Digital Commons Network^™

Two-Point Bend Studies Of Glass Fibers, Zhongzhi Tang

Doctoral Dissertations

"The principal objective of this research is to advance our understanding of how glass breaks. Glass, a material well known for its brittleness, has been used widely but within a frustrating limit of its strength. Generally, strength is not considered as an intrinsic property of glass, due to the difficulty of avoiding the presence of flaws on the sample surface. The fiber drawing system and two-point bending (TPB) equipment developed at Missouri S&T allow the fabrication of pristine glass fibers and failure strain measurements while minimizing the effects of strength limiting critical flaws. Several conditions affect the failure behavior of …

Ozone And Terpene Reactions On Indoor Surfaces: Reaction Rates And Implications For Indoor Air Quality, Shi Shu

Doctoral Dissertations

No abstract provided.

Alloy Dissolution In Argon Stirred Steel, Darryl S. Webber

Doctoral Dissertations

"Alloying is required for the production of all steel products from small castings to large beams. Addition of large quantities of bulk alloys can result in alloy segregation and inconsistent alloy recovery. The objective of this research was to better understand alloy dissolution in liquid steel especially as it relates to Missouri S&Ts' patented continuous steelmaking process. A 45-kilogram capacity ladle with a single porous plug was used to evaluate the effect of four experimental factors on alloy dissolution: alloy species, alloy size or form, argon flow rate, and furnace tap temperature. Four alloys were tested experimentally including Class I …

Diesel Particulate Matter Dispersion Analysis In Underground Metal/Nonmetal Mines Using Computational Fluid Dynamics, Yi Zheng

Doctoral Dissertations

"Diesel Particulate Matter (DPM) is a natural by-product from operating diesel engines. Since diesel power is a major source of energy for mining operations today, the adverse health effects of DPM are of a great concern. To thoroughly resolve DPM problems, it is critical that DPM propagation characteristics be understood to arrive at a sensible and practical method for addressing DPM-related issues. To achieve this, a computational fluid dynamics (CFD) method is used to simulate DPM dispersion and to predict its concentration distribution. Industrial field studies were reconstructed to evaluate the possibility of different CFD models. Experiments were also carried …

Postcyclic Behavior Of Low-Plasticity Silt, Shuying Wang

Doctoral Dissertations

"Liquefaction of low-plasticity silt has been reported during earthquakes in the recent past. Excess pore pressure builds up due to the dynamic loading and then dissipates. The postcyclic behavior of low-plasticity silt was investigated in this research for materials obtained from the Mississippi River Valley. The experimental program involved specimen preparation using a slurry consolidation approach. A special technique was developed for specimen movement, reducing the testing program time by half. Both static and cyclic triaxial tests were conducted to confirm the ability to prepare replica specimens. In order to characterize the monotonic behavior, triaxial tests were conducted to determine …

Dynamic Ergonomic Analysis And Simulation Of Fastening Operation, Akul Joshi

Doctoral Dissertations

"Operator performing fastening operation with powered hand-tools at awkward postures is subjected to external forces that may pose a risk of developing ergonomic injuries. For design of safe workplaces and selection of tools it is necessary to identify the probable causes of discomfort by simulating the work conditions and quantifying the risk factors. An ergonomic simulator is developed to simulate the fastening operation and quantify the effects of posture and force in fastening operation. The effect of dynamic forces is analyzed using two approaches. The first approach analyzes the effect of tool vibration while the second analyzes the hand-arm system …

Leaching Characteristics Of Inorganic Contaminants From Coal Fly Ash, Tingzhi Su

Doctoral Dissertations

"Leaching of trace elements raises environmental concerns in coal fly ash disposal and reuse. US EPA is in the process of creating the first national rule on coal ash management. However, due to the complexity of coal fly ash composition, the leaching characteristics of trace elements are not well understood. Meanwhile, driven by the tightening emission regulations, new types of coal fly ashes are continuously generated as a result of the technological evolution at coal energy industry. The changing landscape highlights the needs for a comprehensive database to assess the leaching characteristics of different types of coal fly ashes, evaluation …

Preliminary Model Development Of Metal Complexation Of Polyester Derivatives Of 2,2'-Biimidazole, Shelonda Rena Taylor Finch

