Digital Commons Network^™

Versatile And Robust Non-Iterative Coupling Algorithm For Vehicle-Structure Interaction, Arya Datta

Theses and Dissertations

The dynamic analysis of the vehicle-structure interactions can be extremely computationally expensive. A general non-iterative coupling algorithm based on the substructure approach has been presented. It retains the advantage of the substructure approach that smaller subsystems are solved instead of a large system, which is usually solved when monolithic systems are solved. However, the advantage of using this general coupling approach is that it is non-iterative in nature, instead of the substructure approach that usually uses iterative procedure. The general coupling algorithm developed has been implemented to analyze dynamic interactions between the vehicle and the structure, both in two and …

Dry Reforming Of Methane Using Microwave Irradiated Metal Oxide/Coal Char Catalysts, Anthony Carter

Graduate Theses, Dissertations, and Problem Reports

This research focuses on the synthesis of both shaped and amorphous powder materials, the combination of these materials with dried Powder River Basin (PRB) coal char, and their reactionary properties with methane and carbon dioxide gasses with conventional and microwave (MW) heating. The first goal of this project was to synthesize shaped micro and nano sized particles with ideal dielectric properties for converting electromagnetic energy into heat and proven capabilities of activating methane. These particles were synthesized via solvothermal, hydrothermal, and co-preceptory treatments alone and onto the surface of dried PRB coal char. PRB is a sub-bituminous, low-ranking coal (LRC) …

Increasing Isolation Between Closely Spaced X-Band Planar Transmit/Receive Antennas, Jacob Bartschi

Undergraduate Honors Theses

Coupling between Tx/Rx antennas is a common and much-researched problem that is especially difficult when the antennas both placed close together and on the same plane. New systems with smaller footprints require this kind of placement while still maintaining the same levels of isolation as before. Traditional solutions for coupling involve large and heavy machined parts that are unsuited to compact systems. Many techniques have been proposed over the decades, but few have been applied to X-band antennas in closely spaced configurations. This thesis investigates those techniques, applies them to closely spaced X-band antennas, and compares them to conventional methods …

On Axon-Axon Interaction Via Currents And Fields, Aman Chawla

USF Tampa Graduate Theses and Dissertations

In this dissertation, we investigate coupling between axons in a tract, when the tract has an arbitrary cross-section, with the coupling being mediated by currents as well as electric fields. Under the current mediated setting, we develop a new master equation which captures the relative axonal geometry, specifically, the axon inclinations θ_i and the inter-axon distances W_ip and perform a number of simulations. We observe synchronization in our simulations of axons with differing diameters and separation-dependent coupling delays in the case of non-trivial tract geometries. For the field-mediated interaction setting, we determine the electric near-field of a firing …

Modeling Of Frame Structures Undergoing Large Deformations And Large Rotations, Hui Liu

Open Access Dissertations

Numerical simulation of large-scale problems in structural dynamics, such as structures subject to extreme loads, can provide useful insights into structural behavior while minimizing the need for expensive experimental testing for the same. These types of problems are highly non-linear and usually involve material damage, large deformations and sometimes even collapse of structures. Conventionally, frame structures have been modeled using beam-frame finite elements in almost all structural analysis software currently being used by researchers and the industry. However, there are certain limitations associated with this modeling approach. This research focuses on two issues, in particular, of modeling frame structures undergoing …

Testing Feasibility Of Inductive Power Coupling For Modern Applications, Andrew Burman

BioResource and Agricultural Engineering

This project takes two bifilar tesla coils and uses them to find a % efficiency of power transfer as distances between the coils decrease. The reason this experiment is being conducted is to find possible implications for wireless charging of vehicles using similar style coils. This project conducted experiments on 60 Hz, 400 Hz, and 1 kHz frequencies for a small input signal. The general conclusion is that as the frequency increases more power can be transferred and higher efficiency of power transfer is seen. This project also concluded that it could be possible to get higher efficiency at a …

Design Of A Mobile Underwater Charging System, Brian R. Page

Dissertations, Master's Theses and Master's Reports

Autonomous Underwater Vehicles (AUVs) are extremely capable vehicles for numerous ocean related missions. AUVs are energy limited, resulting in short mission endurance on the scale of hours to days. Underwater Gliders (UGs) are able to operate on the order of months to years by using nontraditional propulsion methods. UGs, however, are unable to perform missions requiring high speed or direct forward motion due to the nature of their buoyancy driven motion. This work reviews the current state of the art in recharging AUVs and offers an underwater recharging network concept at a significantly reduced cost to traditional methods. The solution …

High Temperature Flow Solver For Aerothermodynamics Problems, Huaibao Zhang

Theses and Dissertations--Mechanical Engineering

A weakly ionized hypersonic flow solver for the simulation of reentry flow is firstly developed at the University of Kentucky. This code is the fluid dynamics module of known as Kentucky Aerothermodynamics and Thermal Response System (KATS). The solver uses a second-order finite volume approach to solve the laminar Navier– Stokes equations, species mass conservation and energy balance equations for flow in chemical and thermal non-equilibrium state, and a fully implicit first-order backward Euler method for the time integration. The hypersonic flow solver is then extended to account for very low Mach number flow using the preconditioning and switch of …

