Engineering Commons^™

The Effects Of Personal Protective Respirators On Human Motor, Visual, And Cognitive Skills, Anas Ahmed Alghamri

Doctoral Dissertations

"In oxygen-deficient or toxic environments in which controlling the hazard is not feasible, workers wear personal protective respirators. Hazard controls include but are not limited to engineering controls, such as ventilation, and substituting less hazardous materials. However, respirator selection and the design of tasks that require respirators are critical issues. Understanding the effects of respirators on human abilities is critical to respirator selection and therefore to the safety and efficiency of workers. This research investigated the effect of respirators on human abilities. A review of the relevant literature was conducted, revealing that respirators can affect physiological, psychological, motor, and visual …

The Effect Of Supercritical Water On Crude Glycerin Solution, Jared Bouquet

Doctoral Dissertations

"Crude glycerin solution, a principal byproduct of the conventional biodiesel process, was reacted in supercritical water using a specially designed Haynesʼ Alloy 282 reactor system for the production of hydrogen rich syngas. The effects of temperature, pressure, water-to-carbon molar ratio, reactor residence time, and glycerin-to-methanol weight ratio on the extent of carbon gasification and gas composition were explored. Based on the results, the extent and selectivity of reactions that concurrently occur when methanol and glycerin are in the presence of supercritical water were analyzed. A decomposition reaction pathway for glycerin conversion to syngas was hypothesized, and then utilizing the results …

Shear And Fracture Behavior Of High-Volume Fly Ash Reinforced Concrete For Sustainable Construction, Carlos Andres Ortega Ordonez

Doctoral Dissertations

"Concrete is the most widely used man-made material on the planet. Unfortunately, producing Portland cement generates carbon dioxide (a greenhouse gas) at roughly a pound for pound ratio. High-volume fly ash (HVFA) concrete- concrete with at least 50% of the cement replaced with fly ash - offers a potential "green" solution. However, because it is still relatively new and has some disadvantages, there are still many questions that need to be answered. Most research to date has consisted only of the evaluation of the strength and durability of HVFA concrete mixtures, while only a limited number of studies have implemented …

Hollow Hydroxyapatite Microspheres As Devices For Controlled Delivery Of Proteins And As Scaffolds For Tissue Engineering, Hailuo Fu

Doctoral Dissertations

"Hollow HA microspheres were prepared by converting Li₂O-CaO-B₂O₃ glass microspheres in a K₂HPO₄ solution. Process parameters, such as reaction temperature (25°C-60°C) and concentration of the phosphate solution (0.02-0.25 M) significantly influenced the microstructure of the hollow HA microspheres. Microspheres with the largest hollow core size were obtained at lower temperature or with low K₂HPO₄ concentration. In comparison, microspheres with high surface area (~140 m²/g) were obtained at higher K₂HPO₄ concentration (0.25 M). Upon heat treatment (up to 900°C), the surface area of the hollow HA microspheres decreased (from ~100 m²/g to ~2 m²/g), and the rupture strength increased (from ~11 …

Manufacturing And Characterization Of Soy-Based Polyurethane Composites, Rama Bhadra Raju Vuppalapati

Doctoral Dissertations

"The major cost drivers for composites are raw materials and manufacturing process. Automated manufacturing processes like pultrusion and low cost bio-based raw materials can significantly lower the cost of composites. Polyurethane (PU) resin systems are being introduced in the pultrusion industry as they have higher performance characteristics and manufacturing feasibility when compared to conventional resin systems such as polyester and vinyl ester. PU resin systems are generally characterized as aromatic and aliphatic. Aliphatic PU has lower mechanical properties than the aromatic resin system due to its chemical structure. Nano materials can be used to increase the mechanical properties of aliphatic …

Numerical Simulations Of Fracture Propagation And Sealing: Implications For Wellbore Strengthening, Saeed Salehi

Doctoral Dissertations

"To mitigate the small tolerance between pore pressure and fracture gradients an engineering practice referred to as "wellbore strengthening" is conducted to increase the fracture gradient. The method relies on propping and/or sealing the fractures with specially designed materials. Different competing theories exist for physical wellbore strengthening mechanisms which can be categorized into two groups. The first group explains that strengthening happens as a result of increasing wellbore hoop stress when fractures are sealed while the second group emphasis is on fracture tip isolation with suitable materials and enhancing fracture propagation pressure. The numerical models and lab experiments …

