D.F. Hamlin’s Chicago School was rooted in the untrammeled freedom of art in America and offered bold, utilitarian solutions for early...
Show moreA.D.F. Hamlin’s Chicago School was rooted in the untrammeled freedom of art in America and offered bold, utilitarian solutions for early skyscrapers with vertical lines rising uninterrupted from the basement to the roof. Thomas Tallmadge responded to Hamlin, but redefined the term, inspired by the great American planes and their horizontal lines. Sigfried Giedion returned to the initial definition and was followed as well as opposed by many later writers. Meanwhile, William James witnessed the birth of a Chicago School of Thought around John Dewey’s pragmatist philosophy. Robert Park became the central figure in a Chicago School of Sociology that explored human nature. And in economics, Milton Friedman crusaded for free markets and free choice. Furthermore, there were Chicago Schools of Fiction, Broadcasting, Advertising, and many more. This present dissertation collected, cataloged, and evaluated everything called Chicago School. Based on this data, it is possible to tell from a collective point of view what successful Chicago Schools were. In addition, Sigfried Giedion’s school marks a turning point in history. After Giedion’s essay was published, multiple schools of thought rose to fame together. Why did this trend only come into action a century after the first mentions of a Chicago School? To understand this delay, I developed a theory based on the variability of definitions and the responsiveness of audiences. Mathematically, the Theory of Varieties builds on equations previously employed in other disciplines. In the Humanities, it may help evaluate the evolution of cultural trends.
Ph.D. in Architecture, May 2018
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Title: MULTIUSER COMMUNICATIONS FOR NETWORK CODING AND NOMA
Creator: Attang, Edidiong
Date: 2018, 2018-05
Description: A paradigm shift from single user to multiuser communications helps improve system capacity for an increasing amount of applications. Such...
Show moreA paradigm shift from single user to multiuser communications helps improve system capacity for an increasing amount of applications. Such systems such as cellular mobile radio and wireless local area networks are prone to multi-access interference. Although decoding techniques has been developed, the performance of such multi-access systems is severely degraded by increasing the number of users. Network coding increases the performance of such multi-access systems by increasing its diversity over independent or orthogonal channels at least equal to the number of users. A more resource efficient strategy ensures that the number of independent channels are less than the number of users This design also known as Non-Orthogonal Multiple Access (NOMA) provides resource efficiency with the potential of managing interference. In this thesis, a specific class of Balanced Incomplete Block designs called Steiner designs is analyzed. For this class, the decoding techniques are enhanced by exploiting the structure of these designs. However, decoding criteria for a large number of independent users is prohibitively expensive. Therefore, we provide an optimized way to search through all possible combinations of independent user data. Our work presents decoding users both from a performance oriented and objective oriented viewpoint. Work in physical layer techniques for non-orthogonal transmission is evolving. The need for finding a structured decoding scheme for large number of designs will pave the way for high data rate transmissions. Also, physical implementation and analysis of decoding techniques for a large number of users will bridge the gap between theory and practice.
Ph.D. in Electrical Engineering, May 2018
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Title: ASSESSING THE BIOLOGICAL REACTION TO IMPLANTATION OF PERIPHERAL NERVE ELECTRODE INTERFACE DEVICES
Creator: Bredeson, Samuel
Date: 2018, 2018-05
Description: It has long been suspected that tethering forces between a peripheral nerve interface device and a connector mounted on the skin can cause...
Show moreIt has long been suspected that tethering forces between a peripheral nerve interface device and a connector mounted on the skin can cause wire breakage and device failure in a relatively short time. This has been confirmed by our own experimental observations. Devices and methods have been developed that eliminate the need for a wire tether by replacing it with a wireless power and data transmission system based on mutual induction. Wireless systems, however, require the use of electronic components placed directly on the nerve being interfaced, which could be an alternate source of trauma to the tissue. An additional difficulty with wireless devices is their placement within the body. Wireless power and data transfer often depend on the successful coupling of inductive coils in the transmitter and receiver. The strength of this coupling changes with the distance, alignment, and size difference between the two coils. This creates practical limits on where implanted devices can be placed within the body. Typically, implantable wireless devices utilizing mutual induction approach this problem by making their inductive coils larger. The relationship between on-nerve device size and damage to the interfaced tissue has not been thoroughly studied for implantable peripheral nerve interface devices. Two experimental phases were devised to investigate the biological impact in-vivo of wired versus wireless devices and increasing the size of wireless devices. First, a 14-month study was performed to assess the chronic usability of this type of interface. Next, a 10-week study was performed to closely investigate the tissue response to implanted devices. The conclusion of this work is that for wireless modules integrated with peripheral nerve cu s, there is not a correlation between electronics package size and overall nerve health as based upon histological and functional assays. This suggests that use of untethered wireless, rather than tethered wired, interfaces may be better for the health of the nerve interface even when utilizing a broad range of wireless electronic package sizes.
