Mechanical Engineering Commons^™

Robust Multichannel Functional-Data-Analysis Methods For Data Recovery In Complex Systems, Jian Sun

Doctoral Dissertations

In recent years, Condition Monitoring (CM), which can be performed via several sensor channels, has been recognized as an effective paradigm for failure prevention of operational equipment or processes. However, the complexity caused by asynchronous data collection with different and/or time-varying sampling/transmission rates has long been a hindrance in the effective use of multichannel data in constructing empirical models. The problem becomes more challenging when sensor readings are incomplete. Traditional sensor data recovery techniques are often prohibited in asynchronous CM environments, not to mention sparse datasets. The proposed Functional Principal Component Analysis (FPCA) methodologies, e.g., nonparametric FPC model and semi-parametric …

Micromechanical Studies Of Intergranular Strain And Lattice Misorientation Fields And Comparisons To Advanced Diffraction Measurements, Lili Zheng

Doctoral Dissertations

Inhomogeneous deformation fields arising from the grain-grain interactions in polycrystalline materials have been evaluated using a crystal plasticity finite element method and extensively compared to neutron diffraction measurements under fatigue crack growth conditions. The roles of intergranular deformation anisotropy, grain boundary damage, and non-common deformation mechanisms (such as twinning for hexagonal close packed crystals) are systematically evaluated. The lattice misorientation field can be used to determine the intragranular deformation behavior in polycrystals or to describe the deformation inhomogeneity due to dislocation plasticity in single crystals. The study of indentation-induced lattice misorientation fields in single crystals sheds lights on the understanding …

Residential Attic Ventilation In A Hot And Humid Climate: Effects Of Increased Ventilation On Thermal Performance And Moisture Control, Stanley Arthur Atherton

Masters Theses

The reality of the effect of natural ventilation in a residential attic cavity has been the topic of many debates and scholarly reports since the 1930’s. The purpose of ventilating an attic cavity is to prevent collection of condensate on the structural surfaces, and to create a thermal buffer between the conditioned space and the ambient air. The current standards are not specific to climate zone, despite the fact that each climate zone may require ventilation for very different reasons.

To address the issue of ventilation effects in a hot and humid climate, a Natural Exposure Testing facility was constructed …

Comparative Study On Posture And Its Influences On Horizontal Ground Reaction Forces Generated By Muscles: Implications For Crouch Gait, Hoa Xuan Hoang

Masters Theses

Crouch gait decreases walking efficiency due to the increased knee and hip flexion during the stance phase of gait. Crouch gait is generally considered to be disadvantageous for patients with cerebral palsy; however, a crouched posture may afford biomechanical advantages that lead some patients to adopt a crouch gait.

To investigate one possible advantage of crouch gait, a musculoskeletal model created in OpenSim was placed in 15 different postures from upright to severe crouch during initial, middle, and final stance of the gait cycle. A series of optimizations were performed for each posture to maximize ground reaction forces for the …

Thermocouple Temperature Measurements For Twin Jet Thermal Mixing, Spero Michael Peters

Masters Theses

Thermocouples are commonly used devices for temperature measurement. This study concerns the implementation of thermocouples to collect thermal mixing data in an environment in which two parallel water jets are mixing. The measurements are taken with the purpose of modeling the jet mixing region so that Computational Fluid Dynamics (CFD) models can be validated against the test data. This thesis covers the design, construction, implementation and evaluation of a thermocouple system for immersion in a water environment to measure the thermal mixing of twin jets.

The measurement system being used is a thermocouple rake whose design and fabrication is covered. …

Dynamics, Electromyography And Vibroarthrography As Non-Invasive Diagnostic Tools: Investigation Of The Patellofemoral Joint, Filip Leszko

Doctoral Dissertations

The knee joint plays an essential role in the human musculoskeletal system. It has evolved to withstand extreme loading conditions, while providing almost frictionless joint movement. However, its performance may be disrupted by disease, anatomical deformities, soft tissue imbalance or injury. Knee disorders are often puzzling, and accurate diagnosis may be challenging. Current evaluation approach is usually limited to a detailed interview with the patient, careful physical examination and radiographic imaging. The X-ray screening may reveal bone degeneration, but does not carry sufficient information of the soft tissue conditions. More advanced imaging tools such as MRI or CT are available, …

In Situ Preconcentration By Ac Electrokinetics For Rapid And Sensitive Nanoparticle Detection, Kai Yang

Doctoral Dissertations

Reducing cost and time is a major concern in clinical diagnostics. Current molecular diagnostics are multi-step processes that usually take at least several hours or even days to complete multiple reagents delivery, incubations and several washing processes. This highly labor-intensive work and lack of automation could result in reduced reliability and low efficiency. The Laboratory-on-a-chip (LOC), taking advantage of the merger and development of microfluidics and biosensor technology, has shown promise towards a solution for performing analytical tests in a self-contained and compact unit, enabling earlier and decentralized testing. However, challenges are to integrate the fluid regulatory elements on a …

