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Articles 1051 - 1080 of 1700
Full-Text Articles in Mechanical Engineering
Burnout, No, Flame Temperature, And Radiant Intensity From Oxygen-Enriched Combustion Of A Hardwood Biomass, Joshua David Thornock
Burnout, No, Flame Temperature, And Radiant Intensity From Oxygen-Enriched Combustion Of A Hardwood Biomass, Joshua David Thornock
Theses and Dissertations
Increasing concern for energy sustainability has created motivation for the combustion of renewable, CO2 neutral fuels. Biomass co-firing with coal provides a means of utilizing the scaled efficiencies of coal with the lower supply availability of biomass. One of the challenges of co-firing is the burnout of biomass particles which are typically larger than coal but must be oxidized in the same residence time. Larger biomass particles also can increase the length of the radiative region and alter heat flux profiles. As a result, oxygen injection is being investigated as a means of improving biomass combustion performance.An Air Liquide designed …
Developing An Architecture Framework For Cloud-Based, Multi-User, Finite Element Pre-Processing, Jared Calvin Briggs
Developing An Architecture Framework For Cloud-Based, Multi-User, Finite Element Pre-Processing, Jared Calvin Briggs
Theses and Dissertations
This research proposes an architecture for a cloud-based, multi-user FEA pre-processing system, where multiple engineers can access and operate on the same model in a parallel environment. A prototype is discussed and tested, the results of which show that a multi-user preprocessor, where all computing is done on a central server that is hosted on a high performance system, provides significant benefits to the analysis team. These benefits include a shortened preprocessing time, and potentially higher-quality models.
An Investigation Into The Mechanisms Of Formation Of The Hard Zone In Fsw X65, Jacob D. Allred
An Investigation Into The Mechanisms Of Formation Of The Hard Zone In Fsw X65, Jacob D. Allred
Theses and Dissertations
Friction stir welding (FSW) of HSLA steel commonly produces a hard zone (HZ) on the advancing side (AS) of the weld. Despite its detrimental effects on weld toughness, the mechanisms of its formation have not been thoroughly investigated and are not well understood. This paper investigates the various mechanisms in FSW believed to affect the weld HZ, namely: strain, strain-rate, peak temperature and cooling rate. Gleeble tests indicate that strain and strain rate have negligible effects on weld HZ with cooling rate and peak temperature as dominant effects. Jominy tests resulted in cooling rate having 270% greater influence than peak …
Trajectory Generation And Optimization For Experimental Investigation Of Flapping Flight, Michael Schnebly Wilcox
Trajectory Generation And Optimization For Experimental Investigation Of Flapping Flight, Michael Schnebly Wilcox
Theses and Dissertations
Though still in relative infancy, the field of flapping flight has potential to have a far-reaching impact on human life. Nature presents a myriad of examples of successful uses of this locomotion. Human efforts in flapping flight have seen substantial improvement in recent times. Wing kinematics are a key aspect of this study. This study summarizes previous wing trajectory generators and presents a new trajectory generation method built upon previous methods. This includes a novel means of commanding unequal half-stroke durations subject to robotic trajectory continuity requirements. Additionally, previous optimization methods are improved upon. Experimental optimization is performed using the …
The Development Of Updated And Improved Slw Model Parameters And Its Application To Comprehensive Combustion Predictions, John T. Pearson
The Development Of Updated And Improved Slw Model Parameters And Its Application To Comprehensive Combustion Predictions, John T. Pearson
Theses and Dissertations
Accurate modeling of radiative heat transfer through combustion gases has received considerable attention in recent years. The spectral line weighted-sum-of-gray-gases (SLW) model was developed based on detailed line-by-line spectral data of gases. A critical element of the SLW model is the absorption line blackbody distribution function (ALBDF). This function was designed to utilize the spectral properties of gases in an efficient and compact manner. However, there are several limitations of the ALBDF in its original form. First, the valid ranges of temperature and pressure are not large enough to include important applications, such as oxy-combustion, where temperatures can exceed 2500 …
Application Of Machine Learning And Parametric Nurbs Geometry To Mode Shape Identification, Robert Mceuen Porter
Application Of Machine Learning And Parametric Nurbs Geometry To Mode Shape Identification, Robert Mceuen Porter
Theses and Dissertations
In any design, the dynamic characteristics of a part are dependent on its geometric and material properties. Identifying vibrational mode shapes within an iterative design process becomes difficult and time consuming due to frequently changing part definition. Although research has been done to improve the process, visual inspection of analysis results is still the current means of identifying each vibrational mode determined by a modal analysis. This research investigates the automation of the mode shape identification process through the use of parametric geometry and machine learning.In the developed method, displacement results from finite element modal analysis are used to create …