Doctoral Dissertations

"The objective of this study was to develop a chemical model for metal ion complex formation by a macroligand system with multi-metal binding sites using 2,2'-biimidazole as the starting molecule of the ligand system. Prior studies in this laboratory guided the selection of diesters and hydroxyethyl derivatives of 2,2'-biimidazole as model monomers. In addition, metal ion complexation studies with 2,2'-biimidazole derivatives were conducted. As a result, crystal structures of 1,1'-di(methylpropionato)-2,2-biimidazole, 2,2'-bis(1H-imidazolium) dinitrate and silver 2,2'-bis(1H-imidazolium) trinitrate, were reported. The crystal structures indicated a dependence upon the binding ability of the protonated 2,2'-biimidazole and counter ions. transesterification of the diesters and …

Processing And Characterization Of Boron Carbide-Hafnium Diboride Ceramics, Harlan J. Brown-Shaklee

Doctoral Dissertations

"Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB₂ sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB₂ powder in part by removing oxides at the HfB₂ surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB₂ by 150⁰C compared to carbon, which reduced the hot pressing temperature by ~50⁰C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, …

Workforce Planning Models For Semiconductor Manufacturing: Assembly-Test Operations, Shrikant Jarugumilli

Doctoral Dissertations

"We present a framework that integrates strategic and operational workforce planning models. Since these models provide decisions for planning horizons with different lengths, the formulation and solution strategy should ensure that the flow of information between these models is both appropriate and consistent.

The single-shift workforce planning problem is formulated as a two-phase goal program. In the first phase, the model allocates the workers to machine groups and identifies the shortage of workers (referred to as gap) followed by the second phase, in which certain constraints are relaxed and the workers are reallocated to the machine groups in order to …

Enhanced Heavy Oil Recovery By Alkali-Surfactant In The Pennsylvania Warner Sandstone, Rabia Mohamed Hunky

Doctoral Dissertations

"In this research, a study of the non-thermal method of alkaline-surfactant (AS) flooding to enhance heavy oil recovery from the Pennsylvanian Warner sandstone reservoir in Western Missouri was conducted. This work includ [sic] testing approximately 30 commercial surfactants and using a heavy oil sample with an API of 17. It was found that a number of surfactants could create stable emulsions. The viscosity of heavy oil could be reduced from 18,518 cp to 2.5 cp at 25⁰C through emulsification of certain surfactants. One of the major findings was that the emulsion created by the commercial surfactant, Igepalʼ CO-530 was stable …

Apparent Weekly And Daily Earthquake Periodicities In The Western United States, And Evolution Of Wadi Kubbania In Egypt, Ali Hadi Atef

Doctoral Dissertations

"The dissertation consists of two separate sections. The first section is on apparent daily and weekly periodicities in earthquake occurrence in the western United State [sic]. Analysis of Apparent Seismicity Rate (ASR) in the western United States confirmed the existence of prominent spectral peaks with a period of 1 and 7 days. The number of recorded earthquakes on Sundays for the duration of 1963-2008 is about 5% higher than that on weekdays, and, more significantly, there is a 9% increase of ASR in the early morning compared with that in the middle of the days. Significant similarities between the spatial …

Development Of A Simple Vibration Model For Predicting The Structural Dynamics Of An Hcci Engine, Jeffery A. Massey

Doctoral Dissertations

"The hypothesis tested in this work is that the surface vibration and radiated sound of an engine operating under HCCI combustion is dominated by the free vibration response of the engine's structural components to an impulsive loading brought about by the rapid energy release of the HCCI combustion process. Recent work by the author has shown that classical vibration theory describing the dynamic response of a single-degree-of-freedom (SDOF) oscillator may capture the major characteristics of the engine surface vibrations. Through an experimental investigation of HCCI combustion engine dynamics this model has been developed further.

A band level analysis of measured …

Re-Imagining Individual And Communal Identity : Corporate Mergers, Susan Duvall-Dickson

Doctoral Dissertations

unavailable

An Exploration Of The Experiences Of Flow By Skilled Professional Contract Workers, Patricia C. Johnson

Doctoral Dissertations

unavailable

The Effects Of Three Concept Mapping Strategies On Seventh-Grade Students' Science Achievement At An Urban Middle School, Navdeep Dosanjh

Doctoral Dissertations

unavailable

Spiking Neural Networks And Their Applications, Cameron Eric Johnson

Doctoral Dissertations

"Artificial neural networks (ANNs) have been developed as adaptable, robust function approximators for at least the last quarter-century. They have progressed through two generations, and the third is now under development. Spiking neural networks (SNNs) seek to improve on previous generations in two ways: by using a more biologically-inspired neuron, they are shown to be capable of more complex calculations; incorporating polychronous properties of highly-recurrent networks with delays of different lengths on each synapse to achieve large numbers of possible patterns with relatively few neurons and synapses.