Ph.D. in Biomedical Engineering, May 2018
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Title: OPTIMIZATION IN MULTI-RADIO MULTI-CHANNEL WIRELESS NETWORKS WITH DIRECTIONAL ANTENNAS
Creator: Zhou, Lei
Date: 2018, 2018-05
Description: In this thesis throughput optimal and delay minimization problems are discussed in multi-radio multi-channel (MRMC) wireless networks with...
Show moreIn this thesis throughput optimal and delay minimization problems are discussed in multi-radio multi-channel (MRMC) wireless networks with directional antennas (DR). As for throughput optimal problem, we adopt a multi dimensional conflict graph (MDCG) in MRMC-DR network under protocol interference model, using the concept of Link-Radio- Antenna-Channel tuple links, to facilitate mapping the original MRMC-DA network into a simple virtual single-radio single-channel (SRSC) network, on which the capacity optimization problem can be formulated as a linear program. To circumvent searching the exponentially many independent sets, we apply the delayed column generation (DCG) method to design our algorithm. On the other hand, with regard to delay minimization problem, we present a minimum length schedule (MLS) to minimize end-to-end delay while satisfying required demand. A tuple-based model is applied to help address this problem, and a more realistic model—physical interference model is adopted here to better present interference relationships between wireless links. DCG is also used here to avoid going through all independent sets, and different strategies have been raised to address situations with fixed transmission rate or variable transmission rate. Moreover, both routing and scheduling can be jointly achieved by searching for optimal solutions of our problem formulation.
Ph.D. in Computer Engineering, May 2018
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Title: SYNTHESIS AND REACTIVITY OF ORGANOMETALLIC VAPOR PRECURSORS IN DEPOSITING THIN FILM MATERIALS
Creator: Zhang, He
Date: 2018, 2018-05
Description: Developing novel vapor precursors for vapor depositions such as atomic layer deposition (ALD) is critical for enabling new thin film materials...
Show moreDeveloping novel vapor precursors for vapor depositions such as atomic layer deposition (ALD) is critical for enabling new thin film materials and advanced processes. 2D materials such as transition metal dichalcogenides (TMDs) are promising materials for TFETs and diffusion barriers due to their narrow, direct band gap, and atomic thickness. In the potential electronic applications of TMDs materials, low-temperature, non-corrosive process is desired and even required to avoid thermal budget to the devices and sensitive components. Besides novel organometallic precursors, understanding the surface reaction mechanism is also necessary to achieve well-controlled material growth and obtain crystalline materials at lower temperature. In this dissertation, two novel synthetic methods to obtain crystalline TMDs materials such as tungsten disulfide (WS2) were developed, utilized metal hydride compound to synthesize at room temperature and heteroleptic compound to illustrate reaction mechanism. Reaction mechanism on the surface to produce metals chalcogenides including oxidation state changes and ligand behaviors during the nucleation using organometallic precursor on surfaces were investigated and observed with synchrotron X-ray absorption spectroscopy (XAS). Conventional tellurium sources have very limited reactivity towards tungsten. To overcome the low reactivities between W and Te sources, redox potential of organometallic Te and W precursors was utilized and achieved low-temperature synthesis of tungsten ditelluride (WTe2). Novel heteroleptic precursors design was also extended to Zr and Hf precursors. Heteroleptic Zr and Hf precursors were synthesized with high volatility and thermals stability. The heteroleptic precursors also showed high reactivity toward proton sources and selectivity between ligands. Metal chalcogenides deposition would be preferred with oxygen-free precursors. Organometallic precursors are typically more reactive than simple metal carbonyls or metal halides, and those organometallic precursors with a clear proton-transfer mechanism can allow ligands to be removed easily and obtain materials with high purity. Currently, tungsten precursors to synthesis TMDs material are commonly limited in metal carbonyls and metal chlorides, and the sulfurizations were performed at high temperature. By using more reactive organometallic precursors, the reaction between tungsten and chalcogenide sources can be initiated at lower temperature, highly reactive metal hydride and redox potential of metal complex were also utilized to boost reactivity. Well-designed ligands structures were employed to chemically enhance the crystallinity through the selectivity between ligands. Heteroleptic precursors are typically expected to have a better self-limiting control in synthesis, due to the different type of ligands could selectively react in each step. These enhanced precursor chemistries and understanding mechanism lead to better control of the synthesis of materials.