Design Exploration And Analysis Of Carbon-Infiltrated Carbon Nanotube Vascular Stents, Darrell John Skousen
Design Exploration And Analysis Of Carbon-Infiltrated Carbon Nanotube Vascular Stents, Darrell John Skousen
Theses and Dissertations
The purpose of this research was to design, develop, and test coronary stent designs composed of carbon-infiltrated carbon nanotubes (CI-CNTs). Coronary stents currently have two major complications: restenosis and thrombosis. CI-CNT stents have potential to address both of these issues, and therefore may provide improved clinical outcomes. CI-CNT stent geometry is patterned using high-resolution photolithography that provide advantages in design possibilities.To develop a coronary stent, a standard design process was followed including: background, design specifications, concept generation, development, analysis, and testing. Background research was first completed and general design specifications for coronary stent performance were compiled. Multiple design concepts were …
Origami-Based Design For Engineering Applications, Kevin Campbell Francis
Origami-Based Design For Engineering Applications, Kevin Campbell Francis
Theses and Dissertations
Origami can be a powerful source of design inspiration in the creation of reconfigurable systems with unparalleled performance. This thesis provides fundamental tools for designers to employ as origami-based designs are pursued in their respective fields of expertise. The first chapter introduces origami and makes connections between origami and engineering design through a survey of engineered applications and characterizing the relationship between origami and compliant mechanisms. The second chapter evaluates the creasing of non-paper sheet materials, such as plastics and metals, to facilitate origami-based compliant mechanism design. Although it is anticipated that most origami-based design will result from surrogate folds …
The Influence Of Superhydrophobicity On Laminar Jet Impingement And Turbulent Flow In A Channel With Walls Exhibiting Riblets, Joseph Fletcher Prince
The Influence Of Superhydrophobicity On Laminar Jet Impingement And Turbulent Flow In A Channel With Walls Exhibiting Riblets, Joseph Fletcher Prince
Theses and Dissertations
The object of this work is to explore the influence superhydrophobic (SH) surfaces exert in laminar jet impingement and when they are combined with riblets in turbulent channel flow. A SH surface generates an apparent slip due to the combination of micropatterning and chemical hydrophobicity. Because of surface tension, water does not enter the cavities between the features, increasing the contact angle of a water droplet on the surface and reducing the liquid-solid contact area. An analysis based on the integral momentum approach of Karman and Pohlhausen is presented that predicts jet impingement behavior on SH surfaces. The model is …
Thermal Transport To Sessile Water Droplets On Heated Superhydrophobic Surfaces Of Varying Cavity Fraction, Robb C. Hays
Thermal Transport To Sessile Water Droplets On Heated Superhydrophobic Surfaces Of Varying Cavity Fraction, Robb C. Hays
Theses and Dissertations
The hydrophobicity of a surface is defined as the degree to which it repels water molecules, and the internal contact angle that the droplet makes with the surface is a measure of the hydrophobicity. Contact angles less than 90° occur on hydrophilic surfaces, while contact angles greater than 90° occur on hydrophobic surfaces. If a surface's contact angle is greater than 120° the surface is commonly defined as superhydrophobic (SH). Superhydrophobicity is accomplished through a combination of microscale surface roughness and water repellant surface chemistry. The roughness creates cavities, or pockets, of vapor underneath the droplet which act to increase …
Particle Morphology And Elemental Composition Of Heavy Fuel Oil Ash At Varying Atomization Pressures, Daniel Abraham Tovar
Particle Morphology And Elemental Composition Of Heavy Fuel Oil Ash At Varying Atomization Pressures, Daniel Abraham Tovar
Theses and Dissertations
Land-based turbine engines are currently used to burn heavy fuel oil (HFO), which is a lower cost fuel. HFO contains inorganic material that forms deposits on turbine blades reducing output and efficiency. Magnesium based additives are used to inhibit vanadium pentoxide deposition and reduce the corrosive nature of the gas and deposits in the hot gas path of the gas turbine. The focus of this study was to determine particle morphology and elemental composition of ash when firing HFO in an atmospheric combustor at various fuel injector atomization pressures. Prior to firing, the HFO was washed with water to remove …
Vision-Based Guidance For Air-To-Air Tracking And Rendezvous Of Unmanned Aircraft Systems, Joseph Walter Nichols
Vision-Based Guidance For Air-To-Air Tracking And Rendezvous Of Unmanned Aircraft Systems, Joseph Walter Nichols
Theses and Dissertations