Auxiliary Roles In Stt-Mram Memory, Jayita Das

USF Tampa Graduate Theses and Dissertations

Computer memories now play a key role in our everyday life given the increase in the number of connected smart devices and wearables. Recently post-CMOS memory technologies are gaining significant research attention along with the regular ones. Spin Transfer Torque Magnetoresistive RAM (STT-MRAM) is one such post-CMOS memory technology with a rapidly growing commercial interest and potential across diverse application platforms. Research has shown the ability of STT-MRAM to replace different levels of memory hierarchy as well. In brief, STT-MRAM possesses all the favorable properties of a universal memory technology. In this dissertation we have explored the roles of this …

Design Of A Passive Ankle Prosthesis With Powered Push-Off Using A Cam Timing Mechanism, Jacob J. Rice

Master's Theses (2009 -)

This thesis presents the design and simulation results of the CamWalk, a novel passive prosthetic ankle that has mechanical behavior similar to that for a natural ankle. The CamWalk uses a compression spring network that allows coupling between two degrees of freedom; one for translation along the leg and another for rotation about the ankle joint. When walking, potential energy from the person's weight is stored in the spring network in deflection along the leg. The energy is released by the network as rotation of the foot. The amount of translational work that is converted to rotational work about the …

Simulating High Flux Isotope Reactor Core Thermal-Hydraulics Via Interdimensional Model Coupling, Adam Ross Travis

Masters Theses

A coupled interdimensional model is presented for the simulation of the thermal-hydraulic characteristics of the High Flux Isotope Reactor core at Oak Ridge National Laboratory. The model consists of two domains—a solid involute fuel plate and the surrounding liquid coolant channel. The fuel plate is modeled explicitly in three-dimensions. The coolant channel is approximated as a two-dimensional slice oriented perpendicular to the fuel plate’s surface. The two dimensionally-inconsistent domains are linked to one another via interdimensional model coupling mechanisms. The coupled model is presented as a simplified alternative to a fully explicit, fully three-dimensional model. Involute geometries were constructed in …

A Study Of Acoustic Boom Generation Due To Vibro-Acoustic Coupling In Passenger Cars, Mayuresh Pathak

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

This thesis aims at understanding the vibro-acoustic behavior related to vehicle boom in passenger cars. Acoustic boom in the 40 Hz frequency range is studied on a 2013 Chevrolet Cruze LTZ model. Impact testing, full vehicle structural and acoustic modal tests are first performed to understand, locate and test the boom phenomenon and the fluid-structure interaction between the vehicle structure and acoustic cavity. Later, different iterations like effect of door cavities, trunk cavity and rear seats are also tested to understand their participation. LMS Test.Lab software is used for data acquisition, processing and analysis of the test results.

Finite Element …

Predictive Maturity Of Inexact And Uncertain Strongly Coupled Numerical Models, Ismail Farajpour

All Dissertations

The Computer simulations are commonly used to predict the response of complex systems in many branches of engineering and science. These computer simulations involve the theoretical foundation, numerical modeling and supporting experimental data, all of which contain their associated errors. Furthermore, real-world problems are generally complex in nature, in which each phenomenon is described by the respective constituent models representing different physics and/or scales. The interactions between such constituents are typically complex in nature, such that the outputs of a particular constituent may be the inputs for one or more constituents. Thus, the natural question then arises concerning the validity …

Transient Small Wind Turbine Tower Structural Analysis With Coupled Rotor Dynamic Interaction, George R. Katsanis

Master's Theses

Structural dynamics is at the center of wind turbine tower design - excessive vibrations can be caused by a wide range of environmental and mechanical sources and can lead to reduced component life due to fatigue, noise, and impaired public perception of system integrity. Furthermore, periodic turbulent wind conditions can cause system resonance resulting in significantly increased structural loads. Structural vibration issues may become exacerbated in small wind applications where the analytical and experimental resources for system verification and optimization are scarce. This study combines several structural analysis techniques and packages them into a novel and integrated form that can …

Multi-Physics Modeling Of Geomechanical Systems With Coupled Hydromechanical Behaviors, Ahmad Mohamed

Electronic Theses and Dissertations

Geotechnical structures under realistic field conditions are usually influenced with complex interactions of coupled hydromechanical behavior of porous materials. In many geotechnical applications, however, these important coupled interactions are ignored in their constitutive models. Under coupled hydromechanical behavior, stress in porous materials causes volumetric change in strain, which causes fluid diffusion; consequently, pore pressure dissipates through the pores that results in the consolidation of porous material. The objective of this research wasto demonstrate the advantages of using hydromechanical models to estimate deformation and pore water pressure of porous materials by comparing with mechanical-only models. Firstly, extensive literature survey was conducted …

Method Of Moments Analysis Of An Aperture In A Thick Ground Plane, Ahmet Burak Olcen

