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Title: Role of a alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor on methylmercury-induced calcium dysregulation on motor neurons
Creator: Colón-Rodríguez, Alexandra
Date: 2017
Collection: Electronic Theses & Dissertations
Description: Methylmercury (MeHg) is a persistent environmental neurotoxicant to which humans are exposed mainly through the consumption of fish. MeHg leads to neuronal cell death in acute or chronic exposure and its mechanism of toxicity is not yet understood. Due to its high prevalence in the environment and its mechanism of toxicity MeHg has been considered a possible contributor to the development of Amyotrophic Lateral Sclerosis (ALS). Alterations in glutamate reuptake and Ca2+ regulation in ALS and...
Show moreMethylmercury (MeHg) is a persistent environmental neurotoxicant to which humans are exposed mainly through the consumption of fish. MeHg leads to neuronal cell death in acute or chronic exposure and its mechanism of toxicity is not yet understood. Due to its high prevalence in the environment and its mechanism of toxicity MeHg has been considered a possible contributor to the development of Amyotrophic Lateral Sclerosis (ALS). Alterations in glutamate reuptake and Ca2+ regulation in ALS and after MeHg exposures have been well documented. Most importantly, MeHg-induced alterations in intracellular Ca2+ ([Ca2+]i) in motor neurons lead to early onset ALS-like phenotype in the superoxide dismutase 1 (SOD1-G93A) mouse, a mouse model genetically susceptible to ALS. One of the ion channels that contribute to the alterations in [Ca2+]i observed in ALS and after MeHg exposure is the ionotropic glutamate receptor α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA). My research has focused on characterizing the effects of MeHg on motor neurons in vitro. I used two cell lines: a mouse motor neuron hybrid cell line NSC34 and an induced pluripotent stem cell derived-motor neuron (hiPSC-MN) cell line of human origin. I investigated MeHg toxicity in these cell types and on AMPA receptors in order to understand the role these ion channels play in the observed alterations in [Ca2+]i. Results from the studies in this dissertation demonstrate that MeHg exposure in vivo or in vitro lead to alterations in the AMPA receptor and the RNA editing enzyme ADAR2 gene expression. Also, that hiPSC-MNs are more susceptible than NSC34 cells to MeHg toxicity observed as an earlier concentration dependent cell death. I also identified that MeHg induces a bi-phasic increase in [Ca2+]i in hiPSC-MNs and Ca2+ permeable AMPA receptors are mediating those increases. Taken together these results suggest a potential role of the AMPA receptors in MeHg-induced toxicity in MNs. These findings contribute to the understanding of MeHg-induced toxicity in motor neurons and provide a platform for ongoing studies in our lab which are focused on identifying the underlying mechanisms by which MeHg is contributing to the accelerated onset of ALS-like phenotype.
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Title: Experimental and numerical investigation of confined premixed flame
Creator: Najim, Younis Mahal
Date: 2017
Collection: Electronic Theses & Dissertations
Description: Understanding the dynamics of premixed flames propagating during constant volume combustion is key to enhancing the performance of existing combustion devices, which provide 80% of the world’s energy supply, and reducing the impact of pollution on the environment. This work experimentally and numerically investigates confined premixed flame propagation in an initially quiescent mixture. Three combustion chambers are used; a curved wave disc engine channel and rectilinear channels of aspect...
Show moreUnderstanding the dynamics of premixed flames propagating during constant volume combustion is key to enhancing the performance of existing combustion devices, which provide 80% of the world’s energy supply, and reducing the impact of pollution on the environment. This work experimentally and numerically investigates confined premixed flame propagation in an initially quiescent mixture. Three combustion chambers are used; a curved wave disc engine channel and rectilinear channels of aspect ratio 7 and 10. The mixture is methane/air and syngas (H2/CO)/air initially at atmospheric pressure and room temperature. The channel walls are assumed to be isothermal to incorporate the effect of heat transfer. For two-dimensional analysis, the reaction rate is modeled using both detailed and reduced kinetic mechanisms. The mass diffusion is investigated using three different diffusion models with different levels of approximation; the multicomponent diffusion model of Chapman-Enskog including the Soret effect; the mixture-averaged model; and constant Lewis number. For three-dimensional analysis, a large eddy simulation coupled with the transport equation of the reaction progress variable is used. In this work, the reaction rate predicted using the Boger model of algebraic flame surface density is modified by incorporating a transient flame speed that accounts for the variation in the temperature and pressure of the unburned gases. The experimental measurements include schlieren photography to track the flame structure and propagation speed, and the pressure-time history during the combustion process is measured by a pressure sensor mounted in the channel wall. The experimental measurements validate the numerical simulation results and provide further understanding of the flame and pressure dynamics. Unlike behavior previously reported in straight or 90◦ bend channels, premixed flame propagation in the wave disc engine channel exhibits different features: the convex tulip flame converts back into a concave flame and thus reveals the influence of channel geometry on flame evolution. The experiments show that the rate of pressure change eventually becomes negative mainly due to heat losses that engender a correspondingly slower flame propagation during the final stage of burning. The analysis of the numerical results reveals the effect of the interaction between the flame front, pressure field, and flame-induced flow on flame evolution during all stages of flame structure development. The results also demonstrate that both multicomponent diffusion with the Soret effect and the mixture-averaged model produce slightly different results in flame speed, structure, peak temperature, and average pressure for the methane/air mixture, while the deviation is more pronounced for syngas flames. The methane/air flame produced by the unity Lewis number model, however, lags behind its counterparts during early stages and dramatically accelerates, at which time the values of peak temperature and average pressure show unrealistic behavior. Furthermore, unity Lewis number flames develop an artificial second tulip flame after the first tulip flame is annihilated. This second tulip flame is neither observed in the Chapman-Enskog and mixture-average simulations, nor in the experiments. This reveals the role of the Lewis number in the intrinsic thermodiffusive flame instabilities and tulip flame formation. The three-dimensional simulation uncovers an interesting behavior for the flame structure that is introduced here as a “transverse tulip” flame, which has not been previously reported. The “transverse tulip” flame evolves in the direction perpendicular to that of the initial tulip flame after the latter undergoes the transition from cusped convex back to the concave finger shape. The commonly used Zimont model produces an unrealistically diffused flame front. The large eddy simulation coupled with the here-modified algebraic flame surface density overcomes this issue and reproduces the experimental observations of the flame structure, pressure-time history, and burning time with good agreement.