This dissertation develops the visual pursuit method for air-to-air tracking and rendezvous of unmanned aircraft systems. It also shows the development of vector-field and proportional-integral methods for controlling UAS flight in formation with other aircraft. The visual pursuit method is a nonlinear guidance method that uses vision-based line of sight angles as inputs to the algorithm that produces pitch rate, bank angle and airspeed commands for the autopilot to use in aircraft control. The method is shown to be convergent about the center of the camera image frame and to be stable in the sense of Lyapunov. In the lateral …
Development Of A Sense And Avoid System For Small Unmanned Aircraft Systems, Robert Andrew Klaus
Development Of A Sense And Avoid System For Small Unmanned Aircraft Systems, Robert Andrew Klaus
Theses and Dissertations
Unmanned aircraft systems (UAS) represent the future of modern aviation. Over the past 10 years their use abroad by the military has become commonplace for surveillance and combat. Unfortunately, their use at home has been far more restrictive. Due to safety and regulatory concerns, UAS are prohibited from flying in the National Airspace System without special authorization from the FAA. One main reason for this is the lack of an on-board pilot to "see and avoid" other air traffic and thereby maintain the safety of the skies. Development of a comparable capability, known as "Sense and Avoid" (SAA), has therefore …
Real-Time Visualization Of Finite Element Models Using Surrogate Modeling Methods, Ryan C. Heap
Real-Time Visualization Of Finite Element Models Using Surrogate Modeling Methods, Ryan C. Heap
Theses and Dissertations
Finite element analysis (FEA) software is used to obtain linear and non-linear solutions to one, two, and three-dimensional (3-D) geometric problems that will see a particular load and constraint case when put into service. Parametric FEA models are commonly used in iterative design processes in order to obtain an optimum model given a set of loads, constraints, objectives, and design parameters to vary. In some instances it is desirable for a designer to obtain some intuition about how changes in design parameters can affect the FEA solution of interest, before simply sending the model through the optimization loop. This could …
The Effect Of Cooling Rate Of Friction Stir Welded High Strength Low Alloy Steel, Scott Anthony Rose
The Effect Of Cooling Rate Of Friction Stir Welded High Strength Low Alloy Steel, Scott Anthony Rose
Theses and Dissertations
The friction stir welding of steel has produced a hard zone in several different alloys. Despite its detrimental effects on weld toughness, the reasons behind neither its formation nor a method of reducing its size or effects have been explored. Recent advances in process control allow for direct heat input control, which combined with the use of backing plates of different thermal conductivity allows for an expansion of the process window. These control methods also affect the HAZ cooling rate by providing greater range (a 60% increase compared to a fixed backing plate) and control (five welds within 16 °C/s). …
Popup Height And The Dynamics Of Rising Buoyant Spheres, Randy H. Munns
Popup Height And The Dynamics Of Rising Buoyant Spheres, Randy H. Munns
Theses and Dissertations
In this paper the popup height of rising buoyant spheres is studied over a range of distinct release depths along with the accompanying velocities and accelerations near the free surface. In the past, regimes of motion due to vortex induced vibrations have been classified based on trajectories below the free surface. This study focuses on the popup height, velocity and acceleration at free surface exit, and vortex shedding in order to further define regimes of motion experienced by a rising buoyant sphere. Varying the release depth below the free surface reveals varying exit angles, velocities, accelerations, and popup heights at …
A Comparative Analysis Of Energy Modelingmethods For Commercial Buildings, Spencer Mark Salmon
A Comparative Analysis Of Energy Modelingmethods For Commercial Buildings, Spencer Mark Salmon
Theses and Dissertations
This thesis researched the accuracy of measured energy data in comparison to estimated hand calculation data and estimated building energy performance simulation data. In the facility management industry, there is minimal evidence that building energy performance software is being used as a benchmark against measured energy usage within a building. Research was conducted to find examples of measured energy data compared to simulated data. The study examined the accuracy of a simulation software and hand calculations to measured energy data. Data suggests that comparisons may be made between building energy performance simulated data and measured data, though comparisons are solely …
Variable Fidelity Optimization With Hardware-In-The-Loop For Flapping Flight, Michael Luke Duffield
Variable Fidelity Optimization With Hardware-In-The-Loop For Flapping Flight, Michael Luke Duffield
Theses and Dissertations
Hardware-in-the-loop (HIL) modeling is a powerful way of modeling complicated systems. However, some hardware is expensive to use in terms of time or mechanical wear. In cases like these, optimizing using the hardware can be prohibitively expensive because of the number of calls to the hardware that are needed. Variable fidelity optimization can help overcome these problems. Variable fidelity optimization uses less expensive surrogates to optimize an expensive system while calling it fewer times. The surrogates are usually created from performing a design of experiments on the expensive model and fitting a surface to the results. However, some systems are …
