Digital Commons Network^™

Enzymatic Inhibition By Lignin During Second Generation Ethanol Production, Antonio Carlos Freitas Dos Santos

Open Access Dissertations

An important hindrance to commercialization of lignocellulosic ethanol is the high cost of enzymes. Reducing enzyme loadings is necessary to reduce costs. Knowledge of the inhibitors of these enzymes is necessary to better inform enzyme development and process design. Five factors have been identified: soluble inhibitors, solid lignin adsorption, product inhibition, mixing efficiency and oxygen deactivation of the enzymes that hydrolyze cellulose to glucose. These factors are intertwined and properly assessing them individually require the elimination of the others. Isolating each factor, however, has not been done throughout literature leading to lumped constants. Soluble inhibitors reduce conversion sharply leading to …

Polysulfide Mitigation At The Electrode-Electrolyte Interface: Experiments In Rechargeable Lithium Sulfur Batteries, Arthur D. Dysart

Open Access Dissertations

In the field of energy storage technology, the lithium sulfur battery is intensely studied in interest of its great theoretical gravimetric capacity (1672 Ah kg–1) and gravimetric density (2600 Wh kg–1). The theoretical performance values satisfy viability thresholds for petroleum–free electric vehicles and other emerging technologies. However, this elusive technology remains in the research sector due to a wealth of challenges resulting from its complex chalcogenide electrochemistry. The most infamous challenge remains the polysulfide redox shuttle, a phenomenon in which lithium polysulfide intermediates are produced as elemental sulfur S8 is reduced to lithium sulfide Li2S during the discharge cycle. Because …

The Theory And Practice Of Rhetorical Gaming For Composition Instruction, Jeffrey M. Gerding

Open Access Dissertations

In recent years videogames scholarship has grown from a small interest group within rhetoric and composition to a burgeoning interdisciplinary subfield. This growth has not been without problems or controversies, however, and on the whole there seems to be little consistency in either theory or practice when it comes to integrating games into composition curriculum. The purpose of this thesis is to examine a number of theories, concepts, procedures, and issues in the history of games and composition in order to suggest a possible direction for the future. To be clear, this is not an attempt to standardize a rule-governed …

Soundscape Ecology: Rich Contexts For Investigating Conservation Biology & The Effect Of Informal Environmental Experiences On Youth’S Conceptual Understanding, Interest And Identity Development, Maryam Ghadiri Khanaposhtani

Open Access Dissertations

Recent educational studies have shown increasing lack of interest and participation of youth (ages 10-14 years old) in various STEM (Science, Technology, Engineering and Mathematics) fields in the U.S. The decline in the number of youth choosing to study STEM fields in higher education and the resulting lack of STEM professionals in the society has drastic economic impacts. Therefore, it is critical to introduce youth to quality STEM education that engages them with science practices and triggers their interest and curiosity in order to increase their participation in those fields. To address this issue, the aim of this study is …

Characterizing Trade-Off Decisions In Student Designers, Molly Hathaway Goldstein

Open Access Dissertations

Decision-making and design in uncertain situations in which information is limited and goals are ambitious or conflicting are a part of common practices of engineers. Such abilities in engineering practices are important to develop for all students from elementary school through college and graduate school. An important aspect of decision-making in design are the trade-offs decisions designers make throughout a project. Trade-offs are a complex element of a decision, that involves weighing possible outcomes against their respective benefits and costs in areas such as aesthetics, cost, degree of safety, and various performance indicators. Making trade-off decisions is an effective design …

Digital Badges And Student Motivation In The Undergraduate Chemistry Laboratory, Sarah Hensiek

Open Access Dissertations

Laboratory courses have been the focus of much research and debate in the field of chemistry. One goal for the laboratory that is consistently cited by faculty is student learning of hands-on skills. Despite this, hands-on skills are rarely assessed in practice because to do so is resource intensive. Digital badges allow each individual student to demonstrate their proficiency in a hands-on lab skill while relieving the constraints associated with assessing individual students during a laboratory period. Previously at Purdue, digital badges were developed for the pipet, buret, and volumetric flask. These badges were shown to support student learning of …

