Engineering Commons^™

Effect Of Microstructure And Alloying Elements On The Resistance Of Fastener Grade Steels To Hydrogen Assisted Cracking , Nicholas E. Nanninga

Dissertations, Master's Theses and Master's Reports - Open

Fastener grade steels with varying alloy contents and heat treatments were employed to measure changes in resistance to hydrogen assisted cracking. The testing procedure compared notched tension specimens fractured in air to threshold stress values obtained during hydrogen charging, utilizing a rising step load procedure. Bainitic structures improved resistance by 10-20% compared to tempered martensite structures. Dual phase steels with a tempered martensite matrix and 20% ferrite were more susceptible and notch sensitive. High strength, fully pearlitic structures showed an improvement in resistance. Carbon content, per se, had no effect on the resistance of steel to hydrogen assisted cracking. Chromium …

Rf-Sputter Fabrication Of Magnetic Garnet Thin Films And Simulation Modeling For 1-D Magnetic Photonic Crystal Waveguide Devices, Haichun Yang

Dissertations, Master's Theses and Master's Reports - Open

One dimensional magnetic photonic crystals (1D-MPC) are promising structures for integrated optical isolator applications. Rare earth substituted garnet thin films with proper Faraday rotation are required to fabricate planar 1D-MPCs. In this thesis, flat-top response 1D-MPC was proposed and spectral responses and Faraday rotation were modeled. Bismuth substituted iron garnet films were fabricated by RF magnetron sputtering and structures, compositions, birefringence and magnetooptical properties were studied. Double layer structures for single mode propagation were also fabricated by sputtering for the first time.

Multilayer stacks with multiple defects (phase shift) composed of Ce-YIG and GGG quarter-wave plates were simulated by the …

Soft-Decision Equalization Techniques For Frequency Selective Mimo Channels, Shoumin Liu

Dissertations, Master's Theses and Master's Reports - Open

Multi-input multi-output (MIMO) technology is an emerging solution for high data rate wireless communications. We develop soft-decision based equalization techniques for frequency selective MIMO channels in the quest for low-complexity equalizers with BER performance competitive to that of ML sequence detection.

We first propose soft decision equalization (SDE), and demonstrate that decision feedback equalization (DFE) based on soft-decisions, expressed via the posterior probabilities associated with feedback symbols, is able to outperform hard-decision DFE, with a low computational cost that is polynomial in the number of symbols to be recovered, and linear in the signal constellation size. Building upon the probabilistic …

Control Algorithms For Large Scale Adaptive Optics, Piotr Piatrou

Dissertations, Master's Theses and Master's Reports - Open

In this dissertation, the problem of creating effective large scale Adaptive Optics (AO) systems control algorithms for the new generation of giant optical telescopes is addressed. The effectiveness of AO control algorithms is evaluated in several respects, such as computational complexity, compensation error rejection and robustness, i.e. reasonable insensitivity to the system imperfections. The results of this research are summarized as follows:

1. Robustness study of Sparse Minimum Variance Pseudo Open Loop Controller (POLC) for multi-conjugate adaptive optics (MCAO). The AO system model that accounts for various system errors has been developed and applied to check the stability and performance …

Reconstruction Of Anisoplanatic Adaptive Optics Images, Mathieu Aubailly

Dissertations, Master's Theses and Master's Reports - Open

No abstract provided.

Twelve Factors Influencing Sustainable Recycling Of Municipal Solid Waste In Developing Countries , Alexis Manda Troschinetz

Dissertations, Master's Theses and Master's Reports - Open

Sustainable management of solid waste is a global concern, as exemplified by the United Nations Millennium Development Goals (MDG) that 191 member states support. The seventh MDG indirectly advocates for municipal solid waste management (MSWM) by aiming to ensure environmental sustainability into countries’ policies and programs and reverse negative environmental impact. Proper MSWM will likely result in relieving poverty, reducing child mortality, improving maternal health, and preventing disease, which are MDG goals one, four, five, and six, respectively (UNMDG, 2005).

Solid waste production is increasing worldwide as the global society strives to obtain a decent quality of life. Several means …

Quickbird Satellite Imagery For Riparian Management : Characterizing Riparian Filter Strips And Detecting Concentrated Flow In An Agricultural Watershed , Sarah Volkman

Dissertations, Master's Theses and Master's Reports - Open

Riparian ecology plays an important part in the filtration of sediments from upland agricultural lands. The focus of this work makes use of multispectral high spatial resolution remote sensing imagery (Quickbird by Digital Globe) and geographic information systems (GIS) to characterize significant riparian attributes in the USDA’s experimental watershed, Goodwin Creek, located in northern Mississippi. Significant riparian filter characteristics include the width of the strip, vegetation properties, soil properties, topography, and upland land use practices. The land use and vegetation classes are extracted from the remotely sensed image with a supervised maximum likelihood classification algorithm. Accuracy assessments resulted in an …

Corrugated Wood Composite Panels For Structural Decking, Wei Chiang Pang

Dissertations, Master's Theses and Master's Reports - Open

High flexural strength and stiffness can be achieved by forming a thin panel into a wave shape perpendicular to the bending direction. The use of corrugated shapes to gain flexural strength and stiffness is common in metal and reinforced plastic products. However, there is no commercial production of corrugated wood composite panels. This research focuses on the application of corrugated shapes to wood strand composite panels.