The Sustainability Of Lean Manufacturing As A Competitive Advantage, Louis G. Jones
The Sustainability Of Lean Manufacturing As A Competitive Advantage, Louis G. Jones
Theses and Dissertations
Since the early 1990s lean manufacturing has been employed by companies looking to reduce costs, increase efficiencies and improve quality. Academic studies of the financial benefits of lean manufacturing are mixed in their results, where some show benefit and others do not. The objective of the current work was to confirm a financial benefit of lean manufacturing, while also establishing whether such a financial advantage was sustainable. Financial data was collected for a large number of companies in the manufacturing sector, over the period from 1990 to 2010. The data were used to show correlation between inventory turns and return …
The Water Entry Of Slender Axisymmetric Bodies: Forces, Trajectories And Acoustics, Kyle Gordon Bodily
The Water Entry Of Slender Axisymmetric Bodies: Forces, Trajectories And Acoustics, Kyle Gordon Bodily
Theses and Dissertations
Free surface water entry of various objects has been studied using high-speed images and image processing techniques for decades. This thesis studies the forces, velocities, and trajectories of slender axisymmetric projectiles using an embedded inertial measurement unit (IMU). Three nose shapes (cone, ogive, and flat) were used in the study. Additionally, the projectiles were tested at vertical and oblique impact angles with different surface conditions. One-half of each projectile was coated down the centerline with a hydrophobic spray, creating a half hydrophobic, half hydrophilic case. The trajectory of this half-and-half case impacting vertically was compared to the trajectory of symmetrically …
Dynamics And Control Of Wrist And Forearm Movements, Allan W. Peaden
Dynamics And Control Of Wrist And Forearm Movements, Allan W. Peaden
Theses and Dissertations
Wrist and forearm motion is governed both by its dynamics and the control strategies employed by the neuromuscular system to execute goal oriented movement. Two experiments were conducted to increase our understanding of wrist and forearm motion. The first experiment involved 10 healthy subjects executing planned movements to targets involving all three degrees of freedom (DOF) of the wrist and forearm, namely wrist flexion-extension (FE), wrist radial-ulnar deviation, and forearm pronation-supination (PS). A model of wrist and forearm dynamics was developed, and the recorded movements were fed into the model to analyze the movement torques. This resulted in the following …
A Study Of Action Origami As Systems Of Spherical Mechanisms, Landen A. Bowen
A Study Of Action Origami As Systems Of Spherical Mechanisms, Landen A. Bowen
Theses and Dissertations
Origami, the Japanese art of paper folding, has been used previously to inspire engineering solutions for compact, deployable designs. Action origami, the subset of origami dealing with models designed to move, is a previously unexplored area for engineering design solutions that are deployable and have additional motion in the deployed state. A literature review of origami in engineering is performed, resulting in seven key areas of technical origami literature from a wide variety of disciplines. Spherical mechanisms are identified as the method by which most action origami models achieve complicated motion while remaining flat-foldable. The subset of action origami whose …
Capillary Filling Of Large Aspect Ratio Channels With Varying Wall Spacing, Dallin B. Murray
Capillary Filling Of Large Aspect Ratio Channels With Varying Wall Spacing, Dallin B. Murray
Theses and Dissertations
Quantification and prediction of capillary fluid flow in planar nanochannels is essential to the development of many emerging nanofluidic technologies. Planar nanochannels are typically produced using the standard nanofabrication processes of thermal bonding or sacrificial etching. Both approaches may yield nanochannels that are bowed and/or exhibit non-uniform (i.e. non-planar) wall spacing. These variations in wall spacing affect the transient dynamics of a liquid plug filling the nanochannel, causing deviations from the classical behavior in a parallel-plate channel as described by the Washburn model. Non uniform wall spacing impacts the overall frictional resistance and influences the meniscus curvature. In this thesis, …
An Alternative System Identification Method For Friction Stir Processing, Dustin John Marshall
An Alternative System Identification Method For Friction Stir Processing, Dustin John Marshall
Theses and Dissertations
Temperature control has been implemented in friction stir processing and has demonstrated the ability to give improved process control. In order to have optimal control of the process, the parameters of the system to be controlled must be accurately identified. The system parameters change with tool geometry and materials, workpiece materials, and temperature. This thesis presents the use of the relay feedback test to determine the system parameters. The relay feedback test is easy to use and promotes system stability during its use. The results from the relay feedback test can be used to determine controller gains for a PID …
Fluid-Structure Interactions With Flexible And Rigid Bodies, David J. Daily