Real-Time Localization Using Received Signal Strength, Mohammed Rana Basheer

Doctoral Dissertations

"Locating and tracking assets in an indoor environment is a fundamental requirement for several applications which include for instance network enabled manufacturing. However, translating time of flight-based GPS technique for indoor solutions has proven very costly and inaccurate primarily due to the need for high resolution clocks and the non-availability of reliable line of sight condition between the transmitter and receiver. In this dissertation, localization and tracking of wireless devices using radio signal strength (RSS) measurements in an indoor environment is undertaken. This dissertation is presented in the form of five papers.

The first two papers deal with localization and …

Modeling Aperture Radiation For Rf Interference Applications, Liehui Ren

Doctoral Dissertations

"The first topic proposes a rigorous method of moments(MoM) solution to evaluate the shielding effectiveness of a metallic enclosure with apertures on top wall by formulating a pair of coupled mixed potential integral equations (MPIEs). Application of Ewald transform to the computation of Green's function in the cavity yields fast convergence of series summation. Good agreements with a commercial tool, EMC studio, have proved the effectiveness of the proposed approach.

The second topic deals with prediction of electromagnetic interference radiation from components or interconnects in a printed circuit board by using convolution of the half-space Green's functions and the equivalent …

Characterization Of Soil Variability For Reliability-Based Design, Sitenikechukwu Onyejekwe

Doctoral Dissertations

"A very carefully planned Missouri-wide field exploration and laboratory investigation program, with a focus on fine-grained soils, was executed with the aim of characterizing the variability of geotechnical parameters statistically with a view to increasing the use of reliability-based design (RBD) among geotechnical engineers. Geotechnical parameters were characterized in terms of both their first and second statistical moments and their coefficient of variation (COV). Their probability distributions and their scale of fluctuation, θ, were also determined. Correlations between difficult-to-obtain parameters and more easily-obtained parameters were developed and the degree of fit of study data to published empirical correlations was investigated. …

Densification And Thermal Properties Of Zirconium Diboride Based Ceramics, Matthew Joseph Thompson

Doctoral Dissertations

"The research presented in this dissertation focuses on the processing and thermomechanical properties of ZrB₂ based ceramics. The overall goal was to improve the understanding of thermal and mechanical properties based on processing conditions and additives to ZrB₂. To achieve this, the relationships between the thermal and mechanical properties were analyzed for ZrB₂ ceramics that were densified by different methods, varying amounts of carbon, B₄C, or TiB₂ additions. Four main areas were investigated in this dissertation. The first showed that decreased processing times, regardless of densification method, improved mechanical strength to >500 MPa. This study also revealed that lower oxygen …

Free-Radical Maleation Of Poly(Butylene Adipate-Co-Terephthalate) In Supercritical Carbon Dioxide And Its Effect On The Percolation And Deformation Mechanism Of Layered Silicate Nanocomposites, Alexandria Niemoeller

Doctoral Dissertations

The utilization of compostable polymers such as poly(butylene adipate-co-terephthalate) (PBAT) in single-use packaging applications can mitigate the water, solvents, and energy required for processing plastic waste. PBAT exhibits exceptional elongational properties, but its moderate water vapor permeability and low tensile modulus limit the applications in which PBAT can be employed. In this work, PBAT nanocomposites were produced at various loadings of organically-modified montmorillonite. The secondary structure of nanoparticles formed within the PBAT matrix was evident in the terminal region of the linear viscoelastic response under oscillatory shear, and a percolation threshold was determined to occur at 3.88% clay by weight. …

Glycerin Reformation In High Temperature And Pressure Water, Jason W. Picou

Doctoral Dissertations

"The noncatalytic reformation of glycerin in supercritical water was studied in a Haynes 282 tubular reactor. In order to determine which parameters were the most influential, a 2³ experimental matrix was conducted, with temperatures of 500 and 700⁰C, water/glycerin molar ratios of 3:1 and 13:1, and residence times of 30 and 90 seconds, all at a pressure of 24 MPa. It was found that temperature had the largest effect on the two gasification parameters deemed most important, gasification percentage and hydrogen yield. Based on this, the effect of temperature was further investigated by looking at 5⁰C intervals from 500 to …