Ph.D. in Chemistry, May 2018
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Title: ENSURING NAVIGATION INTEGRITY AND CONTINUITY USING MULTI-CONSTELLATION GNSS
Creator: Zhai, Yawei
Date: 2018, 2018-05
Description: Global navigation satellite system (GNSS) measurements are vulnerable to faults including satellite and constellation failures, which can...
Show moreGlobal navigation satellite system (GNSS) measurements are vulnerable to faults including satellite and constellation failures, which can potentially lead to catastrophic consequences in safety-critical applications. To mitigate their impact, receiver autonomous integrity monitoring (RAIM) fault detection has been designed and used in aviation as a backup navigation tool. Future GNSS has been foreseen to provide dramatically increased measurement redundancy and reduced measurement error. These revolutionary developments, together with important advancements in the RAIM concept itself, will open the possibility to independently support aircraft navigation using GNSS, from takeoff, through en-route flight and final approach to landing, with minimal investment in ground infrastructure. Therefore, this research focuses on developing new dual-frequency, multi-constellation advanced RAIM (ARAIM) fault detection and exclusion methods to ensure high navigation integrity and continuity. In this thesis, the theoretical basis is established to quantify the contributions of fault events and unscheduled satellite outages on continuity risk. Accordingly, the need for airborne fault exclusion is assessed, and the requirements for the exclusion function itself are speci fied. To improve continuity, a new fault exclusion scheme is developed, for which the real-time implementation of the algorithm is described and the associated integrity risk bound is derived. With the theoretical methods being fully characterized, this thesis comprehensively quanti es the achievable ARAIM navigation performance over various numbers and qualities of constellations. The results show high service availability can be achieved using multi-constellation GNSS, while meeting both integrity and continuity requirements. Furthermore, this work investigates the impact of test statistic time correlation on integrity and continuity risk, and rigorously derives the new methods to evaluate the actual risk over the exposure time. The results show that the false alarm probability is two orders of magnitude higher than previously thought. A feasible solution to resolve this issue at the user receiver is provided, and the performance is analyzed. The most signifi cant new feature of ARAIM is the integrity support message (ISM), which provides assertions on the GNSS signal-in-space performance. This dissertation describes the design, analysis, and evaluation of the offline ground monitor, which aims at validating the ISM broadcast to the users. The proposed architecture utilizes a worldwide network of sparsely distributed reference stations, and paramet- ric satellite orbital models to estimate the satellite position and clock. Two separate analyses, covariance analysis and model delity evaluation, are carried out to respec- tively quantify the impact of measurement errors and of residual model errors on the estimation. The results indicate this ground monitor design is adequate for ARAIM ISM validation.
Ph.D. in Mechanical and Aerospace Engineering
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Title: ELECTROACTIVE COLLOIDAL MATERIALS DERIVED FROM POLYOXOMETALTES
Creator: Swenson, Lasalle
Date: 2018, 2018-05
Description: Polyoxometalates (POMs) are transition metal-oxide clusters formed by the early transition metals V, Mo, and W. As a subclass of metal oxides,...