Fluid-Structure Interactions With Flexible And Rigid Bodies, David J. Daily
Theses and Dissertations
Fluid structure interactions occur to some extent in nearly every type of fluid flow. Understanding how structures interact with fluids and visa-versa is of vital importance in many engineering applications. The purpose of this research is to explore how fluids interact with flexible and rigid structures. A computational model was used to model the fluid structure interactions of vibrating synthetic vocal folds. The model simulated the coupling of the fluid and solid domains using a fluid-structure interface boundary condition. The fluid domain used a slightly compressible flow solver to allow for the possibility of acoustic coupling with the subglottal geometry …
A Multiobjective Optimization Method For Collaborative Products With Application To Engineering-Based Poverty Alleviation, Nicholas Scott Wasley
A Multiobjective Optimization Method For Collaborative Products With Application To Engineering-Based Poverty Alleviation, Nicholas Scott Wasley
Theses and Dissertations
Collaborative products are created by combining components from two or more products to result in a new product that performs previously unattainable tasks. The resulting reduction in cost, weight, and size of a set of products needed to perform a set of functions makes collaborative products useful in the developing world. In this thesis, multiobjective optimization is used to design a set of products for optimal individual and collaborative performance. This is introduced through a nine step method which simultaneously optimizes multiple products both individually and collaboratively. The method searches through multiple complex design spaces while dealing with various trade-offs …
A Mathematical Model For Quantifying System Evolvability Using Excess And Modularity, Morgan Wesley Parry Tackett
A Mathematical Model For Quantifying System Evolvability Using Excess And Modularity, Morgan Wesley Parry Tackett
Theses and Dissertations
An important factor in system longevity is service-phase evolvability, which is defined as the ability of a system to physically transform from one configuration to a more desirable configuration while in service. These transformations may or may not be known during the design process, and may or may not be reversible. A study of 210 engineered systems was performed and found that system excess and modularity allow a system to evolve while in service. Building on these observations, this thesis introduces mathematical relationships that map a system's excess and modularity to that system's ability to evolve. These relationships are derived …
Using Topology Optimization To Numerically Improve Barriers To Reverse Engineering, Devin Donald Lebaron
Using Topology Optimization To Numerically Improve Barriers To Reverse Engineering, Devin Donald Lebaron
Theses and Dissertations
Here explored is a method by which designers can use the tool of topology optimization to numerically improve barriers to reverse engineering. Recently developed metrics, which characterize the time (T) to reverse engineer a product, enable this optimization. A key parameter use din the calculation of T is information content (K). The method presented in this thesis pursues traditional topology optimization objectives while simultaneously maximizing K, and thus T, in the resulting topology. This thesis presents new algorithms to 1) evaluate K for any topology, 2)increase K for a topology by manipulating macro-scale geometry and micro-scale crystallographic information for each …
An Exploration Of Carbon-Filled Carbon Nanotubes As A Potential Material In Coronary Stents, Kristopher Neil Jones
An Exploration Of Carbon-Filled Carbon Nanotubes As A Potential Material In Coronary Stents, Kristopher Neil Jones
Theses and Dissertations
The purpose of this research is to explore the potential of using carbon-infiltrated carbon nanotubes (CI-CNT) as a material for coronary artery stents. Stents are commonly fabricated from metal, which may not perform as well as many polymers and ceramics in biomedical applications. Pyrolytic carbon, a ceramic, is currently used in medical implant devices due to its preferrable biocompatibility properties. Micro-patterned pyrolytic carbon devices can be created by growing carbon nanotubes, and then filling the space between with amorphous carbon via chemical vapor deposition. We prepared multiple samples of two different planar stent-like flexible geometries and smaller cubic structures out …
A Vision-Based Relative Navigation Approach For Autonomous Multirotor Aircraft, Robert C. Leishman
A Vision-Based Relative Navigation Approach For Autonomous Multirotor Aircraft, Robert C. Leishman
Theses and Dissertations
Autonomous flight in unstructured, confined, and unknown GPS-denied environments is a challenging problem. Solutions could be tremendously beneficial for scenarios that require information about areas that are difficult to access and that present a great amount of risk. The goal of this research is to develop a new framework that enables improved solutions to this problem and to validate the approach with experiments using a hardware prototype. In Chapter 2 we examine the consequences and practical aspects of using an improved dynamic model for multirotor state estimation, using only IMU measurements. The improved model correctly explains the measurements available from …