Engineering Commons^™

Fabrication Of Large Mechanically Flexible Multi-Layered Pdms Optical Devices, Robert S. Green

Electronic Thesis and Dissertation Repository

Mechanically flexible large area polydimethylsiloxane (PDMS) optical devices are fabricated using soft-lithography techniques based on replica moulding. These non-rigid optical devices can be designed as sheets to act as either light concentrators (collectors) or diffusers (illuminators) based on the position and geometry of micro-optical structures (MOSs) embedded within the sheet or imprinted on its surface. The active surface area of the device can range from less than a sq. cm to several sq. m. The performance of the large area optical device is a function of the location and geometry of micro-optical structures, thickness and shape of the flexible waveguide, …

Controlled Guidance Of Light In Large Area Flexible Optical Waveguide Sheets, Chloë O. Nicholson-Smith

Electronic Thesis and Dissertation Repository

Large surface area, thin, polymer optical waveguides are an emerging technology that enable a wide variety of light collection and illumination systems to be created for passive lighting, solar collectors, and safety lighting for motorized vehicles. This research builds on design of rigid concentrator and diffuser waveguides, proposing and evaluating modifications for the design of a flexible waveguide combining both concentrating and diffusing functionalities. The waveguides are thin, mechanically flexible sheets with thicknesses in the range of mm, and active surfaces from a few cm² to several m². Regions of the functional surface are designed to act …

Numerical Studies For Improving Fracture Toughness Resistance Curve Testing Using Single-Edge (Notched) Tension Specimens, Yifan Huang

Electronic Thesis and Dissertation Repository

The fracture toughness resistance curve, i.e. the J-integral resistance curve (J-R curve) or the crack tip opening displacement resistance (CTOD-R) curves, is widely used in the integrity assessment and strain-based design of energy pipelines with respect to planar defects (i.e. cracks). This thesis deals with issues related to the experimental determination of the J(CTOD)-R curves using the newly-developed single-edge (notched) tension (SE(T)) specimens. In the first study, the plastic geometry factor, i.e. the η_pl factor, used to evaluate J in a J-R curve test based on …

Parametric Design, Modeling, And Optical Evaluation Of Retroreflective Prismatic Structures, Sama Hussein

Electronic Thesis and Dissertation Repository

Retroreflectors (RR) are defined as passive optical structures that redirect incident light to its originating source. Specific types of retroreflectors called inverted cubes (ICs) function through total internal reflection (TIR) and are used in various applications such as measurement tools, traffic signs and automotive rear and side lighting. This thesis aims to model, analyze, fabricate and study a novel type of IC retroreflectors called right triangular prism (RTP). A parametric approach is used to model existing IC geometries from a generic unit cube and is then implemented to model the novel RTP geometry. Those elements are then tested by optical …

Ultraprecise Single Point Inverted Cutting Strategies For Multi-Axis Fabrication Of Right Triangular Prismatic Retroreflectors, Benjamin W. Hamilton

Electronic Thesis and Dissertation Repository

The optical phenomenon of retroreflection (RR) is described as light rays contacting a surface and being redirected back to their originating source. While applications are many and varied, their primary focus is safety in low-light conditions, and the focus of this research is toward automotive applications. Few geometric shapes are capable of retroreflection. Among them are the lens-and-mirror, and cube corner geometry; however, the right triangular prism (RTP) has been introduced as a viable alternative. This study demonstrates a more efficient fabrication technology when compared to current industry practices.

The ultraprecise single point inverted cutting (USPIC) technology was envisioned as …

Hybrid Magneto-Rheological Actuators For Human Friendly Robotic Manipulators, Masoud Moghani

Electronic Thesis and Dissertation Repository

In recent years, many developments in the field of the physical human robot interaction (pHRI) have been witnessed and significant attentions have been given to the subject of safety within the interactive environments. Ensuring the safety has led to the design of the robots that are physically unable to hurt humans. However, Such systems commonly suffer from the safety-performance trade-off. Magneto-Rheological (MR) fluids are a special class of fluids that exhibit variable yield stress with respect to an applied magnetic field. Devices developed with such fluids are known to provide the prerequisite requirements of intrinsic safe actuation while maintaining the …

The Effect Of Mesh-Type Bubble Breakers On Two-Phase Vertical Co-Flow, Alan Kalbfleisch

Electronic Thesis and Dissertation Repository

It is proposed that mesh-type bubble breakers can be used in two-phase gas-liquid vertical cocurrent pipe flow to enhance the heat and mass transfer rates. Two experimental studies were performed to investigate the effect of mesh-type bubble breakers with varying geometries on two-phase flow behaviour. The first used highspeed imaging to measure bubble size and observe the resulting flow regime for two-phase vertical co-flow consisting of air and water. A Froude number correlation that can be used to predict the bubble size generated by mesh-type bubble breakers is proposed. Flow regime maps for two-phase flow in the presence of bubble …

Characterization Of Mean And Turbulent Flow Over Complex Topography Under Various Inflow And Geometric Configurations, Ryan J. Kilpatrick

Electronic Thesis and Dissertation Repository

An experimental investigation of flow over a complex topography was undertaken to study the influence of inflow conditions including Reynolds number, upstream roughness, and inflow shear profile on mean and turbulent flow behaviour.

Large-scale physical testing was employed over the escarpment of a hill, covering a Reynolds number range of 3.6×10⁴ to 5.2×10⁵. Measurements taken using Particle Image Velocimetry (PIV) and Cobra Probes were analyzed in terms of mean and turbulent statistics. Coherent structures were characterized through Proper Orthogonal Decomposition (POD).