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Title: Fluid animation on deforming surface meshes
Creator: Wang, Xiaojun (Graduate of Michigan State University)
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "We explore methods for visually plausible fluid simulation on deforming surfaces with inhomogeneous diffusion properties. While there are methods for fluid simulation on surfaces, not much research effort focused on the influence of the motion of underlying surface, in particular when it is not a rigid surface, such as knitted or woven textiles in motion. The complexity involved makes the simulation challenging to account for the non-inertial local frames typically used to describe the...
Show more"We explore methods for visually plausible fluid simulation on deforming surfaces with inhomogeneous diffusion properties. While there are methods for fluid simulation on surfaces, not much research effort focused on the influence of the motion of underlying surface, in particular when it is not a rigid surface, such as knitted or woven textiles in motion. The complexity involved makes the simulation challenging to account for the non-inertial local frames typically used to describe the motion and the anisotropic effects in diffusion, absorption, adsorption. Thus, our primary goal is to enable fast and stable method for such scenarios. First, in preparation of the material properties for the surface domain, we describe textiles with salient feature direction by bulk material property tensors in order to reduce the complexity, by employing 2D homogenization technique, which effectively turns microscale inhomogeneous properties into homogeneous properties in macroscale descriptions. We then use standard texture mapping techniques to map these tensors to triangles in the curved surface mesh, taking into account the alignment of each local tangent space with correct feature directions of the macroscale tensor. We show that this homogenization tool is intuitive, flexible and easily adjusted. Second, for efficient description of the deforming surface, we offer a new geometry representation for the surface with solely angles instead of vertex coordinates, to reduce storage for the motion of underlying surface. Since our simulation tool relies heavily on long sequences of 3D curved triangular meshes, it is worthwhile exploring such efficient representations to make our tool practical by reducing the memory access during real-time simulations as well as reducing the file sizes. Inspired by angle-based representations for tetrahedral meshes, we use spectral method to restore curved surface using both angles of the triangles and dihedral angles between adjacent triangles in the mesh. Moreover, in many surface deformation sequences, it is often sufficient to update the dihedral angles while keeping the triangle interior angles fixed. Third, we propose a framework for simulating various effects of fluid flowing on deforming surfaces. We directly applied our simulator on curved surface meshes instead of in parameter domains, whereas many existing simulation methods require a parameterization on the surface. We further demonstrate that fictitious forces induced by the surface motion can be added to the surface-based simulation at a small additional cost. These fictitious forces can be decomposed into different components. Only the rectilinear and Coriolis components are relevant to our choice of local frames. Other effects, such as diffusion, adsorption, absorption, and evaporation are also incorporated for realistic stain simulation. Finally, we explore the extraction of Lagrangian Coherent Structure (LCS), which is often referred to as the skeleton of fluid motion. The LCS structures are often described by ridges of the finite time Lyapunov exponent (FTLE) fields, which describe the extremal stretching of fluid parcels following the flow. We proposed a novel improvement to the ridge marching algorithm, which extract such ridges robustly for the typically noisy FTLE estimates even in well-defined fluid flows. Our results are potentially applicable to visualizing and controlling fluid trajectory patterns. In contrast to current methods for LCS calculation, which are only applicable to flat 2D or 3D domains and sensitive to noise, our ridge extraction is readily applicable to curved surfaces even when they are deforming. The collection of these computational tools will facilitate generation of realistic and easy to adjust surface fluid animation with various physically plausible effects on surface."--Pages ii-iii.
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Title: Effects of dimensions of word knowledge and their accessibility on different levels of reading comprehension in adolescent EFL learners
Creator: Choi, Yunjeong
Date: 2017
Collection: Electronic Theses & Dissertations
Description: Researchers have investigated that different dimensions of word knowledge (breadth versus depth) may play distinct roles in second language (L2) reading comprehension. Yet, little research has addressed how learners’ efficiency of accessing those dimensions of knowledge functions in their comprehension (i.e., the issue of knowledge availability versus accessibility in Cremer and Schoonen, 2013), not to mention comprehension at different levels. To fill gaps in previous research and enrich our...
Show moreResearchers have investigated that different dimensions of word knowledge (breadth versus depth) may play distinct roles in second language (L2) reading comprehension. Yet, little research has addressed how learners’ efficiency of accessing those dimensions of knowledge functions in their comprehension (i.e., the issue of knowledge availability versus accessibility in Cremer and Schoonen, 2013), not to mention comprehension at different levels. To fill gaps in previous research and enrich our knowledge about the lexical basis of L2 reading comprehension, the present study examined how different dimensions of L2 word knowledge and their respective accessibility function concurrently in explaining different levels of L2 reading comprehension in adolescent English as a Foreign Language (EFL) learners in Korea. To achieve this research goal, the present study defined lexical competence by distinguishing between vocabulary breadth and depth knowledge as well as between knowledge availability and accessibility. A number of tasks were employed to measure participants’ lexical competences: three paper-and-pencil tests for knowledge availability and three researcher-developed, computer-based tests for knowledge accessibility documenting response accuracy as well as latency. Reading comprehension was measured with the Gates-MacGinitie Reading Comprehension Test (MacGinitie & MacGinitie, 1992), which assessed both literal and inferential comprehension. In addition, the participants’ working memory and grammatical knowledge were also measured. The following key research findings were revealed. First, Confirmatory Factor Analysis analyses confirmed that knowledge of individual word meanings (breadth availability) and the ability to activate that knowledge efficiently (breadth accessibility), and knowledge of meaning relations among words (depth availability) and the ability to access that knowledge efficiently (depth accessibility) are distinctive constructs under the conceptualization of lexical competence. Second, availability and accessibility of depth knowledge were the only predictors that made significant contributions to reading comprehension when the impacts of those of breadth knowledge and working memory were controlled for. Within vocabulary depth, availability played a more important role than did accessibility. Availability and accessibility of breadth knowledge made no unique contribution to reading comprehension over and beyond those of depth knowledge. Third, the patterns of predictive roles of each lexical competence in reading comprehension did not seem substantially different between literal and inferential comprehension, confirming a stronger impact of depth knowledge, both availability and accessibility, than of breadth knowledge, and of availability of depth knowledge than of accessibility. However, the involvement of depth knowledge, particularly availability, seemed greater in inferential comprehension than in literal comprehension. These findings enriched our understanding about the lexical basis of L2 reading comprehension, particularly, the importance of efficient access to semantic network knowledge for textual reading and potentially differential involvement of semantic network knowledge in different levels of comprehension. Pedagogically, they suggested that vocabulary instruction should provide a learning environment where new words are provided in a meaningful reading context so that learners can establish a semantic network in their lexicon and continue developing, expanding, and consolidating the lexicon as they learn new words.