Show morePolyoxometalates (POMs) are transition metal-oxide clusters formed by the early transition metals V, Mo, and W. As a subclass of metal oxides, POMs have a number of prototypical physical and chemical properties: solubility; thermal and solvent stability; Brønsted acidity; chemical and photochemical redox activity; photo- and electrochromism; and magnetic properties. POMs have been applied to a variety of technical areas, including catalysis, photocatalysis, biomedicine, and magnetism. As discreet molecular units having well-defined chemical properties, POMs are attractive building blocks for new materials whose properties could be rationalized in terms of their constituents at the molecular level. Towards that end, we have synthesized and characterized a series of new extended structure materials containing the organofunctionalized polyoxocationic species, [NaVIV 6O6{(OCH2CH2)2N(CH2CH2OH)}6]+ (NaV6 +). Three of the new materials are classified as POM ionic crystals and contain NaV6 + and Keggin polyoxoanions [(PW12O40)3-, (SiW12O40)4- or (SiMo12O40)4-] as molecular constituents: [NaVIV 6O6{(OCH2CH2)2N(CH2CH2OH)}6]3(PW12O40)·12H2O G1, [NaVIV 6O6{(OCH2CH2)2N(CH2CH2OH)}6]4(SiW12O40)·20H2O G2, and [NaVIV 6O6{(OCH2CH2)2N(CH2CH2OH)}6]3(HSiMo12O40)·13H2O G3. The final two materials (hereafter C1 and C2) are obtained as redistributable colloids derived from NaV6 + and the mixed-addenda Keggin structure polyoxoanion (PVW11O40)4- (VW11 4-). C1 contains the single polyoxocation constituent NaV6 +, while C2 contains both NaV6 + and VW11 4-. We have characterized the materials using PXRD, FTIR and UV-vis spectroscopy, TGA, SEM/EDX, elemental analysis, and cyclic voltammetry. G1, G2, and G3 are nanocrystalline and composite in nature, containing intact oxometallic cores of their respective polyoxoanion and polyoxocation building block units. Intercluster Coulombic interactions are the driving force of composite formation. These are the first materials derived from Coulombic interactions of polyoxoanions with covalently organo-functionalized polyoxocations. Cl and C2 are colloidal in nature and obtained in the form of micrometer-scale monoliths. They are the first POM-derived colloidal materials that are readily synthesized, isolated, and redistributed in practical quantities. The monoliths are insoluble in a variety of organic media including lower aliphatic alcohols. They readily form thin-films (δ < 100 um) by solvent casting. Owing to their extended nature, redistributable and isolable properties, the materials C1 and C2 may considered a new form of POM heterogenation. We use cyclic voltammetry (CV) to show that the constituents of the new materials are electrochemically addressable; a finding which opens the door to possible applications in sensing, energy storage and (electro-)chemical catalysis. With an eye towards technological applications, we demonstrate the systematic deposition of C2 onto indium tin oxide (ITO) using electrophoretic deposition, and show (CV) that we can access the electrochemical redox centers of its constituents following deposition. These materials demonstrate the activity of NaV6 + as a soft-chemical constituent partner to similar scale POM counter-anions, suggesting further synthetic investigations using this unique species. Owing to the redox properties of their constituents, the new materials present hybrid surfaces that may be considered intriguing prospective (multifunctional) heterogeneous oxidation catalysts. The electroactive nature of the materials also suggests prospective applications in energy storage and conversion, for example, as the active components of ion-insertion type capacitors and batteries. Electrocatalysis and sensing are also prospective application areas. The extended, as opposed to molecular, structure of the materials, suggests possible advantages when forming polymeric composites with conducting and nonconducting polymers, such as: an increased resistance to leeching, the emergence of favourable polymeric film mechanical properties, and the emergence of favorable electron and counterion tranport properties.
Ph.D. in Chemistry, May 2018
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Title: SWITCHING OSCILLATION OF HIGH-FREQUENCY WIDE BANDGAP POWER SEMICONDUCTOR DEVICES
Creator: Liu, Tianjiao
Date: 2018, 2018-05
Description: Wide bandgap (WBG) power semiconductor devices can operate at high voltage, high switching frequency and high temperature. However, the...
Show moreWide bandgap (WBG) power semiconductor devices can operate at high voltage, high switching frequency and high temperature. However, the extremely fast switching characteristics, when combining parasitic components from the device package and power electronics circuit, are unfortunately accompanied by undesirable switching oscillations. In this thesis, switching oscillations observed in the WBG devices are studied. Firstly, a survey on oscillations in the general high-frequency power electronics circuit is carried out including the impacts of oscillation, causes of oscillation and mitigation of oscillation. Moreover, theoretical studies of the WBG switching performance and switching oscillations are performed based on spectrum analysis. The mathematical derivation reveals that the oscillation tends to enhance certain regions in the electromagnetic interference (EMI) spectrum by inducing a noise peak. In addition, modeling and analysis of silicon carbide (SiC) MOSFET switching oscillations are presented by developing equivalent circuit models for the turn-on and turn-off switching, respectively. Damping techniques design guidelines are provided based on the modeling analysis. Last but not least, a new technique to accurately characterize the parasitic inductances of power devices in discrete and module packages based on two-port scattering (S) parameters measurement is proposed. The approach is first verified with high frequency circuit simulation and then experimentally validated through case studies of a number of discrete devices and power modules.
