Mechanical Engineering Commons^™

Hybrid Attitude Control And Estimation On So(3), Soulaimane Berkane

Electronic Thesis and Dissertation Repository

This thesis presents a general framework for hybrid attitude control and estimation design on the Special Orthogonal group SO(3). First, the attitude stabilization problem on SO(3) is considered. It is shown that, using a min-switch hybrid control strategy designed from a family of potential functions on SO(3), global exponential stabilization on SO(3) can be achieved when this family of potential functions satisfies certain properties. Then, a systematic methodology to construct these potential functions is developed. The proposed hybrid control technique is applied to the attitude tracking problem for rigid body systems. A smoothing mechanism is proposed to filter out the …

Free-Surface Wall-Jet Flow At Moderate Reynolds Number As Applied To Slot And Blade Coating, Mohammad Tanvir Hossain

Electronic Thesis and Dissertation Repository

The flow of a two-dimensional steady wall jet observed in the slot and blade coating processes has been examined theoretically near the channel exit. The Newtonian free surface jet emerges from a channel and deposits onto an infinite moving wall with an adverse or favorable pressure gradient applied inside the channel. The Reynolds number considered is within the moderate range, and fully developed Couette-Poisueille flow conditions are assumed to prevail far upstream inside the channel. The effects of inertia and pressure gradient on the velocity, the shape of the free surface, and the stress are emphasized. It is found that …

Metal Sulfides As Anode For Lithium Ion And Sodium Ion Battery, Ali Abdulla

Electronic Thesis and Dissertation Repository

Abstract

Nanomaterials have been studied intensively in the last decades due to their unique physical and chemical properties and their potential for applications in different domains. Among these applications, energy storage has become the center of focus by many research groups and companies to develop high efficiency and reliable energy devices such as the commercial lithium ion batteries (LIBs). However, LIBs has not yet met the growing requirements of the high demand for increasing energy density. More efforts are requested to improve the performance of the batteries by designing better electrode materials and increasing the battery safety. Another type of …

Influence Of Scapular Notching On Contact Mechanics And Simulator Wear Of Reverse Total Shoulder Arthroplasty Implants, Michael William Griffiths

Electronic Thesis and Dissertation Repository

Scapular notching is a common complication of reverse total shoulder arthroplasty (RTSA) wherein the predominant focus of current literature has been on changes in osseous anatomy. However, the implications on RTSA performance from the damaged humeral cup is largely unknown. Therefore the present work describes the effects of the initiation and propagation of the humeral cup defect resulting from scapular notching through the use of finite element modeling and wear simulation, in order to assess changes in RTSA contact mechanics and tribological properties. A significant decrease in articular contact area and increase in maximum contact stress values was found for …

Surface Topography Formation And Thermographic Analysis In Laser Polishing Of H13 Tool Steel, Joshua D. Miller

Electronic Thesis and Dissertation Repository

Laser polishing, in its simplest form, is the melting of a small layer of material via laser radiation. This creates a small molten pool which is re-distrusted across the surface, resulting in a much smoother finished surface. Although this process has been around for decades now, there has been a recent insurgence into industrial applications. Despite this, the phenomena that occur during the process are still not fully understood. Therefore, increasing the knowledge surrounding the process would be ideal.

To accomplish this, various input parameters of the process are altered to analyze the effect on the finished polished surface. Through …

Influence Of Turbulence On The Aerodynamics Of Low-Rise Buildings, Fakhruzzaman Arif

Electronic Thesis and Dissertation Repository

During extreme wind events, roofing failures may lead to damage of the whole structure. In order to alleviate the effect, surface pressure coefficients on the roofs have been extensively investigated. This research aims to determine the roof pressures acting on low-rise buildings with consideration of the effects of turbulence (terrain). Pressure measurements, as well as wind speed data, were taken at the Boundary Layer Wind Tunnel Laboratory (BLWTL) of the University of Western Ontario (UWO) to examine the influence of turbulence level (i.e., terrain condition) on the critical wind directions corresponding to the largest surface roof pressure coefficients for various …