The Risk Mitigation Strategy Taxonomy And Generated Risk Event Effect Neutralization Method, Daniel A. Krus

Doctoral Dissertations

"In the design of new products and systems, the mitigation of potential failures is very important. The sooner in a product's design mitigation can be performed, the lower the cost and easier to implement those mitigations become. However, currently, most mitigations strategies rely on the expertise of the engineers designing a product, and while models and for failure modes do exist to help, there are no guidelines for performing product changes to reduce risk. To help alleviate this, the risk mitigation strategy taxonomy is created from an empirical collection of mitigation strategies used in industry for failure mitigation, creating a …

Dynamic Decision Making Under Uncertainty In Renewable Energy Portfolio Management And Inventory Management, Jianjun Deng

Doctoral Dissertations

"It is challenging and important for a firm to make effective decisions under uncertainties, such as random fluctuations of products prices or demands, etc. This dissertation formulates mathematic models to help decision makers in energy and retail industries make optimal timing and optimal operational decisions when facing uncertain electricity prices and demands. As for energy portfolio management, the optimal entry and dispatch strategies are investigated for an electricity generating firm to introduce a renewable power plant as an alternative method for generating electricity, with or without construction delay. In addition, the abandonment strategies of considering shutting down one of the …

Organoclay Dispersion In Linear Low-Density Polyethylene And Maleated Linear Low-Density Polyethylene Via Supercritical Carbon Dioxide Processing, Matthew J. Factor

Doctoral Dissertations

"Research into polymer-clay nanocomposites (PCN's) has been ongoing for decades as a result of the property enhancements offered by clay. To fully exploit these property enhancements, organically modified clays (organoclays) are utilized to promote clay delamination by reducing the disparity between the hydrophilicity of the clay and the hydrophobicity of the highly used polyolefin polymer. Since the organic modification of organoclays can degrade at temperatures typical to many polymers during melt-mix processing, this work utilizes the low-temperature processing fluid supercritical carbon dioxide (scCO₂) to disperse an organoclay into the highly used polymer LLDPE and ascertains the associated processing conditions for …

Performance Characterization And Optimization Of Microgrid-Based Energy Generation And Storage Technologies, Joe D. Guggenberger Ii

Doctoral Dissertations

"Renewable energy-powered microgrids have proven to be a valuable technology for self-contained (off-grid) energy systems. Characterizing microgrid system performance pre-deployment would allow the system to be appropriately sized to meet all required electrical loads at a given renewable source operational time frequency. A vanadium redox battery was empirically characterized to determine operating efficiency as a function of charging characteristics and parasitic load losses. A model was developed to iteratively determine system performance based on known weather conditions and load requirements. A case study was performed to compare modeled system performance to measurements taken during operation of the microgrid system. Another …

Updated Eor Screening Criteria And Modeling The Impacts Of Water Salinity Changes On Oil Recovery, Ahmad Aladasani

Doctoral Dissertations

"Developing technologies for enhanced oil recovery (EOR) from existing oil fields would supply the world's energy needs for several decades. The application of EOR in many major oil-producing countries remains in its conceptual stage. Thermal and gas EOR methods achieve high incremental rates; however, their application range has not broadened significantly as they have matured, while the rate at which new, promising EOR methods such as Low-salinity water flooding (LSWF) are being implemented is alarming. Despite, the potential of LSWF its development and application has been hindered by the lack of consensus concerning its recovery mechanism(s). Every oil reservoir has …

A Progressive Collapse Evaluation Of Steel Structures In High Temperature Environment With Optical Fiber Sensors, Ying Huang

Doctoral Dissertations

"In the process of a progressive failure of steel structures in a post-earthquake fire, real-time assessment and prediction of structural behaviors are of paramount significance to an emergency evacuation and rescue effort. However, existing measurement technologies cannot provide the needed critical data such as large strains at high temperature. To bridge this gap, a novel optical fiber sensor network and an adaptive multi-scale finite element model (FEM) are proposed and developed in this study. The sensor network consists of long period fiber gratings (LPFG) sensors and extrinsic Fabry-Perot interferometer (EFPI) sensors or their integration. Each sensor is designed with a …

Saturation Effects On Mechanical Excavatability Of Roubidoux Sandstone Under Selected Rock Cutting Tools, Muhammad Zubair Abu Bakar

Doctoral Dissertations

"This study investigated the differences in the cutting performance of two rock cutting tools in dry and saturated rock. For this purpose, a permeable quartzose sandstone was subjected to a series of full scale linear rock cutting tests, in both dry and saturated conditions, using a constant cross-section (CCS) disc cutter and a radial drag pick at a constant cutting speed.