Abstracted spiking neurons have been used as a third-generation activation function in a …

Additivity Of Strengthening Mechanisms In Ultrafine Grained Aluminum Alloy, Nilesh Kumar

Doctoral Dissertations

"Friction stir processing (FSP) has been used in the present work to obtain ultrafine grained (UFG) microstructure in a twin-roll cast (TRC) Al-Mg-Sc alloy. An attempt has been made to establish a correlation between processing, microstructure, and properties (mechanical) in UFG regime for this alloy system.

The effect of initial microstructural conditions and processing parameters (tool rotation rate) were shown to have a profound impact on the development of UFG microstructure. FSP led to a microstructure consisting of grains with an average grain size as small as 390 nm, having high angle grain boundaries and a completely random texture. The …

One Pot Synthesis Of Metal, Carbides And Polymeric Aerogels, Naveen K. Chandrasekaran

Doctoral Dissertations

"Ultra-low density, three-dimensional assemblies of nanoparticles are referred to as aerogels, and typically are derived from supercritical fluid (SCF) drying of wet-gels. Aerogels are generally fragile materials, but that issue has been addressed successfully by X-aerogels, in which the inorganic nanoparticle framework plays the role of the template for the accumulation of polymer that connects covalently and crosslinks the nanoparticles. The resulting materials can be 300x stronger than the native network, for a nominal increase in density by a factor of 3x. Since the exceptional mechanical properties of X-aerogels are traced to the conformal polymer coating, it was reasonable to …

Two New Spline-Based Methods And Real Data Applications: High-Resolution Receiver Function Calculations From Teleseismic Broadband Waveforms And High-Accuracy Practical Potential-Field Integral Transformations, Bingzhu Wang

Doctoral Dissertations

"While receiver function (RF) calculation is fundamentally important and widely used, it is not well solved due to unstable deconvolution. A spline-based RF calculation method was proposed and it is demonstrated that both individual RFs and the stacked RF calculated with the spline method have sharper peaks than those with the water-level spectral division method and the iterative deconvolution method. At the common peaks on the stacked RFs, there are close similarities for all three RF calculation methods. The better calculated RFs with the spline method lead to improved H - K analysis and improved determination of the optimal Moho …

Agent-Based Analysis And Mitigation Of Failure For Cyber-Physical Systems, Jing Lin

Doctoral Dissertations

"Techniques exist for assessment, modeling, and simulation of physical and cyber infrastructures, respectively; but such isolated analysis is incapable of fully capturing the interdependencies that occur when they intertwine to create a cyber-physical system (CPS). The first contribution of this doctoral research includes qualitative representation of the operation of a CPS in a single multi-agent model. Dependable operation of a CPS is contingent upon correct interpretation of data describing the state of the system. To this end, we propose agent-based semantic interpretation services that extract useful information from raw sensor data. We utilize the summary schemas model to reconcile differences …

Impact Of Stochastic Loads And Generations On Power System Transient Stability, Theresa Odun-Ayo

Doctoral Dissertations

"Randomness in physical systems is usually ultimately attributed to external noise. Dynamic systems are driven not only by our own control inputs, but also disturbances which cannot be modeled deterministically. A linear system model is justifiable for a number of reasons, often such a model is adequate for the purpose at hand, and when non-linearities do exist, the typical engineering approach is to linearize about some nominal point or trajectory to achieve a perturbation or error model. However, in order for the resulting model to fit data generated by the real world, these disturbances need to be modeled stochastically. The …

Hardware Emulation Of Wireless Communication Fading Channels, Fei Ren

Doctoral Dissertations

"This dissertation investigates several main challenges to implementing hardware-based wireless fading channel emulators with emphasis on incorporating accurate correlation properties. Multiple-input multiple-output (MIMO) fading channels are usually triply-selective with three types of correlation: temporal correlation, inter-tap correlation, and spatial correlation. The proposed emulators implement the triply-selective fading Channel Impulse Response (CIR) by incorporating the three types of correlation into multiple uncorrelated frequency-flat Rayleigh fading waveforms while meeting real-time requirements for high data-rate, large-sized MIMO, and/or long CIR channels. Specifically, mixed parallel-serial computational structures are implemented for Kronecker products of the correlation matrices, which makes the best tradeoff between computational speed …

Architecture Value Mapping: Using Fuzzy Cognitive Maps As A Reasoning Mechanism For Multi-Criteria Conceptual Design Evaluation, Atmika Singh