An Examination Of Underrepresentation In Florida, Indiana, And Washington, Jaret Hodges

Open Access Dissertations

Black, Latinx, and Native American students are underrepresented in gifted education programs across the United States. This underrepresentation is one way in which the excellence gap manifests in gifted education. In turn, the underlying causes for underrepresentation are debated by scholars. This dissertation examines the issue of underrepresentation through three case studies. In all case studies, a generalized linear mixed model is used as the framework to analyze publicly available data acquired from the associated state departments of education.

The first case study examines underrepresentation in the state of Florida. In this study, the influence of socioeconomic status on rates …

A Spectroscopic Study Of The Folding Propensities Of Molecules Relevant In Combustion Processes, Daniel Malcolm Hewett

Open Access Dissertations

This thesis focuses on the conformational preferences of molecules relevant in combustion, specifically alkylbenzenes, present in diesel fuels, and covalently-bound naphthalene dimers, likely intermediates in the soot formation process. Utilizing a suite of conformation-specific laser techniques, coupled with a supersonic jet expansion to cool the molecules down to their ground state zero-point vibrational level, the infrared and ultraviolet spectra of individual conformers are collected and compared to theoretical predictions, resulting in conformational assignments.

The first section of this thesis discusses a series of straight chain alkylbenzenes, from ethylbenzene through dodecylbenzene, with the primary goal of determining the shortest chain length …

Limiting Mixed Hodge Theory And Nonabelian Hodge Theory For Nodal Curves, Feng Hao

Open Access Dissertations

This thesis contains two parts. In the first part, we will give the Deligne 1-motives up to isogeny corresponding to the Q-limit mixed Hodge structures of semi-stable degenerations of curves, using logarithmic structures and Steenbrink’s cohomological mixed Hodge complexes associated to semi-stable degenerations of curves. In the second part, we study the nonableian Hodge theory for nodal curves, construct a “Dolbeault moduli spaces” MDol(X,m) for Higgs bundles on nodal curves, and give the formality theorem for local systems and Higgs bundles on nodal curves. We also give some discussions on the Hitchin fibration of MDol(X,m) and the mixed Hodge structure …

Quantification Of Morphogen Gradients And Patterning Scale Invariance Along Dorsal-Ventral Embryonic Axis, Yan Huang

Open Access Dissertations

Morphogen gradients provide positional information to underlying cells that translate the information into differential gene expression and eventually different cell fates. Scale invariance is the property where the gradients of the morphogen adjust proportionately to the size of the domain. Scale invariance of morphogen gradients or patterns of differentiation is a common phenomenon observed between individuals within the same species and between homologous tissues or structures in different species. To determine whether a pattern is scale invariant, we and others developed definitions and measurements of gradient scaling. These include point-wise and global scaling errors as well as global scaling power. …

Pathways To Persistence: A Study Of The Effects Of Neighborhood Stress And Family Communication Patterns On Community College Student Outcomes, Jill Marie Inderstrodt

Open Access Dissertations

This dissertation draws upon literature from family communication, sociology, public health, and education to determine what neighborhood and family factors contribute to a community college student’s commitment to the goal of completing college. Community college students are more likely to come from low socioeconomic conditions, are more likely to have parents who did not earn a college degree, and are more likely to be ethnic or racial minorities than traditional four-year college students. Because of these demographics, community college students are also more likely to live in neighborhoods with high levels of neighborhood stress: noise and other pollution, crime, high …

Resource Allocation In Nanocommunication Networks And Online Service Platforms., Wei-Kang Hsu

Open Access Dissertations

Resource allocation appears in various forms in communication and networking systems. In this thesis, we start with relay-based nanonetwork communications and analyze the message delay with bacteria-inspired message transfer carriers. Modeling the message transfer as a renewal process, we draw the connection to the mobility model of ad-hoc networks and show that the expected message delay between two nodes is a convex function of the number of available carriers. We then design a decentralized carrier-allocation strategy such that the systematic message delay is minimized. We show that the proposed policy can effectively reduce weighted delays when different message priorities are …