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Title: Transparent multijunction organic photovoltaics
Creator: Young, Margaret (Process engineer)
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "The widespread adoption of conventional solar cells based on inorganic semiconductors has been gaining traction in recent years but is still often hindered by high cost and lack of aesthetic appeal. Transparent organic semiconductor-based solar cells that selectively absorb in the UV and the NIR enable integration into building windows, automobiles, and consumer electronics in ways that traditional solar cells cannot. Moreover, integration onto existing infrastructure reduces the racking and...
Show more"The widespread adoption of conventional solar cells based on inorganic semiconductors has been gaining traction in recent years but is still often hindered by high cost and lack of aesthetic appeal. Transparent organic semiconductor-based solar cells that selectively absorb in the UV and the NIR enable integration into building windows, automobiles, and consumer electronics in ways that traditional solar cells cannot. Moreover, integration onto existing infrastructure reduces the racking and installation cost. In this work, we investigate routes to improve the efficiency of transparent solar cells by utilizing multijunction architectures. A transfer-matrix optical interference model is developed as a framework to optimize the full device stack considering the angle-dependent PV performance that is critical for matching subcell photocurrents in series tandem solar cells. In addition, a new method of fine tuning energy levels of low-bandgap small molecules with infrared selective absorption was demonstrated using a series of organic heptamethine salts. By exchanging the counterion from a small, hard anion to a fluorinated weakly coordinating anion, the frontier energy of the salt is shown to shift without affecting the bandgap, thus enabling simultaneous optimization of photocurrent generation of photovoltage. We further utilize this tunability to develop heptamethine molecules with absorption as deep as 1600 nm, the deepest infrared photo-response demonstrated to date with organic small molecules ideal for multijunction integration. Ultimately, transparent solar cells are an exciting new paradigm for solar deployment enabled by organic and excitonic semiconductors that offer a pathway to integrate solar onto virtually any surface without impacting the view."--Page ii.
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Title: Microwave Imaging Using a Tunable Reflectarray Antenna and Superradiance in Open Quantum Systems
Creator: Tayebi, Amin
Date: 2017
Collection: Electronic Theses & Dissertations
Description: Theory, experiment, and computation are the three paradigms for scientific discoveries. This dissertation includes work in all three areas. The first part is dedicated to the practical design and development of a microwave imaging system, a problem mostly experimental and computational in nature. The second part discusses theoretical foundations of possible future advances in quantum signal transmission. In part one, a new active microwave imaging system is proposed. At the heart of this...
Show moreTheory, experiment, and computation are the three paradigms for scientific discoveries. This dissertation includes work in all three areas. The first part is dedicated to the practical design and development of a microwave imaging system, a problem mostly experimental and computational in nature. The second part discusses theoretical foundations of possible future advances in quantum signal transmission. In part one, a new active microwave imaging system is proposed. At the heart of this novel system lies an electronically reconfigurable beam-scanning reflectarray antenna. The high tuning capability of the reflectarray provides a broad steering range of +\- 60 degrees in two distinct frequency bands: S and F bands. The array, combined with an external source, dynamically steers the incoming beam across this range in order to generate multi-angle projection data for target detection. The collected data is then used for image reconstruction by means of time reversal signal processing technique. Our design significantly reduces cost and operational complexities compared to traditional imaging systems. In conventional systems, the region of interest is enclosed by a costly array of transceiver antennas which additionally requires a complicated switching circuitry. The inclusion of the beam scanning array and the utilization of a single source, eliminates the need for multiple antennas and the involved circuitry. In addition, unlike conventional setups, this system is not constrained by the dimensions of the object under test. Therefore the inspection of large objects, such as extended laminate structures, composite airplane wings and wind turbine blades becomes possible. Experimental results of detection of various dielectric targets as well as detecting anomalies within them, such as defects and metallic impurities, using the imaging prototype are presented.The second part includes the theoretical consideration of three different problems: quantum transport through two different nanostructures, a solid state device suitable for quantum computing and spherical plasmonic nanoantennas and waveguides. These three physically different systems are all investigated within a single quantum theory; the effective non-Hermitian Hamiltonian framework. The non-Hermitian Hamiltonian approach is a convenient mathematical formalism for the description of open quantum systems. This method based on the Feshbach projection formalism provides an alternative to popular methodssuch as the Feynman diagrammatic techniques and the master equation approach that are commonly used for studying open quantum systems. It is formally exact but very flexible and can be adjusted to many specific situations. One bright phenomenon emerging in the situation with a sufficiently strong continuum coupling in the case when the number of open channels is relatively small compared to the number of involved intrinsic states is the so-called superradiance. Being an analog of superradiance in quantum optics, this term stands for the formation in the system of a collective superposition of the intrinsic states coherently coupled to the same decay channel. The footprint of superradiance in each system is investigated in detail. In the quantum transport problem, signal transmission is greatly enhanced at the transition to superradiance. In the proposed solid state based charge qubit, the superradiant states effectively protect the remaining internal states from decaying into the continuum and hence increase the lifetime of the device. Finally, the superradiance phenomenon provides us a tool to manipulate light at the nanoscale. It is responsible for the existence of modes with distinct radiation properties in a system of coupled plasmonic nanoantennas: superradiant states with enhanced and dark modes with extremely damped radiation. Furthermore, similar to the quantum case, energy transport through a plasmonic waveguide is greatly enhanced.
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Title: A detailed study of the gamma-ray nova V1324 Sco
Creator: Finzell, Thomas Michael Broen
Date: 2017
Collection: Electronic Theses & Dissertations
Description: It has recently been discovered that some, if not all, classical novae emit GeV gamma-rays, but the mechanisms involved in the production of the gamma-rays are still not well understood. We present here a comprehensive, multi-wavelength dataset---from radio to X-rays---for the most gamma-ray luminous classical nova to-date, V1324 Sco. Using this dataset, we show that V1324 Sco is a canonical dusty Fe-II type nova, with a reddening of E(B-V) = 1.16 +\- 0.12, a distance > 6.5 kpc, a bulk ejecta...