Ph.D. in Electrical Engineering, May 2018
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Title: DEVELOPMENT OF A HYDROGEL NANOPARTICLE SYSTEM FOR SUSTAINED DELIVERY OF ANIGOGENIC FACTORS FOR THERAPEUTIC NEOVASCULARIZATION
Creator: Young, Daniel A
Date: 2018, 2018-05
Description: Neovascularization requires controlled and sustained delivery of proangiogenic factors to stimulate reperfusion of ischemic tissues. Tissue...
Show moreNeovascularization requires controlled and sustained delivery of proangiogenic factors to stimulate reperfusion of ischemic tissues. Tissue engineering strategies for therapeutic neovascularization have used proangiogenic, recombinant growth factors to direct vessel development. Recently, peptides that mimic the bioactivity of growth factors have emerged as therapeutics for a variety of drug delivery applications, including therapeutic neovascularization. We designed hydrogel nanoparticles to provide sustained and tunable di usion-based release of a proangiogenic peptide, QK, and a vessel stabilizing peptide, Vasculotide (VT). These nanoparticles were combined with a tissue engineering sca old to promote tissue neovascularization. We used this nanocomposite system, utilizing peptide loaded hydrogel nanoparticles embedded in an implantable sca old, to investigate the e cacy of a dual peptide delivery strategy for therapeutic neovascularization. Inverse phase mini-emulsion polymerization (IPMP) was used to generate crosslinked poly(ethylene) glycol (PEG) hydrogel nanoparticles. We characterized the nanoparticles in terms of their swelling ratio, mesh size, surface charge ( -potential), and particle size distributions. We developed several nanoparticle formulations using various sizes and molar concentrations of PEG chains to study the e ects of crosslink density on peptide release kinetics. This resulted in the formation of nanoparticles with low and high crosslink density as well as time-dependent variations in network density due to hydrolysis. We utilized two di erent loading techniques, peptide entrapment during IPMP and peptide post-loading into the nanoparticles, and found both to be e ective via peptide loading measurements and release kinetic studies. In the case of entrapment loading, peptides were included in the aqueous precursor during nanoparticle IPMP. Peptide release kinetics were tuned through adjustments in nanoparticle crosslink density. The resulting nanoparticle crosslink density impacted both peptide loading and fractional release, as studies showed higher crosslink density nanoparticles resulted in slower peptide release. The IPMP process preserved QK secondary structure and bioactivity, as con rmed with released peptide using circular dichroism spectroscopy and a Matrigel tubulogenesis assay, respectively. In the case of the post-loading method, pristine nanoparticles were soaked in various concentrations of either QK or VT. Unlike with the entrapment loading method, crosslink density of the nanoparticles had little e ect on release kinetics. However, much higher mass amounts of peptide could be loaded using this method and thus this method was chosen for the in vivo studies. Next, we developed a hydrogel nanocomposite sca old system to sequester nanoparticles for implantation. We characterized the nanocomposite sca old system experimentally and theoretically using one-dimensional transport models of molecular di usion. We estimated peptide di usion coe cients from nanoparticles and the nanocomposites under perfect sink conditions. Importantly, we found this system capable of providing previously reported therapeutic thresholds of QK and VT. Finally, the in uence of sustained release of QK and VT on neovascularization was evaluated using a subcutaneous rat implant model. Results demonstrated statistically higher increases in perfused vessel density from peptide loaded nanocomposite sca olds as compared to sca olds where peptide was simply entrapped. These results suggest that controlled release of proangiogenic peptides from the developed nanoparticle system holds great potential for ischemic tissue repair.
Ph.D. in Biomedical Engineering, May 2018
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Title: Make a Connection: Library Services for International Students: Make_a_connection_internationalstudents
Creator: Han, Yi, Ruswick, Jannelle
Date: 2011-10, 2011-10-20
Description: This presentation for the Illinois Library Association Annual Conference at the Rosemont Convention Center focuses on ways to adapt library...