The Development And Numerical Modelling Of A Representative Elemental Volume For Packed Sand, Ashraf Thabet

Electronic Thesis and Dissertation Repository

The motivation of this thesis is the development of simple microscopic-scale model (representative elemental volume; REV) that can be used to conduct flow and heat transfer simulations from which closure coefficients can be established for the volume-averaged transport equations for porous media (packed bed). The thesis provides a brief introduction to the computational technique adopted for the geometric generation of the REV (YADE), followed by a parametric study undertaken to reveal the minimum number of particles inside the REV that are required to mimic the appropriate physics. Additional analysis was conducted with the goal of determining the influence of deviation …

3d Printing Of Functional Materials: Surface Technology And Structural Optimization, Dongxing Zhang

Electronic Thesis and Dissertation Repository

There has been a surge in interest of 3D printing technology in the recent 5 years with respect to the equipment and materials, because this technology allows one to create sophisticated and customized parts in a manner that is more efficient regarding both material and time consumption. However, 3D printing has not yet become a mainstream technology within the established manufacturing routes. One primary factor accounting for this slow progress is the lack of a broad variety of 3D printable materials, resulting in limited functions of 3D printed parts.

To bridge this gap, I present an integrated strategy to fabricate …

Numerical Simulations Of Two-Phase Flows In The Liquid Solid Circulating Fluidized Bed, Hao Luo

Electronic Thesis and Dissertation Repository

The liquid-solid circulating fluidized bed (LSCFB) has many potential applications in biochemical and petroleum industries, as well as in wastewater treatments, given its higher contact efficiency and being able to accommodate two reactions under one system. With extensive experimental results becoming available, there is clearly a need for computational fluid dynamics (CFD) modeling to expand our understandings of LSCFBs and to predict the hydrodynamic behaviors of the two-phase flows within LSCFB.

In this research, the Eulerian-Eulerian two-phase model combined with the kinetic theory for the granular phase is applied to simulate the two-phase flows in LSCFBs. The key factors affecting …

Experimental Measurements Of Far Field Cough Airflows Produced By Healthy And Influenza- Infected Human Subjects, Ahmed Faraj Alarbi Mohamed

Electronic Thesis and Dissertation Repository

The present work details an experimental study of the cough airflow fields produced by subjects infected with influenza and when they are convalescent, together with data from healthy cohorts. The PIV and HWA measurements were taken far downstream at 1 m from the source within a cough chamber, along with droplet sampling at two different locations and nasal swabs from the sick subjects. The measured data over different seasons were used to evaluate and compare the results from sick, convalescent and healthy subjects. Although a total of 8 sick participants from winter 2014 and 2017 yielded positive nasal swab analysis, …

The Onset Of Convection In Rarefied Gases, Md Asif Zobaer

Electronic Thesis and Dissertation Repository

The onset of convection in the Rayleigh-Bénard problem for a monatomic rarefied gas at small Knudsen number has been investigated. Compressibility-induced density variations have been considered without imposing any restriction on the magnitude of temperature difference. A linear temporal stability analysis has been conducted for a compressible slip-flow model considering a Maxwellian gas and the dispersion relation is calculated using a Chebyshev collocation method. A neutral stability curve obtained in the Froude-Knudsen number plane marks transition to convection from a pure conduction state. The critical wave number observed for the onset of convection is in good agreement with the existing …

Ultraprecise Single Point Inverted Cutting Of Right Triangular Prismatic Retroreflectors: Process Enhancements And Cutting Mechanics, Nicolas Milliken

Electronic Thesis and Dissertation Repository

Automotive lighting industry relies on retroreflective components to increase driver awareness in low-light conditions since their primary functionality is to return incident light back to the source and/or observer with minimal scatter.

Presently, industry makes use of conventional pin-bundling techniques for the fabrication of the retroreflective components. This method is time consuming, labour intensive, and restrictive with respect to the design process. For these reasons, the ultraprecise single point inverted cutting (USPIC) technology was developed as an efficient alternative for manufacturing novel right triangular prismatic (RTP) retroreflective structures.