Show moreIt has recently been discovered that some, if not all, classical novae emit GeV gamma-rays, but the mechanisms involved in the production of the gamma-rays are still not well understood. We present here a comprehensive, multi-wavelength dataset---from radio to X-rays---for the most gamma-ray luminous classical nova to-date, V1324 Sco. Using this dataset, we show that V1324 Sco is a canonical dusty Fe-II type nova, with a reddening of E(B-V) = 1.16 +\- 0.12, a distance > 6.5 kpc, a bulk ejecta velocity of 1150 +/- 40 km/s and an ejecta mass of 2.0 +\- 0.4 * 10^-5 M_{Solar}. However, despite its seeming normalcy, there is also evidence for complex shock interactions, including the aforementioned gamma-rays and early time high-brightness temperature radio emission. To explain how a nova can be simultaneously ordinary and have the highest gamma-ray luminosity to date, we present a simplified model of the ejecta in which the strength of gamma-ray emission is set by properties of a fast ejecta component that collides with a slower component to produce shocks. We conclude this detailed study of V1324 Sco by showing how it has helped shape our understanding of the role of shocks in novae. Along with the study of V1324 Sco, this work also presents detailed methods for determining the reddening, distance, and filling factor of a classical nova from optical spectroscopy (using V1324 Sco as an example). We also provide detailed derivations for fitting nova radio light curves, to determine ejecta mass and velocity.
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Title: Flexible hierarchical Bayesian modeling extensions to improve whole genome prediction and genome wide association analyses
Creator: Chen, Chunyu (Graduate of Michigan State University)
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "Whole genome prediction (WGP) has been widely implemented in animal and plant breeding for genomic selection of economically important traits, having already accelerated genetic progress for economically important traits in some species especially dairy cattle. Genome wide association (GWA) analysis is used for screening genomic regions that may include important candidate genes segregating for the trait of interest and is being increasingly integrated with WGP analysis. Both WGP and GWA...
Show more"Whole genome prediction (WGP) has been widely implemented in animal and plant breeding for genomic selection of economically important traits, having already accelerated genetic progress for economically important traits in some species especially dairy cattle. Genome wide association (GWA) analysis is used for screening genomic regions that may include important candidate genes segregating for the trait of interest and is being increasingly integrated with WGP analysis. Both WGP and GWA typically represent m226Bn problems as defined by a large number of single nucleotide polymorphism (SNP) markers (m) and comparably much smaller number of individuals (n). Two broad types of parametric models are typically considered for these analyses: traditional best linear unbiased prediction approaches based on SNP marker effects being normally distributed and Bayesian WGP models that allow more flexible specifications for SNP marker effects based on either heavy-tailed or variable selection specifications. Bayesian WGP models can achieve higher prediction accuracies than traditional approaches in many applications if properly tuned; however, their implementation can be computationally challenging. My dissertation was aimed to address some of these emerging issues in Bayesian WGP models as well as providing software tools for real data applications. In Chapter 2, I developed an expectation maximization (EM) algorithm as a fast alternative to traditional Markov Chain Monte Carlo (MCMC) for Bayesian WGP models. I proposed EM implementations for two models, heavy-tailed BayesA and stochastic search and variable selection (SSVS) adapting the EM algorithm for maximum a posterior (MAP) inference of SNP effects and adapting REML like strategies to estimate key hyperparameters. Using a comprehensive simulation study and real data analysis, I found that these empirical Bayes approaches can be quite sensitive to starting values for SNP effects. However, using a deterministic annealing variant of EM, I obtained hyperparameter estimates and prediction accuracies comparable to their MCMC counterparts. In Chapter 3, I further assessed the possibility using two Bayesian WGP models BayesA and SSVS for GWA studies. I also included a popular GWA analysis (EMMAX) based on the utilization of the linear mixed model. In addition to basing inferences on traditional single SNP tests and fixed genomic window tests, I assessed the merit of tests involving adaptively determined windows based on clustering genome into blocks based on linkage disequilibrium. I found that SSVS and BayesA under MCMC and adaptive window tests led to best receiver operating curve (ROC) properties. In Chapter 4, I extended SSVS to single step SSVS to incorporate phenotypes of non-genotyped individuals and compared its performance with corresponding models ignoring these genotypes for both WGP and GWA. I found single step SSVS to be a promising for WGP and GWA, particularly for genetic architectures characterized by a few genes with large effects. In Chapter 5, I combined much of the developments in Chapter 2 to Chapter 4 and beyond in a unified framework as an open source R package BATools to implement several different Bayesian models for WGP and GWA."--Pages ii-iii.
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Title: Three dimensional analysis of the gas flow in piston ring pack
Creator: Kharazmi, Ali
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "Cylinder-kit dynamics design in an internal combustion engine is highly relevant for the engine performance characteristics, durability and reliability. Since the middle of the 20th century, researchers have been using numerical models to describe the processes that occur in a ring pack. Because it is difficult and extremely costly to conduct experiments on every series of engines to check for the blow-by and oil consumption, a computational analysis can be performed on the ring pack to...
Show more"Cylinder-kit dynamics design in an internal combustion engine is highly relevant for the engine performance characteristics, durability and reliability. Since the middle of the 20th century, researchers have been using numerical models to describe the processes that occur in a ring pack. Because it is difficult and extremely costly to conduct experiments on every series of engines to check for the blow-by and oil consumption, a computational analysis can be performed on the ring pack to study the blow-by and oil-consumption characteristics. In this dissertation a 3D CFD simulation model is introduced to analyze the flow between the cylinder liner and the piston. This model allows for calculation of the piston assembly with consideration of the ring dynamics, transient boundary conditions for combustion chamber pressure and temperature as well as thermal distortion of the piston and liner. The determination of the complex geometry of the cylinder-kit is established in a STL (STereoLithography) format by considering the complicated geometrical details of the ring pack such as thermal distortion of piston and liner, ring twist and ring/groove conformability. The blow by and blow back is numerically calculated for a small bore cylinder operating at 2000 RPM and verified by the results of commercially available 1D models. The calculated velocity filed shows substantial circumferential flow in the piston ring pack that is dominated by the ring and groove geometry as well as the relative position of the rings end gap. It is found that the amount of gas that flows back to the combustion chamber increases when the in-cylinder pressure trace decreases from its peak value. The knowledge from this study can be used as a basis for further multiphase calculations containing oil flow such as oil consumption, oil evaporation and eventually cylinder-kit wear."--Page ii.