Makerspaces For Education, Avneet Hira

Open Access Dissertations

In my dissertation, I present research examining Makerspaces for education. The concept of a Makerspace has evolved, currently being understood as a space for people to practice the idiomatic term Making, which is to tinker or fabricate. Broadly put, Makerspaces are environments where individuals use technologies to Make physical artifacts within a community of fellow Makers.

When I started this work, stakeholders from a variety of backgrounds had begun to discern the educational potential of Makerspaces. Since then, several resources in schools, libraries, educational research, and community spaces have been directed towards realizing this educational potential. However, despite the belief …

Performance Of Finned Heat Exchangers After Air-Side Fouling And Cleaning, Harshad V. Inamdar

Open Access Dissertations

Air-side fouling of enhanced surface heat exchangers by particulate matter may significantly reduce their performance. Hence, the effect of particulate fouling and subsequent cleaning on the performance of finned heat exchangers is investigated. It is anticipated that heat exchanger geometry and operating conditions such as air velocity, air humidity, and concentration of dust in air will impact the process of fouling and subsequent performance degradation of heat exchangers.

In the experimental phase of research, heat exchangers being tested are installed in a wind tunnel where all air-side parameters can be controlled. ASHRAE standard test dust is injected into the air …

Constructing Fragment-Density Functionals, Kaili Jiang

Open Access Dissertations

Approximations of the non-additive non-interacting kinetic energy (NAKE) as an explicit functional of the density are the basis of fragment-based methods that provide improved computational efficiency over standard Kohn-Sham calculations. However, within most fragment-based formalisms, there is no unique NAKE, making it difficult to develop general, robust approximations to it. In partition density-functional theory (P-DFT), the ambiguity of the NAKE is removed and approximate functionals may be more meaningfully compared to exact quantities. We demonstrate that the decomposable approximations constructed from approximations to the non-interacting kinetic energy fail to reproduce accurate NAKE and discuss promising avenues for constructing fragment density-functionals …

Revisiting The Decay Of Monochloramine, Utami Irawati

Open Access Dissertations

An aqueous solution containing predominantly monochloramine can be very complex chemically, as once it is formed, monochloramine can undergo a number of reactions. The loss of monochloramine primarily occurs through monochloramine hydrolysis or through a disproportionation reaction. However, there are only a few research papers that have investigated the kinetics of these two reactions. Some of the findings of these previous studies show inconsistencies with respect to the rate constant values of the reactions. Hence, both of these reactions were studied in depth in this work. In the case of the disproportion-ation reaction, previous studies have indicated that the presence …

A Multi-Agent Control Approach For Optimization Of Central Cooling Plants, Rita Jaramillo

Open Access Dissertations

This research focuses on the application of a multi-agent control approach to optimal supervisory control of central cooling systems. Most of the research related to supervisory control of central cooling systems has focused on centralized control approaches. Although these approaches can be effective at reducing operational costs, the high initial costs associated with site-specific controller design and implementation, and the need to update the plant model and control sequences every time a modification is made, have prevented a greater penetration of these technologies in the market. In light of these limitations, the goal of this research is the development and …

Essays On Labor Economics, Xuan Jiang

Open Access Dissertations

Quantum annealing (QA) uses the principles of quantum mechanics for solving unconstrained optimization problems. Since its initial proposal, there has been much interest in the search for practical problems for which QA has advantage over classical algorithms. Although it is believed that quantum computers cannot in general solve NP-complete problems effciently, there has been evidence suggesting that effects such as quantum tunneling can bring quantum speedup over classical computation for some problems in NP.