Show moreThis presentation for the Illinois Library Association Annual Conference at the Rosemont Convention Center focuses on ways to adapt library services, orientations, and online and in-person instruction to meet international students' informational needs.
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Title: DESIGN OF WOUND FIELD SYNCHRONOUS MACHINES AND HYBRID EXCITATION SYNCHRONOUS MACHINES FOR ELECTRIC VEHICLE TRACTION WITH BRUSHLESS CAPACITIVE FIELD EXCITATION
Creator: Di Gioia, Antonio
Date: 2018, 2018-05
Description: The focus of this dissertation is to describe the electromagnetic modeling and optimization, mechanical modeling, thermal simulation and...
Show moreThe focus of this dissertation is to describe the electromagnetic modeling and optimization, mechanical modeling, thermal simulation and experimental characterization of two prototype permanent magnet-free high power density wound eld synchronous machines (WFSMs) and one prototype of permanent magnet-wound eld hybrid excitation synchronous machine (HESM) for electric and hybrid-electric vehicle traction applications. The WFSMs and HESM are designed for brushless rotor eld excitation using an axial ux hydrodynamic capacitive power coupler (CPC) but can also be operated with a brush and slip rings excitation system. A exible design environment has been developed for large scale multi-objective optimization of the machines, particularly focusing on the use of a static electro-magnetic solver, FEMM, and the extension of the software routines to reconstruct the transient behavior of rotating electrical machines. The prototypes are designed to operate with a spray cooling system with automatic transmission uid (ATF Dexron VI) in order to reach power densities comparable to the commercial permanent magnet synchronous machines (PMSMs) for similar applications. The spray cooling system was simulated with a commercial software (MotorCAD) and the modeling approach validated with experimental characterization. The spray cooling system was modi ed to include thermal circuit paths that emerged during the testing of the prototypes and integrated in the current release of the software. The experimental characterization shows promising results, with peak output power at a base speed of 4,000 RPM exceeding 80 kW for the WFSM prototypes, and a continuous power output of 60 kW with the spray cooling system. The prototyped WFSMs achieve volumetric and speci c torque and power densities of 17.22 Nm/l, 4.69 Nm/kg, 7.19 kW/l, and 1.95 kW/kg. The experimental data collected for the HESM prototype shows a no-load rotor-side ux weakening capability that enables constant power speed ratio of 10:1 during operation and provides a exible platform for machine characterization and advanced control development for one monoaxial and one biaxial hybrid excitation synchronous machine con gurations. The design of the HESM prototype was obtained with an integration of analytical sizing equations for the initial exploration of the design space and FEA methods for detailed modeling of the nal prototype features.
Ph.D. in Electrical Engineering, May 2018
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Title: HIGH TEMPERATURE GRAIN BOUNDARY ENGINEERING OF POWDER PROCESSED NICKEL BASED SUPERALLOYS
Creator: Mccarley, Joshua B.
Date: 2018, 2018-05
Description: The concept of grain boundary engineering (GBE) has been effectively utilized to improve the properties of polycrystalline Nickel based...