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Title: Balancing convergence and diversity in evolutionary single, multi and many objectives
Creator: Seada, Haitham
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "Single objective optimization targets only one solution, that is usually the global optimum. On the other hand, the goal of multiobjective optimization is to represent the whole set of trade-off Pareto-optimal solutions to a problem. For over thirty years, researchers have been developing Evolutionary Multiobjective Optimization (EMO) algorithms for solving multiobjective optimization problems. Unfortunately, each of these algorithms were found to work well on a specific range of objective...
Show more"Single objective optimization targets only one solution, that is usually the global optimum. On the other hand, the goal of multiobjective optimization is to represent the whole set of trade-off Pareto-optimal solutions to a problem. For over thirty years, researchers have been developing Evolutionary Multiobjective Optimization (EMO) algorithms for solving multiobjective optimization problems. Unfortunately, each of these algorithms were found to work well on a specific range of objective dimensionality, i.e. number of objectives. Most researchers overlooked the idea of creating a cross-dimensional algorithm that can adapt its operation from one level of objective dimensionality to the other. One important aspect of creating such algorithm is achieving a careful balance between convergence and diversity. Researchers proposed several techniques aiming at dividing computational resources uniformly between these two goals. However, in many situations, only either of them is difficult to attain. Also for a new problem, it is difficult to tell beforehand if it will be challenging in terms of convergence, diversity or both. In this study, we propose several extensions to a state-of-the-art evolutionary many-objective optimization algorithm - NSGA-III. Our extensions collectively aim at (i) creating a unified optimization algorithm that dynamically adapts itself to single, multi- and many objectives, and (ii) enabling this algorithm to automatically focus on either convergence, diversity or both, according to the problem being considered. Our approach augments the already existing algorithm with a niching-based selection operator. It also utilizes the recently proposed Karush Kuhn Tucker Proximity Measure to identify ill-converged solutions, and finally, uses several combinations of point-to-point single objective local search procedures to remedy these solutions and enhance both convergence and diversity. Our extensions are shown to produce better results than state-of-the-art algorithms over a set of single, multi- and many-objective problems."--Pages ii-iii.
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Title: Modelling and control of a turbocharged diesel engine
Creator: Zeng, Tao, (Graduate of Michigan State University)
Date: 2017
Collection: Electronic Theses & Dissertations
Description: The diesel engine is known for its high efficiency, performance, and durability. With stringent fuel economy and emission regulations, diesel engines face increasing challenges. To accommodate emission regulations, fuel economy and performance requirements, modern diesel engines are equipped with the variable geometry turbocharger (VGT) and exhaust gas recirculation (EGR) system. VGT extracts energy from the exhaust gas to drive the compressor to improve transient response, steady-state...
Show moreThe diesel engine is known for its high efficiency, performance, and durability. With stringent fuel economy and emission regulations, diesel engines face increasing challenges. To accommodate emission regulations, fuel economy and performance requirements, modern diesel engines are equipped with the variable geometry turbocharger (VGT) and exhaust gas recirculation (EGR) system. VGT extracts energy from the exhaust gas to drive the compressor to improve transient response, steady-state performance, and fuel efficiency under a wide range of engine flow conditions. Meanwhile, EGR dilutes fresh air with exhaust gas to reduce the formation of mono-nitrogen oxides NO and NO2 (NOx). The VGT and EGR control design is complicated due to the natural coupling between VGT and EGR, and high nonlinearity of diesel engine air-path system. The extra assisted power and regenerative power on the turbocharger shaft further increase the control system complexity. In this dissertation, new approaches for turbocharger system modelling and multivariable control design for the coordinated actuation of the VGT-EGR system are investigated. The control design is further extended to hydraulic regenerative assisted turbocharger system.New modelling approaches for turbocharger system are proposed based on turbomachinery physics. Proposed turbine and compressor models eliminate the interpolation error, and especially, allow smooth extrapolation outside the mapped region. A high fidelity reduced order mean value model of a diesel engine for automotive application is developed based on developed turbocharger model. Further, new models for high-speed hydraulic turbines and centrifugal pumps are developed for hydraulic assisted and regenerative turbochargers.A regenerative hydraulic assisted turbocharger (RHAT) system is investigated in this dissertation. A system level approach based on 1-D simulations is used to understand the assist benefits and design trade-offs. Simulation results show that 3-5% fuel economy improvement for FTP 75 driving cycle, depending on different sub-component sizing. The study also identifies technical challenges for optimal design and control of RHAT systems.A linear controller design approach is proposed in this dissertation for regulating both boost pressure and EGR mass flow rate of the VGT-EGR system. The linear quadratic control with integral action is designed based on the linearized system. Local controllers are scheduled based on engine operational parameter: engine speed and fuel injection quantity. The gain scheduled liner controller is validated against baseline controller based on the nonlinear plant. Results show that designed multi-input and multi-output (MIMO) controller can well manage the trade-offs between boost pressure tracking and EGR mass flow tracking, compared to baseline controller (two single input single output (SISO) controllers). A novel approach is proposed for closed-loop control design with respect to engine performance and engine emission trade-offs. The controller design is further extended to assisted and regenerative turbocharger system with VGT and EGR. The results show that emission reduction, engine performance and fuel economy improvement can be achieved at the same time with external power applied to the turbocharger shaft.
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Title: Hardware algorithms for high-speed packet processing
Creator: Norige, Eric
Date: 2017
Collection: Electronic Theses & Dissertations
Description: The networking industry is facing enormous challenges of scaling devices to support theexponential growth of internet traffic as well as increasing number of features being implemented inside the network. Algorithmic hardware improvements to networking componentshave largely been neglected due to the ease of leveraging increased clock frequency and compute power and the risks of implementing complex hardware designs. As clock frequencyslows its growth, algorithmic solutions become important...