In this dissertation, we consider two problems that have both theoretical and practical importance. One is the Set Cover with Pairs problem. The other is the …

Refracting Gender: Experiences Of Transgender Students In Postsecondary Stem Education., Elizabeth Kersey

Open Access Dissertations

Transgender students are often an invisible minority in postsecondary education, particularly in STEM fields. I am addressing the lack of research in this area with an exploratory narrative study designed to answer two questions: (1) How have the experiences of postsecondary transgender students in STEM education varied with their gender presentation? (2) How do their experiences with mathematics compare with other STEM fields? I conducted a sequence of three interviews each with three participants to gather information about their life histories relating to gender and STEM. This information was then restoried utilizing the three-dimensional space of narrative inquiry proposed by …

Atomistic Simulations And Microscopic Experiments To Understand Nanoscale Composition Control, Changeun Kim

Open Access Dissertations

In this dissertation, the possibility of using the quantum mechanics calculation in combination with experimental result is explored, in order to explain experimentally observed phenomena in materials science problems. A series of published works in this theory-experiment combinatory approach will be introduced. The topics include the phase stability of Sb2O4, surface instability of MgB2, the interplay of diffusion and mechanical strengthening effect in multilayer, and latest findings of the syntheses of metallic nano-foams. The theory-experiment combinatory approach has proven to be useful in various materials science problems. The phase transformation trajectory of the Sb2O4 polymorphs, the surface reconstruction pathways of …

Generation, Manipulation, And Detection Of Charged Droplets And Ions In The Open Air, Adam Lee Hollerbach

Open Access Dissertations

This dissertation describes the development of methodologies for characterizing the physical properties of electrosprayed droplets and ions as they exist in the open air. Two novel ways of generating electrospray plumes were developed using voltage induction. Also described is a novel way to measure the sizes of electrosprayed droplets smaller than the diffraction limit of light using super resolution fluorescence microscopy. Studies performed in parallel to the sizing experiments describe an unconventional way of using ablative ions generated by corona discharges to probe chemical reactions occurring inside the inlets of mass spectrometers. Also described is the ability to direct and …

Optimal Placement Of A Small Order In A Diffusive Limit Order Book, Hyoeun Lee

Open Access Dissertations

A Limit Order Book (LOB), a trading system used by most of the electronic financial trading exchanges across the world, collects all the buy and sell limit orders: orders that specify a desired price and quantity. Limit orders are executed by matching them to the market orders: orders to buy or sell certain quantities or shares at the best available prices out of the standing limit orders in the book. In an order-driven market using the LOB system, one of the stock trader’s major concerns is to clear his/her inventory, by using a combination of limit orders and market orders. …

Disciplinary Differences In A Community Of Inquiry, Jieun Lim

Open Access Dissertations

The Community of Inquiry framework has been used in numerous studies, with over 1800 citations to date (Google Scholar, January 2018). These studies mostly involve the study of a single discipline and rarely examine disciplinary differences as a potential factor in student outcomes. To address the research gap this study examined the differences in students’ social, cognitive, and teaching presence and the effects of those presences on the students’ learning outcomes according to their academic disciplines.

This study used an explanatory sequential mixed-method design in two phases. The data were collected from 25 undergraduate online courses at two large public …

Nested Planetary Geartrain Design For Vibration Reduction Using Augmented Direct Gear Design Methodology, Cong Liao

Open Access Dissertations

The Noise, Vibration and Harshness (NVH) of a vehicle is one of the decisive indices of vehicle performance in terms of objective measures and subjective quality. The compact co-axial planetary geartrain of the automatic transmission, with its advantages of high gear reduction, controllable power split, distributed torque on multiple gears, and the ability to shift under load, is an irreplaceable core component in a vehicle’s powertrain. It plays an important role in providing a smooth, stable, and quiet ride. However, due to the complexity of planetary gearsets and various operating points of engine-transmission power matching, the planetary geartrain is also …

Enthusiastic Educators And Interested Visitors: Investigating The Relationships Between Museum Educators' Enthusiasm And Visitors' Situational Interest, Changchia James Liu