This thesis outlines a number of enhancements that improve both the quality …

Additive Manufacturing Process Of 3d Polyaniline Transducers Via Direct Ink Writing, Frederick Benjamin Holness

Electronic Thesis and Dissertation Repository

Electroactive polymers exhibit a change in properties, typically size or shape, in response to electrical stimuli. One class of electroactive polymer of particular interest are the conjugated polymers, whose conjugated backbone structure imparts electrical conductivity. However, this structure imposes processing limitations restricting their form to 2D structures. To overcome this, we develop specially formulated polyaniline- based blends via counter-ion induced thermal doping for the fabrication of 3D conductive structures via direct ink writing. This approach employs multi-material extrusion for the production of structures with passive and active features, rapid device fabrication, and improved design freedom. A model of the thermal …

Flow Characterization Under Idealized Stenosis Geometry And Performance Assessment Of The Hemodynamic Flow Facility, Marin Vratonjic

Electronic Thesis and Dissertation Repository

It is well known that regions inside the human arterial network susceptible to atherosclerosis experience a complex flow environment. Endothelial Cells (ECs) lining the inner wall of arteries are sensors to spatially and temporally varying shear stress (i.e. wall shear stress gradients). This complex force-loading can disrupt local cell-to-cell attachment regions triggering a cascade of biological events leading to the formation of atherosclerotic lesions. Consequently, researchers predominantly use a Parallel Plate Flow Chamber (PPFC) to study the hemodynamic-cell cycle relationship due to its simplicity and ability to achieve a two-dimensional fully-developed steady laminar flow across the cell monolayer. Researchers also …

Full-Scale And Wind Tunnel Investigation Of The Flow Field Over A Coastal Escarpment, Julien Lotufo

Electronic Thesis and Dissertation Repository

A multiscale experimental approach, consisting of full-scale measurements and physical modeling in a laboratory environment, was conducted to investigate the flow field over a coastal escarpment on the Wind Energy Institute of Canada’s research and development wind park. The influence of sea breeze inflow conditions, thermal stability and local topographic features on the flow field were examined.

The results of the full-scale study show that the near surface flow field is significantly influenced by the sea breeze circulatory coastal flow regime, creating larger shear layers with a smaller recirculation regions compared to cases of typical boundary layer flow typical boundary …

P26. Global Exponential Stabilization On So(3), Soulaimane Berkane

Western Research Forum

Global Exponential Stabilization on SO(3)

Effects Of Turbulence On The Separating-Reattaching Flow Above Surface-Mounted, Three-Dimensional Bluff Bodies, Abul Fahad Akon

Electronic Thesis and Dissertation Repository

Investigations of separated and reattaching flows over three-dimensional bluff bodies in turbulent boundary layers are important because of the large aerodynamic loads that these flows cause. For example, roofs of low-rise buildings are vulnerable to this kind of wind loading. Turbulence in the upstream flow affects the pressure distributions and the mean size of separation bubbles formed on bluff body surfaces. Whereas a number of studies have focussed on two-dimensional separation bubbles and surface pressures, a comprehensive understanding of the surface pressures and the separating-reattaching flows in relation to the turbulence in the incident boundary layers for surface-mounted, three-dimensional bluff …

Convection In Corrugated Slots, Seyed Arman Abtahi

Electronic Thesis and Dissertation Repository

This thesis consists of two parts. The first part deals with the development of proper methodology, i.e. a spectrally accurate algorithm suitable for analysis of convection problems in corrugated slots. The second part is devoted to the study of natural convection in corrugated slots.

The algorithm uses the immersed boundary conditions (IBC) concept to deal with the irregular form of the solution domain associated with the presence of corrugated plates. The field equations are discretized on a regular domain surrounding the flow domain using Fourier expansions in the horizontal direction and Chebyshev expansions in the vertical direction. The boundary conditions …

Dynamic Coupling Of Phase-Heat And Mass Transfer In Porous Media And Conjugate Fluid/Porous Domains, Mahmoud Mohamed Mostafa Elhalwagy, Anthony G. Straatman

Mechanical and Materials Engineering Publications

No abstract provided.