Show moreThe networking industry is facing enormous challenges of scaling devices to support theexponential growth of internet traffic as well as increasing number of features being implemented inside the network. Algorithmic hardware improvements to networking componentshave largely been neglected due to the ease of leveraging increased clock frequency and compute power and the risks of implementing complex hardware designs. As clock frequencyslows its growth, algorithmic solutions become important to fill the gap between currentgeneration capability and next generation requirements. This paper presents algorithmicsolutions to networking problems in three domains: Deep Packet Inspection(DPI), firewall(and other) ruleset compression and non-cryptographic hashing. The improvements in DPIare two-pronged: first in the area of application-level protocol field extraction, which allowssecurity devices to precisely identify packet fields for targeted validity checks. By usingcounting automata, we achieve precise parsing of non-regular protocols with small, constantper-flow memory requirements, extracting at rates of up to 30gbps on real traffic in softwarewhile using only 112 bytes of state per flow. The second DPI improvement is on the longstanding regular expression matching problem, where we complete the HFA solution to theDFA state explosion problem with efficient construction algorithms and optimized memorylayout for hardware or software implementation. These methods construct automata toocomplex to be constructed by previous methods in seconds, while being capable of 29gbpsthroughput with an ASIC implementation. Firewall ruleset compression enables more firewall entries to be stored in a fixed capacity pattern matching engine, and can also be usedto reorganize a firewall specification for higher performance software matching. A novelrecursive structure called TUF is given to unify the best known solutions to this problemand suggest future avenues of attack. These algorithms, with little tuning, achieve a 13.7%improvement in compression on large, real-life classifiers, and can achieve the same results asexisting algorithms while running 20 times faster. Finally, non-cryptographic hash functionscan be used for anything from hash tables to track network flows to packet sampling fortraffic characterization. We give a novel approach to generating hardware hash functionsin between the extremes of expensive cryptographic hash functions and low quality linearhash functions. To evaluate these mid-range hash functions properly, we develop new evaluation methods to better distinguish non-cryptographic hash function quality. The hashfunctions described in this paper achieve low-latency, wide hashing with good avalanche anduniversality properties at a much lower cost than existing solutions.
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Title: Cardiovascular system modeling : arterial growth and remodeling
Creator: Tilahun, Hailu Getachew
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "Vascular systems in the human blood circulation regulate their environment when there are alterations of hemodynamic loading from homeostatic levels, depending on the magnitude and the duration of the changes. The main focus of this work is to develop a bio-chemo-mechanical model of arterial growth and remodeling wherein changes in blood pressure and flow are sustained over weeks or months. Using a two-step kinetic reaction model of collagen, which is the dominant structural protein in...
Show more"Vascular systems in the human blood circulation regulate their environment when there are alterations of hemodynamic loading from homeostatic levels, depending on the magnitude and the duration of the changes. The main focus of this work is to develop a bio-chemo-mechanical model of arterial growth and remodeling wherein changes in blood pressure and flow are sustained over weeks or months. Using a two-step kinetic reaction model of collagen, which is the dominant structural protein in arteries, as a function of arterial wall stress changes, we track and evaluate the temporal change in mass deposition and degradation of extracellular matrix. We employ a constrained mixture model to capture the response of the artery to hemodynamic loadings, leading to strain energy changes that depend on the stiffness and relative mass ratio of the constituents of the artery. In so doing, we investigate the temporal changes of the geometry of the artery over weeks and months. We also explore the possible ranges of the collagen turnover rates, the coupling between collagen turnover and stresses, and the length of time it takes for the vascular stresses to return back to the steady homeostatic states while the artery is still under sustained loadings. The developed mathematical models are verified by previously published mathematical models and validated by comparing the mathematical result with animal experiments. Using reported experimental data, we inversely compute the arterial constituent mass turnover. After minimizing the total error between the simulated and experimental arterial thickness values, parameters such as collagen and smooth muscles degradation rates are estimated. The efficiency of computation is improved by singular value decomposition and regularization. We also study a lumped whole body model in the cardiovascular system with baroreflex. In this model, we incorporate the effect of arteriovenous fistula and can get verifiable results as per reported vascular maturation data."--Pages ii-iii.
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Title: Why not academia?---The streamlined career choice process of Black African women engineers : a grounded theory study
Creator: Mlambo, Yeukai Angela
Date: 2017
Collection: Electronic Theses & Dissertations
Description: Black African women are grossly underrepresented as academic staff in engineering programs at South African universities. The problem is exacerbated at historically White institutions (HWI) where Black women are simply absent as engineering research and teaching staff. The absence of Black African women in the academy occurs despite Black African women enrolling and graduating with engineering postgraduate degrees making them eligible for academic jobs. Furthermore, despite Black African...
Show moreBlack African women are grossly underrepresented as academic staff in engineering programs at South African universities. The problem is exacerbated at historically White institutions (HWI) where Black women are simply absent as engineering research and teaching staff. The absence of Black African women in the academy occurs despite Black African women enrolling and graduating with engineering postgraduate degrees making them eligible for academic jobs. Furthermore, despite Black African women representing the largest population in South Africa at 41% of the population overall, and affirmative action policies in place, engineering academic spaces remain predominantly White and male, not representative of the country's population. In fact White women are overrepresented in engineering academe and in some cases White women are the only female presence in engineering higher education employment. If Black African women are graduating with engineering degrees why are they not equally represented in engineering academe as their White female counterparts? How can the absence of Black African women engineering academics be explained? I use Charmaz's constructivist grounded theory (CGT) to understand the career choice processes of Black African engineering alumni women in South Africa to explain why their career choices thus far have not included the academy. Approaching the research from a social constructivist paradigm, loosely guided by a conceptual framework of African feminism(s) and CGT, and borrowing from life history interview methods this study addresses the underrepresentation of Black African women in engineering academe. Findings indicate Black African women's career choices in engineering are driven by prospects of socio-economic mobility and family/community responsibilities, a product of historical circumstances during apartheid that created social inequalities with Black families relegated to lower socio-economic statuses. In this study career choices were heavily influenced by teachers in pre-tertiary schooling, student academic competencies in mathematics and science, and industry practices that included providing bursary funds to only support engineering higher education endeavors, thereby dictating to students from low income households which careers to pursue especially in cases where the absence of such funding meant one would not be able to afford university costs. The academy was not viewed as a place of work seen instead as a transitory space. The image of the academy as made up of older White males also created the perception that it was not a place for Black women. The combination of the factors influencing career choices in school and the image of the academy as an unwelcoming space for Black women explains Black women's absence in South African engineering academia. Postsecondary institutional leaders should work on changing the image of the academy and marketing it as a career option for students in pre-tertiary and postsecondary education. Institutional culture and representation needs to reflect the diverse student population while actively working to ensure all students, academic and administrative staff feels welcome and valued. More importantly financial resources need to be made available and leveraged to support Black African women's education in a bursary-style format to encourage more Black women to follow academic career pathways.