The Biglobal Instability Of The Bidirectional Vortex, Joshua Will Batterson

Doctoral Dissertations

State of the art research in hydrodynamic stability analysis has moved from classic one-dimensional methods such as the local nonparallel approach and the parabolized stability equations to two-dimensional, biglobal, methods. The paradigm shift toward two dimensional techniques with the ability to accommodate fully three-dimensional base flows is a necessary step toward modeling complex, multidimensional flowfields in modern propulsive applications. Here, we employ a two-dimensional spatial waveform with sinusoidal temporal dependence to reduce the three-dimensional linearized Navier-Stokes equations to their biglobal form. Addressing hydrodynamic stability in this way circumvents the restrictive parallel-flow assumption and admits boundary conditions in the streamwise direction. …

Haptic Tele-Operation Of Wheeled Mobile Robot And Unmanned Aerial Vehicle Over The Internet, Zhiyuan Zuo

Masters Theses

Teleoperation of ground/aerial vehicle extends operator's ability (e.g. expertise, strength, mobility) into the remote environment, and haptic feedback enhances the human operator's perception of the slave environment. In my thesis, two cases are studied: wheeled mobile robot (MWR) haptic tele-driving over the Internet and unmanned aerial vehicle (UAV) haptic teleoperation over the Internet.
We propose novel control frameworks for both dynamic WMR and kinematic WMR in various tele-driving modes, and for a "mixed" UAV with translational dynamics and attitude kinematics.
The recently proposed passive set-position modulation (PSPM) framework is extended to guarantee the passivity and/or stability of the closed-loop system …

Effects Of Supercooled Water Ingestion On Engine Performance, Rick Hutchings

Masters Theses

An aircraft will encounter freezing rain, snow, and ice during ground operation and flight. In cold conditions, ice may form on th einlet and internal stators and rotors of the gas turbine engine. When ice accumulates on blades (and/or stators), the aerodynamic characteristics of the blades change due to the altered size, shape, and roughness. This change causes the blade to no longer operate at its design point and decreases compressor performance. Therefore, characterization of the aerodynamic performance is required to define the associated losses due to the effects of supercooled liquid water ingestion. This characterization can be accomplished through …

Continuously Variable Rotorcraft Propulsion System: Modelling And Simulation, Naveen Kumar Vallabhaneni

Masters Theses

This study explores the variable speed operation and shift response of a prototype of a two speed single path CVT rotorcraft driveline system. Here a Comprehensive Variable Speed Rotorcraft Propulsion system Modeling (CVSRPM) tool is developed and utilized to simulate the drive system dynamics in steady forward speed condition. This investigation attempts to build upon previous variable speed rotorcraft propulsion studies by:

1) Including fully nonlinear first principles based transient gas-turbine engine model

2) Including shaft flexibility

3) Incorporating a basic flight dynamics model to account for interactions with the flight control system.

Through exploring the interactions between the various …

Development Of A Rigid Body Forward Solution Physiological Model Of The Lower Leg To Predict Non Implanted And Implanted Knee Kinematics And Kinetics, John Kyle Patrick Mueller

Doctoral Dissertations

This dissertation describes the development and results of a physiological rigid body forward solution mathematical model that can be used to predict normal knee and total knee arthroplasty (TKA) kinematics and kinetics. The simulated activities include active extension and weight-bearing deep knee bend. The model includes both the patellofemoral and tibiofemoral joints. Geometry of the normal or implanted knee is represented by multivariate polynomials and modeled by constraining the velocity of lateral and medial tibiofemoral and patellofemoral contact points in a direction normal to the geometry surface.

Center of mass, ligament and muscle attachment points and normal knee geometry were …

Effect Of Unsteady Combustion On The Stability Of Rocket Engines, Tina Morina Rice

Doctoral Dissertations

Combustion instability is a problem that has plagued the development of rocket-propelled devices since their conception. It is characterized by the occurrence of high-frequency nonlinear gas oscillations inside the combustion chamber. This phenomenon degrades system performance and can result in damage to both structure and instrumentation.

The goal of this dissertation is to clarify the role of unsteady combustion in the combustor instability problem by providing the first quantified estimates of its effect upon the stability of liquid rocket engines. The combination of this research with a new system energy balance method, accounting for all dynamic interactions within a system, …

Telerobotic Sensor-Based Tool Control Derived From Behavior-Based Robotics Concepts, Mark William Noakes

Doctoral Dissertations

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Teleoperated task execution for hazardous environments is slow and requires highly skilled operators. Attempts to implement telerobotic assists to improve efficiency have been demonstrated in constrained laboratory environments but are not being used in the field because they are not appropriate for use on actual remote systems operating in complex unstructured environments using typical operators. This work describes a methodology for combining select concepts from behavior-based systems with telerobotic tool control in a way that is compatible …

Solar Decathlon Controls, James Mitchel Routh, Travis Lathrop, Colby Jarrett, Zach Cross

Chancellor’s Honors Program Projects

No abstract provided.