Beam theory, classical plate theory and finite element models were used to analyze the bending behavior of corrugated panels. The most promising shallow corrugated panel configuration was identified based on structural performance and compatibility …

Testing Wisconsin Asphalt Mixtures For The 2002 Aashto Mechanistic Design Procedure , Christopher J. Robinette

Dissertations, Master's Theses and Master's Reports - Open

There has been a continuous evolutionary process in asphalt pavement design. In the beginning it was crude and based on past experience. Through research, empirical methods were developed based on materials response to specific loading at the AASHO Road Test. Today, pavement design has progressed to a mechanistic-empirical method. This methodology takes into account the mechanical properties of the individual layers and uses empirical relationships to relate them to performance. The mechanical tests that are used as part of this methodology include dynamic modulus and flow number, which have been shown to correlate with field pavement performance.

This thesis was …

Model Based Experimental Investigation On Powered Gait Orthosis (Pgo), Huojin Cheng

Dissertations, Master's Theses and Master's Reports - Open

Research on rehabilitation showed that appropriate and repetitive mechanical movements can help spinal cord injured individuals to restore their functional standing and walking. The objective of this paper was to achieve appropriate and repetitive joint movements and approximately normal gait through the PGO by replicating normal walking, and to minimize the energy consumption for both patients and the device. A model based experimental investigative approach is presented in this dissertation.

First, a human model was created in Ideas and human walking was simulated in Adams. The main feature of this model was the foot ground contact model, which had distributed …

Active Surgical Positioning Device For A Cochlear Implant Electrode Array, Benjamin Y. Arcand

Dissertations, Master's Theses and Master's Reports - Open

Cochlear implants have been of great benefit in restoring auditory function to individuals with profound bilateral sensorineural deafness. The implants are used to directly stimulate auditory nerves and send a signal to the brain that is then interpreted as sound. This project focuses on the development of a surgical positioning tool to accurately and effectively place an array of stimulating electrodes deep within the cochlea. This will lead to improved efficiency and performance of the stimulating electrodes, reduced surgical trauma to the cochlea, and as a result, improved overall performance to the implant recipient.

The positioning tool reported here consists …

Filtration And Oxidation Characteristics Of A Diesel Oxidation Catalyst And A Catalyzed Particulate Filter : Development Of A 1-D 2-Layer Model, Mohammed Hasan

Dissertations, Master's Theses and Master's Reports - Open

The emissions, filtration and oxidation characteristics of a diesel oxidation catalyst (DOC) and a catalyzed particulate filter (CPF) in a Johnson Matthey catalyzed continuously regenerating trap (CCRT ®) were studied by using computational models. Experimental data needed to calibrate the models were obtained by characterization experiments with raw exhaust sampling from a Cummins ISM 2002 engine with variable geometry turbocharging (VGT) and programmed exhaust gas recirculation (EGR). The experiments were performed at 20, 40, 60 and 75% of full load (1120 Nm) at rated speed (2100 rpm), with and without the DOC upstream of the CPF. This was done to …

Countermeasures Against Scour At Bridge Abutments, Hua Li

Dissertations, Master's Theses and Master's Reports - Open

Scour at bridge abutments can cause damage or failure of bridges and result in excessive repairs, loss of accessibility, or even death. To mitigate abutment scour, both clear-water and live-bed laboratory experiments in a compound channel were performed using parallel walls and spur dikes as countermeasures, respectively. In addition, collars were tested under clear-water conditions only. It was found that both parallel walls and spur dikes can efficiently protect the abutment from scour provided that they are properly designed. Design guidelines were discussed for both countermeasures. Preliminary clear-water tests of collars as countermeasures against scour showed some promising results although …

Study Of Particle Movement In The Nearshore Region Of Lake Superior With Radioisotope Tracers, Yingtao Chai

Dissertations, Master's Theses and Master's Reports - Open

Biogeochemical processes in the coastal region, including the coastal area of the Great Lakes, are of great importance due to the complex physical, chemical and biological characteristics that differ from those on either the adjoining land or open water systems. Particle-reactive radioisotopes, both naturally occurring (²¹⁰Pb, ²¹⁰Po and ⁷Be) and man-made (¹³⁷Cs), have proven to be useful tracers for these processes in many systems. However, a systematic isotope study on the northwest coast of the Keweenaw Peninsula in Lake Superior has not yet been performed.

In this dissertation research, field sampling, laboratory measurements and …