In this rock, saturation with water reduced the forces acting on the disc cutter by 27-48% (significant at 90% confidence), but also reduced the chip yield by nearly as much. Even though the specific energy of fragmentation went down …

Modeling Multi-Layer Via Structure Using Peec Method, Hanfeng Wang

Doctoral Dissertations

"In this dissertation, a new integral equation formulation for via structures is developed for the capacitance extraction between vias and planes. The proposed method can be used to calculate the shared-antipad via structure which is widely used in highspeed differential signal interconnects. In addition, we use the image theory to handle inhomogeneous media. Further, a new technique is given to reduce computational resources for via-to-plane structures based on properties of the matrix coefficient. The extracted capacitance is also incorporated into the physics-based circuit model to characterize the overall performance of the via transition. In the second paper, a rigorous modeling …

Null Convention Logic Applications Of Asynchronous Design In Nanotechnology And Cryptographic Security, Jun Wu

Doctoral Dissertations

"This dissertation presents two Null Convention Logic (NCL) applications of asynchronous logic circuit design in nanotechnology and cryptographic security. The first application is the Asynchronous Nanowire Reconfigurable Crossbar Architecture (ANRCA); the second one is an asynchronous S-Box design for cryptographic system against Side-Channel Attacks (SCA). The following are the contributions of the first application: 1) Proposed a diode- and resistor-based ANRCA (DR-ANRCA). Three configurable logic block (CLB) structures were designed to efficiently reconfigure a given DR-PGMB as one of the 27 arbitrary NCL threshold gates. A hierarchical architecture was also proposed to implement the higher level logic that requires a …

Lyapunov Based Optimal Control Of A Class Of Nonlinear Systems, Hassan Zargarzadeh

Doctoral Dissertations

"Optimal control of nonlinear systems is in fact difficult since it requires the solution to the Hamilton-Jacobi-Bellman (HJB) equation which has no closed-form solution. In contrast to offline and/or online iterative schemes for optimal control, this dissertation in the form of five papers focuses on the design of iteration free, online optimal adaptive controllers for nonlinear discrete and continuous-time systems whose dynamics are completely or partially unknown even when the states not measurable. Thus, in Paper I, motivated by homogeneous charge compression ignition (HCCI) engine dynamics, a neural network-based infinite horizon robust optimal controller is introduced for uncertain nonaffine nonlinear …

A Socio-Technical Analysis Of Widespread Electric Vehicle Adoption, Onanwa Nneka Egbue

Doctoral Dissertations

A combination of high fuel costs, concerns about petroleum availability, and environmental issues associated with conventional vehicles powered by fossil fuels are driving interests in electric vehicles (EVs). Large-scale deployment of EVs can play a significant role in addressing some of these problems. In spite of the benefits of EVs, several obstacles need to be overcome before EVs will be widely adopted. This research focuses on two socio-technical issues that affect widespread adoption and sustainability of EVs, consumer attitudes and perceptions, and supply chain risks of raw materials for EV battery technology. A major barrier is that consumers tend to …

Purification Of Metals Through Filtration And Electromagnetic Separation, Lucas Nana Wiredu Damoah

Doctoral Dissertations

"The applicability of a high frequency electromagnetic field to the removal of nonmetallic inclusions from silicon and aluminum, and the mechanism of depth mode filtration during aluminum purification were investigated. Electromagnetic separation experiments at frequencies of 63 - 120 kHz and aluminum filtration experiments using both conventional Al₂O₃ filters and AlF₃ coated Al₂O₃ filters were carried out by flowing molten aluminum through, and partly solidified in the filter bed followed by analysis of the metal and filter material. Materials were characterized with an optical microscope and macroscope, scanning electron microscope (SEM/EDX), x-ray diffraction (XRD), electron probe microanalysis (EPMA) and glow …