Resonance Testing For Fault Detection Of Steam Generator Heat Transfer Tubing Walls, Michael C. Shannon, John Howington, Jesus Sanchez, Colin Sandidge, Jeremy Townsend, Keith Welsh

Chancellor’s Honors Program Projects

No abstract provided.

Team Tennessee Solar Decathlon Hvac System, Susan Katherine Reid, Kevin Kelly, Brad Hight, Sam Felton

Chancellor’s Honors Program Projects

No abstract provided.

A Thermal Feasibility Study And Design Of An Air-Cooled Rectangular Wide Band Gap Inverter, Jacob Christopher Faulkner

Masters Theses

All power electronics consist of solid state devices that generate heat. Managing the temperature of these devices is critical to their performance and reliability. Traditional methods involving liquid-cooling systems are expensive and require additional equipment for operation. Air-cooling systems are less expensive but are typically less effective at cooling the electronic devices. The cooling system that is used depends on the specific application.

Until recently, silicon based devices have been used for the solid-state devices in power electronics. Newly developed silicon-carbide based wide band gap devices operate at maximum temperatures higher than traditional silicon devices. Due to the permissible increase …

Method For Determination Of Complex Moduli Associated With Viscoelastic Material, Russell Scott Garner

Masters Theses

The aerospace industry is utilizing low cost miniature inertial measurement units (IMUs) that employ Micro Electro-Mechanical Systems (MEMS) technology in an effort to reduce size, weight, and cost of systems. A drawback of these MEMS devices is they are sensitive to vibration, shock and acoustic environments, which limits the usefulness of such devices in the severe environments imposed by many aerospace applications. In an effort to reduce the vibration, shock and acoustic environments experienced by these MEMS devices, the desire to develop passive damping treatments to structural components used to mount these devices. The damping treatments can be applied at …

Cross-Flow, Staggered-Tube Heat Exchanger Analysis For High Enthalpy Flows, Gary L. Hammock

Masters Theses

Cross flow heat exchangers are a fairly common apparatus employed throughout many industrial processes. For these types of systems, correlations have been extensively developed. However, there have been no correlations done for very high enthalpy flows as produced by Arnold Engineering Development Center’s (AEDC) H2 facility. The H2 facility uses a direct current electric arc to heat air which is then expanded through a converging-diverging nozzle to impart a supersonic velocity to the air. This high enthalpy, high temperature air must be cooled downstream by the use of a cross flow heat exchanger.

It is of interest to evaluate the …

Modeling And Analysis Of Turbojet Compressor Inlet Temperature Measurement System Performance, Brian A Binkley

Masters Theses

Accurate measurement of turbine engine compressor inlet total temperature is paramount for controlling engine speed and pressure ratio. Various methods exist for measuring compressor inlet total temperature on turbojet engines with hydromechanical control. One method involves the use of an ejector-diffuser system (eductor) to pull air from the engine inlet in order to measure the incoming total temperature. Analysis of historical test data has revealed that the inlet temperature measurement can be biased at certain flight conditions causing engine mis-scheduling and off-nominal engine operation. This bias is characterized primarily by adverse heat transfer effects and secondly by poor flow quality …

Control And Coordination In A Networked Robotic Platform, Krishna Chaitanya Kalavacharla

Masters Theses

Control and Coordination of the robots has been widely researched area among the swarm robotics. Usually these swarms are involved in accomplishing tasks assigned to them either one after another or concurrently. Most of the times, the tasks assigned may not need the entire population of the swarm but a subset of them. In this project, emphasis has been given to determination of such subsets of robots termed as ”flock” whose size actually depends on the complexity of the task. Once the flock is determined from the swarm, leader and follower robots are determined which accomplish the task in a …

Thermal Feasibility And Performance Characteristics Of An Air-Cooled Axial Flow Cylindrical Power Inverter By Finite Element Analysis, Jonathan Atef Tawfik

Masters Theses

The purpose of the present study is to determine the thermal feasibility of an air-cooled power inverter. The inverter circuitry layout is designed in tandem with the thermal management of the devices. The cylindrical configuration of the air-cooled inverter concept accommodates a collinear axial air blower and a cylindrical capacitor with inverter cards oriented radially between them. Cooling air flows from the axial fan around the inverter cards and through the center hole of the cylindrical capacitor. The present study is a continuation of the thermal feasibility study conducted in fiscal year 2009 for the Oak Ridge National Laboratory to …