Electrical Engineering and Computer Science - Dissertations

The problem of electromagnetic scattering from and transmission through an arbitrarily shaped aperture is considered. The aperture is in a thick infinite perfectly conducting ground plane. The conducting walls of the cavity inside the ground plane are of arbitrary shape. The apertures at both ends of the cavity are also of arbitrary shape. The structure is illuminated by an incident plane electromagnetic wave. The Green's function for this complicated problem is almost impossible to determine. Therefore the surface equivalence principle is used to reduce this complex problem into three simpler ones. Each such problem consists of equivalent surface currents radiating …

A New Method For Coupling 2d And 3d Deterministic And Stochastic Radiation Transport Calculations, Joel Aaron Kulesza

Masters Theses

The objective of this body of work was to produce a code system capable of processing boundary angular flux data from discrete ordinates calculations in 2D and 3D Cartesian and cylindrical geometries into cumulative probability density functions that can be used with a Monte Carlo radiation transport code to define neutron and photon initial positions, directions, and energies. In order to accomplish this goal, the DISCO (DetermInistic-Stochastic Coupling Operation) code was created to interface between the DORT and TORT deterministic radiation transport codes and the MCNP stochastic radiation transport code. DISCO introduces new methods to use the boundary angular flux …

A Wind Tunnel Technique For The Identification Of Ship Airwake/Rotor Downwash Coupling, Stargel R. Doane

Mechanical & Aerospace Engineering Theses & Dissertations

A wind tunnel study is performed to analyze the interaction between ship airwakes and helicopter rotor downwash. This interaction is of interest to naval aviators and researchers as this phenomenon is thought to limit helicopter flight envelopes and increase the overall difficulty of maritime rotorcraft operations. In this study, a 1/50th scale simplified naval frigate model and appropriately scaled rotor model are used for all experimental work. A rotor thrust survey was conducted in the immediate vicinity of the landing deck. Two dimensional and stereo particle image velocimetry surveys and rotor thrust measurements with various rotor and ship configurations were …

Aperture Coupling And Penetration In Various Configurations, Jason Keen

All Dissertations

The problem of a slot in a perfectly conducting surface is addressed for a variety of configurations using both integral equation and transmission line techniques. The use of Bethe hole theory to model short slots is discussed and utilized where appropriate. Primary problems of discussion are a slot array, wires coupling through slots in a ground plane, and wires coupling through slots in a bent ground plane. Additionally, the use of the extended BLT formulation for incorporation of slot effects in a transmission line problem is addressed. In this manuscript, the work of Bethe is extended to include cross-aperture coupling …

Tooth Engagement Evaluation Of Involute Spline Couplings, Robert R. Robins

Theses and Dissertations

Spline couplings are used in applications involving high torque; however, due to variations in teeth clearances, all teeth in spline couplings do not engage simultaneously, causing some of the teeth to carry a disproportionately large portion of the total load. Variations in tooth-to-tooth clearances mean the first pair of teeth to engage will carry more load and fail sooner. This has lead to an industry practice of designing splines around the criteria that only 25-50% of the teeth on a spline coupling will engage and carry the load, and the load is generally assumed to be uniformly distributed. This research …

Analysis Of Complexity And Coupling Metrics Of Subsystems In Large Scale Software Systems, Harish Ramakrishnan

Electronic Theses and Dissertations

Dealing with the complexity of large-scale systems can be a challenge for even the most experienced software architects and developers. Large-scale software systems can contain millions of elements, which interact to achieve the system functionality. Managing and representing the complexity involved in the interaction of these elements is a difficult task. We propose an approach for analyzing the reusability, maintainability and complexity of such a complex large-scale software system. Reducing the dependencies between the subsystems increase the reusability and decrease the efforts needed to maintain the system thus reducing the complexity of the system. Coupling is an attribute that summarizes …

Coupling Of Hydrodynamic And Wave Models For Storm Tide Simulations: A Case Study For Hurricane Floyd (1999), Yuji Funakoshi

Electronic Theses and Dissertations

This dissertation presents the development of a two-dimensional St. Johns River model and the coupling of hydrodynamic and wave models for the simulation of storm tides. The hydrodynamic model employed for calculating tides and surges is ADCIRC-2DDI (ADvanced CIRCulation Model for Shelves, Coasts and Estuaries, Two-Dimensional Depth Integrated) developed by Luettich et al. (1992). The finite element based model solves the fully nonlinear shallow water equations in the generalized wave continuity form. Hydrodynamic applications are operated with the following forcings: 1) astronomical tides, 2) inflows from tributaries, 3) meteorological effects (winds and pressure), and 4) waves (wind-induced waves). The wave …

Preliminary Study On The Impact Of Impingement On The Effectiveness Of Film Cooling In The Presence Of Gas Path Pressure Gradient, Anil Peravali

Electronic Theses and Dissertations

Impingement is the most commonly used method of cooling in the hot stages of gas turbines. This is often combined with film cooling to further increase the cooling performance. The mainstream flow where in the coolant films discharge often has large stream wise pressure variations. All existing studies on coupled film and impingement cooling concentrated on the effect of the film depletion on the impingement heat transfer. This study investigates the impact of impingement on film cooling, where the jets impinging on a flat plate are depleted through arrays of film cooling holes in the presence of pressure gradient in …