Show moreThe concept of grain boundary engineering (GBE) has been effectively utilized to improve the properties of polycrystalline Nickel based superalloys via triggering the formation of special High-angle grain boundaries which are highly coherent. Current processing routes which implement GBE often require multiple iterations of room temperature deformation also characterized as cold work, followed by short annealing cycles whereby each applied iteration results in limited to modest enhancements in the fraction of the aforementioned special grain boundaries. As such, a substantial number of iterations are required to obtain fractions large enough (>50%) to effectively yield improved resistance to corrosion, creep, and fatigue. The current application of GBE on high-strength materials is not suitable for the production of large, complex-shaped structures, and has also been noted to increase manufacturing lead time and cost. In this investigation, alternative processing routes which utilize GBE at elevated temperatures for powder processed Nickel based superalloys used as turbine discs in gas turbine engines manufactured by Rolls-Royce. The material which serves as the central focus of the forthcoming investigation is an experimental low stacking fault energy Nickel based superalloy containing a cobalt concentration of 24 wt.%. A preliminary study which focused on the effects of hot deformation parameters similar to typical industrial applications revealed the materials ability to enhance its Σ3 twin boundary length fraction from 21% to 53% following a single deformation/anneal cycle. Subsequently, the investigated deformation parameters displayed a near consistent triggering of dislocation based plasticity mechanisms which promoted the formation of annealing twin boundaries. Although the experimental Nickel based superalloy exhibited the ability to promote extensive fractions of annealing twins, the resultant grain boundary characters produced via hot deformation displayed varying magnitudes of dynamically recrystallized grains which are generally considered to be detrimental in GBE practices. Mechanisms which assist in optimizing the formation of Σ3 twin boundaries during high-temperature GBE were further investigated. The enhanced cobalt concentration possessed by the experimental alloy was observed to have effectively enhanced the materials ability to rapidly store high magnitudes of strain energy upon hot deformation when compared to a commercially available Nickel based superalloy possessed a lower Co. concentration. Reducing the volume fraction of primary gamma prime precipitates present in the experimental alloys microstructure was noted to have effectively slowed the onset of dynamic recrystallization, while still promoting favorable fractions of annealing twins. A critical strain was later identified at which the onset of dynamic recrystallization was predominately avoided in the experimental alloy during hot deformation, and the strain induced boundary migration mechanism was effectively triggered which promoted the largest observed length fractions of Σ3 twin boundaries. A final investigation which considered what effect distinct microstructural features have on the kinetics which drive twin formation was also performed to assist in providing insight on optimizing applications related to GBE for advanced turbine engines.
Ph.D. in Materials Science and Engineering, May 2018
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Title: BAXΔ2: FROM FUNCTIONAL DOMAINS TO CANCER CORRELATION
Creator: MaÑas NÚÑez, Adriana
Date: 2018, 2018-05
Description: BaxΔ2 is a functional pro-apoptotic Bax isoform, originally identified in cancer patients with microsatellite instability. Here we performed...
Show moreBaxΔ2 is a functional pro-apoptotic Bax isoform, originally identified in cancer patients with microsatellite instability. Here we performed an extensive study on BaxΔ2, covering the structure-function relationship, the clinical potential, and the human tissue expression profile. Unlike Baxa, BaxΔ2 forms aggregates and triggers non-mitochondrial cell death through caspase 8. However, the functional domain(s) responsible for BaxΔ2 unique behavior were elusive. Here we show that disruption of helix α1 makes Baxα mimic BaxΔ2, but other alterations in the N-terminus have no significant impact. We found that the core region is key for aggregation, but is not sufficient to trigger cell death. The Cterminal helical conformation, not its primary sequence, appears to be critical for caspase 8 activation. As BaxΔ2 shares core and C-terminal with most Bax isoforms, our results indicate an intrinsic potential for aggregate-mediated caspase 8-dependent cell death in other Bax family members. BaxΔ2 has been shown to sensitize cancer cells to chemotherapy, but it is a very unstable protein. Therefore, we screened a panel of proteasome inhibitors in colorectal cancer cells with different Bax statuses. We found that proteasome inhibitors can block BaxΔ2 degradation without affecting the levels of Baxa or Bcl-2. Among the inhibitors tested, bortezomib and carfilzomib were able to induce significantly higher cell death in BaxΔ2-positive cells than in cells with Baxa or no Bax. Furthermore, bortezomib-induced cell death in BaxΔ2-positive cells was predominantly dependent on the caspase 8/3 pathway. These results suggest that BaxΔ2 can selectively sensitize cancer cells to proteasome inhibitors. As many cancers have microsatellite mutations, we screened BaxΔ2 protein expression in 1090 samples of tumor and healthy tissues from several organs. We found that BaxΔ2 is expressed in 1% to 5% of cells in most organs, predominantly in healthy tissues. Production of BaxΔ2 requires a guanine deletion in the microsatellite region, but the great majority of BaxΔ2-positive tissues contained no mutation at genomic or transcript levels. Therefore, we tested Programed Ribosomal Frameshift (PRF) as a possible BaxΔ2 expression mechanism, using a double tagged construct with no mutation. We found that, though rare, PRF can lead to expression of BaxΔ2. In conclusion, BaxΔ2 can be expressed without a genetic mutation. In conclusion, BaxΔ2 is a unique isoform whose expression is the product of the extreme plasticity of the Bax gene and the biochemical circumstances in the cell. As an example of non-traditional expression, it opens the door to a whole new proteome expressed by alternative mechanisms both under physiological and pathological conditions.
Ph.D. in Biology, May 2018
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