Open Access Dissertations

Informal education environments like museums have become some of the most important educational resources. Although much attention has been paid to museum settings and programs, little is known about how museum educators support visitors’ learning and intrinsic motivation. In particular, there is a need to investigate museum educators’ enthusiasm, considering that enthusiasm is a powerful way of creating an engaging learning experience across various subjects and environments. In this study, I investigate museum educators’ enthusiasm as perceived by adult visitors through the lens of interest development. The results I found (N = 209) indicate a strong positive relationship between museum …

Biologically Inspired Delay-Doppler Neighborhood Processing Of Radar Waveforms For Enhanced Delay-Doppler Resolution, I-Fan Liu

Open Access Dissertations

The delay-Doppler resolution of a radar system determines its ability to separate targets that are spatially close together and have similar radial velocities with respect to the radar. For this reason, the design of radar signals and signal processing with good delay-Doppler resolution has long been an ongoing active area of research. Radar systems typically use matched-filters to maximize the received signal-to-noise ratio and maximize target detection performance, in which case the delay-Doppler resolution of the radar waveform is given by the ambiguity function of the transmitted waveform.

Neurobiologists studying echolocation in bats have noted their outstanding resolution capabilities of …

Computationally Efficient Nonparametric Testing, Meimei Liu

Open Access Dissertations

A common challenge in nonparametric inference is its high computational complexity when data volume is large. In this thesis, I will introduce novel computationally efficient nonparametric testing methods. Firstly, we develop a computationally efficient nonparametric testing by employing a random projection strategy. In the specific kernel ridge regression setup, a simple distance-based test statistic is proposed. Notably, we derive the minimum number of random projections that is sufficient for achieving testing optimality in terms of the minimax rate. An adaptive testing procedure is further established without prior knowledge of regularity. One technical contribution is to establish upper bounds for a …

Evaluating The Efficacy Of Correlation-Based Meta-Analytic Structural Equation Modeling Under Different Patterns Of Missing Correlations, Jing Lv

Open Access Dissertations

Missing correlations often happen in the primary correlation matrices and create major problems for the performance of meta-analytic structural equation modeling (MASEM). In current literature, methodological investigation regarding the performance of MASEM methods paired with a large proportion of missing data is limited. This simulation study was designed to investigate the impacts of missing conditions on the correlation-based MASEM performance, utilizing weighted-covariance generalized least squares (W-COV GLS) with pairwise deletion (PD), W-COV GLS with multiple imputation (MI), and two-stage structural equation modeling (TSSEM) to pool the correlation matrices. Specifically, impacts of the study number (k), the within study sample size …

Efficient Support Of Text And Time In Spatial Data Systems, Ahmed R. Mahmood

Open Access Dissertations

The widespread use of GPS-enabled devices, e.g., smart-phones and GPS navigators has resulted in the generation of massive amounts of spatial data. This has led to the development of spatial data systems that process and manage spatial data effciently. Temporal and textual data often coexist with spatial data. This dissertation targets the effcient processing of spatio-temporal and spatio-textual data. To effciently support spatio-temporal data with limited temporal data retention, a new disk-based data structure for indexing moving objects trajectories with limited temporal data retention is introduced. To optimize the processing of spatio-textual data, a new frequency-aware spatio-textual indexing structure is …

Three Essays On The Economics Of Specialized Agricultural Products: Equilibrium Contract Structure And Firm Boundary Under Uncertainty And Sunk Costs, Tanner Joseph Mccarty

Open Access Dissertations

This dissertation contains three essays exploring how contractual form endogenously responds to uncertainty and irreversibility within a market for specialized agricultural products. It additionally explores the impact that this resulting contractual form has on rent and return distribution along the vertical supply chain. I accomplish this using a novel framework that meshes complete contracting and real options analysis. The first essay explores how equilibrium contract structure between an incumbent buyer and a seller considering entry into production of a specialized agricultural product endogenously responds to uncertainty and irreversibility. Results suggest that contract structure is sensitive to both the level and …