The results show that the Reynolds number had little effect on the flow behaviour, while the …

Thermal Modeling For Light Armored Vehicle, Marc-André H. Brooks

Electronic Thesis and Dissertation Repository

Light Armored vehicles are required to operate in a variety of extremely hot and arid climates. As such, these vehicles are often subject to large heat gains due to environmental factors. The current systems employed for vehicle cooling do not always perform to the levels that are required, mainly due to the lack of a good estimate of the cooling load. A thermal analog circuit was created which separated each of the heat sources into its own module. Using material properties provided by General Dynamics Land Systems as well as information from acquired from CFD studies and ASHRAE, the values …

Experimental Investigation Of The Melting Behavior And The Transient Heat Transfer In A Phase Change Material (Pcm), Mohammad A. Bashar

Electronic Thesis and Dissertation Repository

Phase change materials (PCMs) used in thermal energy storage (TES) system as heat storage media can play crucial role in various engineering applications. PCMs have the inherent ability to store large amount of heat by exploiting their heat of fusions, predominantly during their solid-liquid phase-change period. The present study reports an experimental investigation on the melting process in a PCM and the associated heat transfer in a transient manner. The experiments were conducted in a rectangular chamber filled with paraffin wax used as the PCM and, a cylindrical copper tube with different geometries and orientations as the heat source.

The …

Numerical Investigation Of Full Scale Thunderstorm Downbursts: A Parametric Study And Comparison To Meteorological Model, Christopher Oreskovic

Electronic Thesis and Dissertation Repository

A series of Large Eddy Simulations using an atmospheric meteorological cloud model have been used to investigate the important geometric and thermal parameters that influence a thunderstorm downburst outflow, as it pertains specifically to the idealized cooling source model. A separate set of Large Eddy Simulations make use of the same idealized cooling source model, in a realistic atmospheric base state using real field sounding data, in an attempt to make a quantifiable comparison to a downburst from a full cloud simulation. Randomness has been added to the cooling source forcing function to mimic the thermal variation in a real …

A Model For Complex Heat And Mass Transport Involving Porous Media With Related Applications, Furqan A. Khan

Electronic Thesis and Dissertation Repository

Heat and mass transfer involving porous media is prevalent in, for example, air-conditioning, drying, food storage, and chemical processing. Such applications require non-equilibrium heat and mass (or moisture) transfer modeling inside porous media in conjugate fluid/porous/solid framework. Moreover, modeling of turbulence and turbulent heat and mass transfer becomes essential for many applications. A comprehensive literature review shows a scarcity of models having such capabilities. In this respect, the objectives of the present thesis are to: i) develop a formulation that simulates non-equilibrium heat and mass transfer in conjugate fluid/porous/solid framework, ii) demonstrate the capabilities of the developed formulation by simulating …

Optimizing The Rehabilitation Of Elbow Lateral Collateral Ligament Injuries, Ranita Harpreet Kaur Manocha

Electronic Thesis and Dissertation Repository

Elbow lateral collateral ligament (LCL) injuries frequently arise following trauma, and can result in disabling instability. Typically such injuries are managed with immobilization followed by a graduated exercise regime; however there is minimal biomechanical evidence to support current treatment protocols. This investigation examines the in vitro effectiveness of several rehabilitation techniques using a custom elbow motion simulator. It was found that active range of motion is safest in the overhead position (n = 7). Early motion in this position may reduce the incidence of elbow stiffness without compromising ligament healing following LCL injury. Forearm pronation and active motion stabilize …

Application Of Natural Convection For Photovoltaic Cooling And Photocatalytic Disinfection, Usman J. Rajput

Electronic Thesis and Dissertation Repository

Two investigations for improving renewable technologies are engaged. First is the examination of the enhancement of heat transfer at the rear of a hot photovoltaic panel by natural convection using various configurations and the other is analyzing a new photocatalytic collector for water heating and cleaning. A 20 Watt polycrystalline panel is exposed to indoor simulated solar light, under constant ambient temperature and stagnant wind conditions. Three configurations are considered: a partial heat sink, a water cavity and a water channel. The experimentally obtained convective heat transfer coefficients are 4.4 W•m^-2•K^-1 at the rear of the bare …

Development Of An Autonomous Robotic Mushroom Harvester, Nikita Alexeevich Kuchinskiy

Electronic Thesis and Dissertation Repository

The process of development of a new robot is one of the modern technological arts. This process involves multiple complex steps and recursive approach. In this project, a solution for automatic harvesting of mushrooms is developed. In order to design an effective solution, it is necessary to explore and take into consideration the limitations of grasping very soft and fragile objects (particularly mushrooms). We will elaborate several strategies of picking and analyze each strategy to formulate the design requirements, develop a solution, and finally, evaluate the efficiency of the proposed solution in actual farm conditions for real mushrooms. The mushroom …

Use Of Natural Instability For Enhancement Of Flow Mixing In Annuli, Amirreza Seddighi

Electronic Thesis and Dissertation Repository

A technique has been proposed to increase flow mixing in annuli by means of vortex generation. Corrugations in the form of axisymmetric ribs are placed at the walls of annulus to modulate the axial flow which can potentially induce vortex instabilities. Unlike other vortex generation methods which suffer from relatively high pressure losses, this technique is expected to cause less pressure drop. Spectral algorithm based on Fourier and Chebyshev expansions has been used to study the stationary state and its stability. Due to the irregularities of the boundaries, the immersed boundary conditions (IBC) method is used to enforce the flow …