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Title: Numeracy, severity, and communicating risk : perceptions of prescription pain medication side effects
Creator: Cox, Jeffrey G. (Jeffrey George)
Date: 2017
Collection: Electronic Theses & Dissertations
Description: This dissertation reports on a study that explored how individuals interpret and quantify verbal descriptions of the risk of side effects from a hypothetical prescription pain medication, as well as what factors affect these interpretations. While the European Union has set out recommendations for how these terms quantifiers (e.g., "very rare," "common") should be interpreted, studies (Cox, 2016; Berry, Knapp, & Raynor, 2002; Knapp, Raynor, & Berry, 2004) indicate that individuals...
Show moreThis dissertation reports on a study that explored how individuals interpret and quantify verbal descriptions of the risk of side effects from a hypothetical prescription pain medication, as well as what factors affect these interpretations. While the European Union has set out recommendations for how these terms quantifiers (e.g., "very rare," "common") should be interpreted, studies (Cox, 2016; Berry, Knapp, & Raynor, 2002; Knapp, Raynor, & Berry, 2004) indicate that individuals dramatically overestimate these effects' likelihood. Situated within fuzzy trace theory (Reyna & Brainerd, 1995) the present study assessed how individuals quantify these terms, as well as what internal (e.g., numeracy, existing perceptions of prescription pain medications) and external (e.g., verbal quantifiers used, severity of side effect) factors influence their gist and verbatim processing of risk information. The study used a between-subjects experimental design: 2 ("common"/"rare") X 2 (adverb/no adverb) X 2 (severity) embedded within an online survey about impressions of prescription pain medications. Findings reveal that individuals' existing, general perceptions of prescription pain medications have a larger impact on their gist perceptions than their verbatim ones, while their estimates are significantly higher than experts' recommendations. Important differences between the subjective and objective numeracy scales are also found for participants' confidence in their numerical estimates. Other findings related to the study of risk perceptions, as well as implications for practice and policy, are discussed.
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Title: New routes to the African diaspora(s : locating 'Naija' identities in transnational cultural productions
Creator: Nwabara, Olaocha Nwadiuto
Date: 2017
Collection: Electronic Theses & Dissertations
Description: Nigerian American Yvonne Orji–star of HBO Series Insecure–shared her self-defined expressions of her Nigerian Diaspora aka 'Naija' identity at a Breakfast Club online interview. She demonstrated her negotiation of her Nigerian and Black American identity, and in doing so reveals the multiplicity of her Black identity. The Nigerian Diaspora is increasingly producing normalized tropes in global Black popular culture, such as formulations of the Nigerian film industry, Nollywood, and...
Show moreNigerian American Yvonne Orji–star of HBO Series Insecure–shared her self-defined expressions of her Nigerian Diaspora aka 'Naija' identity at a Breakfast Club online interview. She demonstrated her negotiation of her Nigerian and Black American identity, and in doing so reveals the multiplicity of her Black identity. The Nigerian Diaspora is increasingly producing normalized tropes in global Black popular culture, such as formulations of the Nigerian film industry, Nollywood, and transnational music in the Afrobeat and Naija Mix genres. Cultural productions that come from these and other Nigerian cultural industries are being created and represented by members of the Nigerian "cultural" Diaspora all over the world. These cultural representations are mapped onto cultural artifacts (e.g. film, music, literature, television, food, clothing) are reflected back into diasporic communities when accepted by its members as having meaning and telling stories of their everyday experiences. Works like these are constitutive of a growing cohort and body of cultural productions emerging from the African Diaspora in the post-colonial era. Examples examined in the current dissertation study include the now famous Nigerian Diaspora representations conveyed in cultural productions such as Chimamanda Ngozi Adichie's Americanah, rapper Wale's "My Sweetie" and "The God Smile," Yewande Omotoso's Bom Boy, Akin Omotoso's Man on Ground, and Adze Ugah's Jacob's Cross to name a few. This dissertation is situated within the growing scholarly discourse about new African Diasporas through the prism of cultural diasporas. To guide the study theoretically, I draw from African Diaspora theorists such as Kim Butler, Isidore Okpewho, Paul Zeleza, Juan Flores, and Ruth Simms Hamilton as well as from Cultural Studies theorists Stuart Hall and Pierre Bourdieu to examine select Nigerian artists, their productions, and subsequent representations in the Nigerian Diaspora as cultural diasporas. I present these cultural productions of Nigerian diasporas as a way of examining the transformative and transnational identities (i.e. racial, ethnic, cultural) and community formations that are forged in the dialectical relationship between African homelands (Nigeria) and African Diaspora hostlands (the US and South Africa). In this dissertation, I argue that the social construction of the core identity formation of Nigerian Diasporas (Naija) has a purposeful and useful function for Nigeria in the world through its migrants Diaspora hostlands. The study shows the Nigerian Diaspora identity in this regard acknowledges and unifies Nigerians wherever they may be in the world and allows them to asserts an emotional attraction and belonging to the Nigerian homeland. The social construction of 'Naija' is used in this study as prism for interrogating issues facing Nigerian people in their respective diasporas, while also revealing the distinctive cultural life-styles that Nigerian Black immigrants bring and contribute to their hostlands. The research design focuses in on those primary components of the cultural diasporas–the experiences of the cultural producers (interviews and public talks) and the analysis of their cultural productions (literature, film, television, YouTube, music)–in order to extrapolate cultural representations of the Nigerian Diaspora communities in the United States and South Africa. The study aims to use this data to significantly contribute perspectives of how Nigerian Diasporic cultural identities and experiences are self-represented and exerted in global Diasporic communities, specifically in the racially and ethnic diverse nations of the United States and South Africa. Further, the dissertation examines how representations of self and community becomes decolonial tools for defining and asserting complex Black Diasporic identities and cultural formations.