Characterization Of Expanded Polystyrene (Eps) And Cohesive Soil Mixtures, Nicholas Thomas Rocco

Doctoral Dissertations

"Soils modified with expanded polystyrene (EPS) particulates could be used as lightweight fill in a variety of installations including slopes for improved stability, embankments over compressible soils, and to reduce earth pressures next to structures. The addition of low density EPS particulates into soil has a large effect on the mass and volumetric characteristics of these mixtures and their influence on mechanical properties is scarce in the literature. A laboratory characterization program using clay mixed with EPS particulates was conducted for different dosages of EPS. Soils were modified with up to 1.5% EPS by mass, which corresponds to approximately 45% …

An Improved Dipole-Moment Model Based On Near-Field Scanning For Characterizing Near-Field Coupling And Far-Field Radiation From An Ic, Zhenwei Yu

Doctoral Dissertations

"Radio Frequency Interference (RFI) problems are critical issues in wireless platform design. The accurate noise model of integrated circuits (ICs) is needed to help designers to diagnose and predict RFI problems. In this dissertation, an improved IC radiated emission model based on near-field measurements is proposed. The regularization technique and the truncated SVD method are employed together with the least square method to calculate the dipole moments from the near-field data. This dipole model has clear physical meaning: the electric and magnetic dipoles represent the voltage and the current in the circuit, respectively. One application of this dipole model is …

Thermal Properties Of Spinel Based Solid Solutions, Kelley R. Wilkerson

Doctoral Dissertations

"Solid solution formation in spinel based systems proved to be a viable approach to decreasing thermal conductivity. Samples with systematically varied additions of MgGa₂O₄ to MgAl₂O₄ were prepared and thermal diffusivity was measured using the laser ash technique. Additionally, heat capacity was measured using differential scanning calorimetry and modeled for the MgAl₂O₄-MgGa₂O₄ system. At 200⁰C thermal conductivity decreased 24% with a 5 mol% addition of MgGa₂O₄ to the system. The solid solution continued to decrease the thermal conductivity by 13% up to 1000⁰C with 5 mol% addition. The decrease in thermal conductivity ultimately resulted in a decrease in heat flux …

Addressing Control And Capacitor Voltage Regulation Challenges In Multilevel Power Electronic Converters, Hossein Sepahvand

Doctoral Dissertations

Multilevel power electronic converters are the current industry solutions for applications that demand medium voltage, reasonable efficiency, and high power quality. The proper operation of these types of power converters requires special control, modulation methods, and capacitor voltage regulation techniques. Both developing capacitor voltage regulation methods and addressing their associated issues with such fall within the primary focus of this dissertation. In this dissertation an investigation was conducted on the capacitor voltage regulation constraints in cascaded H-bridge multilevel converters with a staircase output voltage waveform. In the proposed method, the harmonic elimination technique is used to determine the switching angles. …

A Comparison Analysis Of Defensive Routines And Theories-In-Use Of Engineering And Non-Engineering Managers, Tyria Riley

Doctoral Dissertations

"Engineering managers are managers who have an understanding of both the technical and business world in organizations. Many lead teams of their peers who are purely technical individuals. However, the success of an engineering manager depends on being able to function in both worlds when necessary. There is a stigma that engineers experience challenges in areas such as communication, conflict resolution, and leadership. Due to these challenges, defensive routines are likely to exist. Defensive routines are behaviors that are common in many managers and may hinder the success of an organization. This research uses a case study approach to measure …

A Methodology For Statistical Propped Fracture Treatment Design In Fluvial Environments, Prue Elizabeth Smith

Doctoral Dissertations

"Treatment design for hydraulic fracturing historically has been deterministic in nature. In a deterministic design, required variables can be determined and are assumed to be laterally continuous. This is difficult for geologic settings in general, but nearly impossible in fluvial geologic environments where the second assumption is violated.

Recent work has employed statistical methods to account for the complexity and heterogeneity in fluvial environments. Statistical design tools have been used to assist with improving the design process in complex fluvial geologic systems. Currently, the statistical design tools must be created using a "trial and error" process, which requires first completing/fracturing …