Doctoral Dissertations

"The conceptual design phase is the most critical phase in the systems engineering life cycle. The design concept chosen during this phase determines the structure and behavior of the system, and consequently, its ability to fulfill its intended function. A good conceptual design is the first step in the development of a successful artifact. However, decision-making during conceptual design is inherently challenging and often unreliable. The conceptual design phase is marked by an ambiguous and imprecise set of requirements, and ill-defined system boundaries. A lack of usable data for design evaluation makes the problem worse. In order to assess a …

Robust Adaptive Filtering Algorithms For System Identification And Array Signal Processing In Non-Gaussian Environment, Tiange Shao

Doctoral Dissertations

"This dissertation proposes four new algorithms based on fractionally lower order statistics for adaptive filtering in a non-Gaussian interference environment. One is the affine projection sign algorithm (APSA) based on L₁ norm minimization, which combines the ability of decorrelating colored input and suppressing divergence when an outlier occurs. The second one is the variable-step-size normalized sign algorithm (VSS-NSA), which adjusts its step size automatically by matching the L₁ norm of the a posteriori error to that of noise. The third one adopts the same variable-step-size scheme but extends L₁ minimization to Lp minimization and the variable step-size normalized fractionally lower-order …

Surface Modification Of Micro-Fluidic Devices, Zhan Gao

Doctoral Dissertations

"The surface modification, fabrication and characterization of microfluidic sensor systems for oxygen and glucose measurements with the use of polymeric materials were investigated in this dissertation. This dissertation is prepared in publication format. The first manuscript focuses on the surface modification of SU -8 layer to enhance the wettability. The improvement of wettability is critical since biofouling can be minimized during bioanalysis. A novel in situ photopattemable grafting technology was used to attach biocompatible polymer layers on SU-8 surface, changing its property from hydrophobicity to hydrophilicity. The results were confirmed by contact angle measurement and Fourier Transform Infrared (FTIR) spectra. …

Sandwich Structures With Advanced Facings, Cody H. Nguyen

Doctoral Dissertations

"The purpose of this research is to investigate potential advantages of two innovative designs of sandwich panels. The first design involves sandwich panels with a piece-wise thickness of the facings aiming at two possible outcomes: (I) improved the structural response, i.e. strength and stiffness, without increasing the weight of the structure or (2) reduction in the weight of the structure without a detriment to its structural response. The analysis is conducted analytically using the first-order shear deformation theory and numerically by the finite element analysis of conventional and stepped-wise sandwich panels. The applicability of the first-order shear deformation theory to …

Being And Becoming Public School Teachers: Career Mobility Of Chinese Overseas-Trained Teachers In The San Francisco Bay Area, Lily L. Chow

Doctoral Dissertations

Teacher shortage and retention has persisted in the United States for decades. Ethnic minority teachers are underrepresented in public K-12 schools as well as teachers for English learners. Untapped pools of overseas-trained teachers who are lawful permanent residents exist but are unemployed, underemployed, or working in other fields. To earn a local teaching credential, the immigrant bears the burden of proving equivalent knowledge and skills to re-enter her or his profession in the United States. At the time of this study, there was no research about overseas-trained immigrant teachers entering the teaching profession for primary and secondary public school students …

Transcending Borders: The Experience Of Six Undocumented Immigrant Mothers In The United States, Patricia Derobles

Doctoral Dissertations

The purpose of this study was to gain meaningful insights into the experiences of six undocumented immigrant mothers as they settled in the United States while they raise and participate in the educational life of their children. Currently 10 % of California's 6 million students originate from homes where one or two parents are undocumented, poor and have limited English skills. Undocumented immigrants live in constant fear of deportation, live and work in the shadows of mainstream society, are stigmatized by the media, are criminalized by immigration law and exploited by their employers. Historically, children originating from immigrant homes have …

Grading And Reporting Purposes And Practices In Catholic Secondary Schools And Grades' Efficacy In Accurately Communicating Student Learning, Peter Imperial

Doctoral Dissertations

Few aspects of school are as controversial as the practice of grading, for grades affect students' educational opportunities. The purpose of this study was to identify the practices Catholic high-school teachers employed in determining students' grades. The study investigated the extent to which academic achievement comprised the grades teachers reported, and the extent to which teachers' practices are consistent with their expressed purposes for grading. The study also explored the extent to which Catholic teachers' grading practices are consistent with their schools' purpose for grading. Using random sampling, 486 Catholic secondary school teachers and 50 administrators from 33 high schools …