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Title: Information, knowledge, and demand for substitute health inputs : experimental evidence of pesticide use in Zambia
Creator: Goeb, Joseph Christopher
Date: 2017
Collection: Electronic Theses & Dissertations
Description: ABSTRACTINFORMATION, KNOWLEDGE, AND DEMAND FOR SUBSTITUTE HEALTH INPUTS: EXPERIMENTAL EVIDENCE OF PESTICIDE USE IN ZAMBIAByJoseph Christopher GoebMany goods carry health risks that have important impacts on demand and behavior. However, the risks are rarely transparent and, as a result, consumers often have incomplete knowledge of the health risks associated with many of their consumption decisions. This can lead to inefficient behavior. With that in mind, economists have studied the impacts...
Show moreABSTRACTINFORMATION, KNOWLEDGE, AND DEMAND FOR SUBSTITUTE HEALTH INPUTS: EXPERIMENTAL EVIDENCE OF PESTICIDE USE IN ZAMBIAByJoseph Christopher GoebMany goods carry health risks that have important impacts on demand and behavior. However, the risks are rarely transparent and, as a result, consumers often have incomplete knowledge of the health risks associated with many of their consumption decisions. This can lead to inefficient behavior. With that in mind, economists have studied the impacts of risk information on consumer behavior, though the effects are rarely straightforward as there may be risk compensation and substitution effects across inputs and behaviors. This dissertation tests the effects of information on knowledge and demand for two substitute health inputs using a randomized control trial of pesticide users in rural Zambia.Essay 1 contributes to the broader literature on information, knowledge, and preventative health demands, and to the pesticide safety literature by presenting the first randomly controlled test of the impacts of pesticide safety information on willingness-to-pay (WTP) for personal protective equipment (PPE) measured using two Becker-DeGroot-Marschak mechanisms. Despite knowledge improvements from the training, overall effects on demand for PPE were insignificant. We also find that demand for both gloves and masks is highly elastic near their market prices.Essay 2 shows that information significantly changed pesticide choices, which were assessed using stated choice experiments and actual purchase decisions before and after the information intervention. We find that farmers held an erroneous positive price-quality perception for pesticides prior to receiving information, and that information effectively broke that perception. Importantly for health, farmers chose less toxic pesticides more often after receiving information on relative toxicities and health risks. Essay 3 presents a detailed assessment of farmer pesticide knowledge using 22 questions covering pesticide control properties and health risks. We find that Zambian tomato farmers generally know pesticides are harmful to their health, but they lack product-specific knowledge on pesticide toxicity and pesticide control properties. The training program caused an increase in overall pesticide knowledge with large increases in toxicity knowledge, pest control knowledge, and pesticide efficacy knowledge. The effects of information on protective equipment knowledge were insignificant.
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Title: Self-directed learning through the eyes of a Buddhist meditator : (non)control, (non)becoming, and (non)judgement
Creator: Nguyen, Cuong Huy
Date: 2017
Collection: Electronic Theses & Dissertations
Description: By using the meditative inquiry approach, I compare and contrast the philosophy underlying Buddhist meditation, based on my personal experiences with and scholarship on the mindfulness practice, with self-directed learning within the tradition of progressive education, based on the case study of the Jefferson County Open School, a progressive school in Lakewood (CO, USA). I found that Buddhist meditation and self-directed learning have a lot in common. In particular, they both emphasize (non...
Show moreBy using the meditative inquiry approach, I compare and contrast the philosophy underlying Buddhist meditation, based on my personal experiences with and scholarship on the mindfulness practice, with self-directed learning within the tradition of progressive education, based on the case study of the Jefferson County Open School, a progressive school in Lakewood (CO, USA). I found that Buddhist meditation and self-directed learning have a lot in common. In particular, they both emphasize (non)control, (non)becoming, and (non)judgement. As a meditative inquiry, this study has brought about a lot of profound inner transformation in terms of both spirituality and philosophy of education, which are explicitly presented in this dissertation.
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Title: Volumes, determinants, and meridian lengths of hyperbolic links
Creator: Burton, Stephan D., 1987-
Date: 2017
Collection: Electronic Theses & Dissertations
Description: We study relationships between link diagrams and link invariants arising from hyperbolic geometry. The volume density of a hyperbolic link K is defined to be the ratio of the hyperbolic volume of K to the crossing number of K. We show that there are sequences of non-alternating links with volume density approaching v_8, where v_8 is the volume of the regular ideal hyperbolic octahedron. We show that the set of volume densities is dense in [0,v_8]. The determinant density of a link K is 2 pi...
Show moreWe study relationships between link diagrams and link invariants arising from hyperbolic geometry. The volume density of a hyperbolic link K is defined to be the ratio of the hyperbolic volume of K to the crossing number of K. We show that there are sequences of non-alternating links with volume density approaching v_8, where v_8 is the volume of the regular ideal hyperbolic octahedron. We show that the set of volume densities is dense in [0,v_8]. The determinant density of a link K is 2 pi log det(K)/c(K). We prove that the closure of the set of determinant densities contains the set [0, v_8]. We examine the conjecture, due to Champanerkar, Kofman, and Purcell that vol(K) < 2 pi log det (K) for alternating hyperbolic links, where vol(K) = vol(S^3\ K) is the hyperbolic volume and det(K) is the determinant of K. We prove that the conjecture holds for 2-bridge links, alternating 3-braids, and various other infinite families. We show the conjecture holds for highly twisted links and quantify this by showing the conjecture holds when the crossing number of K exceeds some function of the twist number of K.We derive bounds on the length of the meridian and the cusp volumeof hyperbolic knots in terms of the topology of essential surfaces spanned by the knot.We provide an algorithmically checkable criterion that guarantees that the meridian length of a hyperbolic knot is below a given bound.As applications we find knot diagrammatic upper bounds on the meridian length and the cusp volume of hyperbolic adequate knots and we obtain new large families of knots withmeridian lengths bounded above by four. We also discuss applications of our results to Dehn surgery.
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Title: Internationalizing graduate education through education abroad : the pedagogy of short-term, faculty-led, education abroad experiences
Creator: Loebick, Karla
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "The purpose of this study was to develop understanding of the perspectives of faculty members as leaders of short-term, faculty-led, education abroad at the graduate level ... " Abstract.

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