Engineering Commons^™

Shear And Fracture Behavior Of High Performance Concretes, Mahdi Arezoumandi

Doctoral Dissertations

"Concrete is the most widely used man-made material in the world. Like other materials, it has been improved over time. Nowadays, with continued development of science and technology, a new generation of concretes is produced and is termed high performance concretes. A review of previously published work indicates that very few studies (in some cases none) have addressed the structural behavior of full-scale, high performance concrete elements. This study investigated the shear and fracture behavior of two types of high performance concrete - high-volume fly ash concrete (HVFAC) and self-consolidating concrete (SCC). The HVFAC incorporates up to 70% cement replacement …

Recycling Of Electronic Waste: Printed Wiring Boards, Alex Luyima

Doctoral Dissertations

"Pyrolysis and leaching are the dominant techniques applied in the recycling of waste printed wiring boards (PWBs). Waste PWB pyrolysis is a highly polluting technology and produces brominated pyrolysis oils in addition to hydrogen bromide (HBr) gas. Moreover, leaching as a treatment process of waste PWBs is not well investigated. In this work, the pyrolysis of waste PWBs has been studied with the aim of reducing the amount of brominated oils and HBr gas evolved. The effects of powder inorganic chemicals (CaO, CaCO₃, Fe₂O₃, Al₂O₃, Y-Zeolite, and ZSM-5) additions on the pyrolysis of waste PWBs has been studied through experiments …

Implementation Of Project Based Learning Technique To Enhance Engineering Education, Dinesh Kanigolla

Masters Theses

"This study investigated the impact of introducing a semester project into three engineering courses where practical application of theoretical knowledge is applicable. Three courses were examined in this work: an undergraduate course in quality, a graduate course in Lean, and a graduate course in Six Sigma. For this research, student teams were given hands-on-projects that included collaboration with local companies. Surveys were conducted to assess the impact of project based learning on students' knowledge. Student responses were recorded and analyzed to determine how students felt the use of the semester project affected the course and to identify the response patterns …

Protein Aggregation At Solid/Liquid Interfaces: A Monte Carlo Study With Explicit And Implicit Solvent Effects, Rehman Fazeem

Masters Theses

"Metropolis Monte Carlo (MC) simulations were performed with positively charged peptides in aqueous solution to study changes in peptide conformations at solid/liquid interface, and its effects on protein aggregation. Intermediate-resolution diblock model peptide, comprising of 10 units of ALA (non-polar) and LYS (polar) amino acid residues, was used for the simulations. In the first approach to modeling, solvent effects were considered explicitly. The explicit model was then used to study two peptide molecules, in helical structure, at solid/liquid interface. In order to increase the number of peptide molecules in the simulation box, with reduced computational cost, an implicit solvent model …

Spatial Variation Of Amd Related Co₂ Emissions On Reclaimed Mine Spoil, Moagabo Mathiba

Doctoral Dissertations

"Carbon dioxide (CO₂) from acid mine drainage (AMD)-carbonate neutralization reactions in reclaimed mine spoils, can intermittently invade homes and structures constructed on or adjacent to these spoils in hazardous and even lethal concentrations (>15%) and rendering them uninhabitable. This phenomenon is beginning to be recognized as an emerging environmental, safety and health threat with potential environmental and financial liability for mine operators, developers and owners.

Like in natural soils, soil temperature and moisture, and possibly elevation are likely to influence CO₂ emissions from reclaimed mine spoils. However, mine spoil soils are heterogeneous and have significant convective transport due to …

Source Reconstructions For Ic Radiated Emissions Based On Magnitude-Only Near-Field Scanning, Ji Zhang

Doctoral Dissertations

"In this dissertation, a source reconstruction method is proposed to model the emission behavior of an IC by using magnitude-only information during near-field scanning. The phase-retrieval is accomplished during the back-forth iterations between two scanning planes of different heights. The magnitudes of fields on two planes of different heights are recorded and used to constrain the amplitude of the calculated fields during iterations. Three essential transformations among dipoles and fields are continued at each iteration step, until the convergence condition is achieved. The proposed algorithm has been verified by using a set of dipole-array as the original emitting sources, and …

Effect Of Dense Heat Exchanging Internals On The Hydrodynamics Of Bubble Column Reactors Using Non-Invasive Measurement Techniques, Mohammed Khloofh Al Mesfer

Doctoral Dissertations

"Given their efficiency and capital cost reduction, bubble/slurry bubble column reactors are the reactors of choice for Fischer-Tropsch (FT) synthesis, offering clean alternative fuels and chemicals. FT synthesis is an exothermic process that requires many heat exchanging tubes in order to remove heat efficiently and maintain the desired temperature and isothermal operating condition. The impact of the heat exchanging tubes (internals) on the hydrodynamics is not fully understood. Reliably designing and scaling up bubble column reactors requires proper understanding of hydrodynamics, as well as heat and mass transfer parameters.

The main objective of this work is to advance the understanding …

Minimizing Formation Damage For Preformed Particle Gels Treatment In Mature Reservoirs, Mahmoud Omran Elsharafi

Doctoral Dissertations

"This research studied the effect of preformed particle gels (PPGs) on unswept, low-permeable zones/areas. The objective was to find methods that minimized the damage caused by PPGs on unswept, low-permeable zones/areas, thus improving PPG treatment efficiency. These results can help to identify of the best PPG types, particle sizes, and brine concentrations for specific reservoirs and treatments. This study used sandstone core samples with various degrees of permeability. Two types of particle gels, a strong Daqing gel (DQ) and a weak Liquiblock™ 40k gel (40K), were used, each with a different strength.

This research included two stages. Firstly, both a …

Bio-Inspired Design, Fabrication And Testing Of Bipolar Plates For Pem Fuel Cells, Nannan Guo

Doctoral Dissertations

"The flow field of a bipolar plate distributes reactants for polymer electrolyte membrane (PEM) fuel cells and removes the produced water from the fuel cells. It greatly influences the performance of fuel cells, especially the concentration losses. Two approaches were developed to improve flow field designs in this dissertation. One is inspired by the biological circulatory structures and called bio-inspired designs, which have great potential to transport reactant efficiently and hence improve fuel cell performance. Another way is using a network-based optimization model to optimize the conventional flow field configurations, i.e., pin-type, parallel and serpentine designs, to improve flow distributions …

Common Mode Current Estimation For Cable Bundle Inside A Vehicle, Dazhao Liu

Doctoral Dissertations

"In the Section 1, it introduces a methodology to simulate the currents and fields during an air discharge ESD into a product by combining a linear description of the behavior of the DUT with a non-linear arc resistance equation. The most commonly used test standard IEC 61000-4-2 requires using contact mode discharges to metallic surfaces and air discharge mode to non-conducting surfaces. This paper proposes a method that combines the linear ESD generator full wave model and the non-linear arc model to simulate currents and fields in air discharge mode. In Section 2, when simulating surface and thin wire structures, …

Interacting Stress Concentration Factors And Their Effect On Fatigue Of Metallic Aerostructures, David Warren Whitley

Doctoral Dissertations

"During fabrication of certain aerostructure components, a situation can arise where a hole is mislocated so that it interferes with a radius, chem-mill step, machined step, or some other similar detail. The interaction of stress concentration effects between a hole and step are not well understood and the resulting impact on fatigue performance is difficult to predict. There exists a need for fatigue data that can be used to determine the analysis methods for evaluation of the interaction of machined steps and fastener holes. In this dissertation, the effect of stress concentrations placed in close proximity to each other and …

Model Based Fault Diagnosis And Prognosis Of Nonlinear Systems, Hasan Ferdowsi

Doctoral Dissertations

"Rapid technological advances have led to more and more complex industrial systems with significantly higher risk of failures. Therefore, in this dissertation, a model-based fault diagnosis and prognosis framework has been developed for fast and reliable detection of faults and prediction of failures in nonlinear systems. In the first paper, a unified model-based fault diagnosis scheme capable of detecting both additive system faults and multiplicative actuator faults, as well as approximating the fault dynamics, performing fault type determination and time-to-failure determination, is designed. Stability of the observer and online approximator is guaranteed via an adaptive update law. Since outliers can …

Numerical Analyses Of Long Carbon Fiber Reinforced Concrete Panels Exposed To Dynamic Loading, Zahra Sadat Tabatabaei

Doctoral Dissertations

"The purpose of this research was to evaluate impact and blast performance of long carbon fiber reinforced concrete experimentally and numerically. Experimental tests were conducted on plain concrete (PC), reinforced concrete, and four different types of long carbon fiber reinforced concrete (LCFRC). The results from each test were then compared to one another. This comparison indicates that adding long carbon fibers to concrete both increases the post-cracking behavior of concrete and decreases the spalls in either an impact or blast test. Among all of the fibers tested, Fiber Type B3 outperformed the other fibers, absorbing more energy during impact. Numerical …

Regional Geomorphic Analysis And Gis Susceptibility Mapping Of Landslides In The Blue Nile And The Tekeze River Basins Of Ethiopia, Elamin Hassan Dai Ismail

Doctoral Dissertations

"The Plateau region of Ethiopia lies within a seismically active continental extensional regime, which is being rapidly incised by the Blue Nile and the Tekeze Rivers. Extremely large landslides pose serious hazards in this highly populated region (>27 million), which is in the process of developing its hydrologic resources. This research sought to develop cost-effective methods to compile regional landslide inventory and landslide susceptibility maps, using geomorphic tools and GIS technologies. This work also sought to evaluate the relationships between landslide dams and knickpoints, caused by channel bed incision from those caused by slope failures, by utilizing identified knickpoints …

Synthetic Aperture Radar-Based Techniques And Reconfigurable Antenna Design For Microwave Imaging Of Layered Structures, Mojtaba Fallahpour

Doctoral Dissertations

"In the past several decades, a number of microwave imaging techniques have been developed for detecting embedded objects (targets) in a homogeneous media. New applications such as nondestructive testing of layered composite structures, through-wall and medical imaging require more advanced imaging systems and image reconstruction algorithms (post-processing) suitable for imaging inhomogeneous (i.e., layered) media. Currently-available imaging algorithms are not always robust, easy to implement, and fast. Synthetic aperture radar (SAR) techniques are some of the more prominent approaches for image reconstruction when considering low loss and homogeneous media. To address limitations of SAR imaging, when interested in imaging an embedded …