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Articles 31 - 60 of 234
Full-Text Articles in Mechanical Engineering
Mechanical Characterization Of Animal Derived Starting Materials For Tissue Engineering, Bin Zhang
Mechanical Characterization Of Animal Derived Starting Materials For Tissue Engineering, Bin Zhang
Dissertations
Animal derived starting materials are well established in the production of Tissue Engineered Medical Devices. Porcine specifically can be found in products ranging in application from hernia repair to breast reconstruction. Although this material has been largely accepted in the Tissue Engineering industry, little is known of its material properties and mechanical characteristics. A review of the scientific literature describes limited mechanical measures only on uncontrolled research grade material. The objective of this work is to mechanically characterize porcine starting material used in the medical device industry. Porcine skin is provided by Midwest Research Swine, LLC (MRS) an established supplier …
Evaporation Rate From Free Water Surface, Safa M. Aldarabseh
Evaporation Rate From Free Water Surface, Safa M. Aldarabseh
Dissertations
This work aims to perform an experiment in the laboratory and investigate the effect of the wave steepness, airflow velocity, air relative humidity, air temperature, and water surface temperature on the evaporation rate from still and wavy water surface. In this investigation, the experimental results are used to quantify an evaporation rate from a still and wavy water surface under different convection regimes that are free, mixed, and forced convection under turbulent airflow conditions. Empirical correlations are also derived using the experimental results based on modified Dalton’s law and Similarity method (analogy between mass and heat transfer equation). In this …
Team Creation Methods In Practice: Understanding The Potential Effects Of Nonverbal Communication In The Leadership Of Team Formation, Troy Allen Robertson
Team Creation Methods In Practice: Understanding The Potential Effects Of Nonverbal Communication In The Leadership Of Team Formation, Troy Allen Robertson
Dissertations
Teams require leadership, even if they are self-managed. The group of individuals who make up a team must be gathered in some form or another. For self managed teams to function successfully, the first step is the process of creating the team. Many aspects may factor into the creation process. Often time is of the essence and methods to quickly assess and form teams show merit. First impressions in general are based largely on nonverbal communication. The focus of this mixed-methods concurrent embedded study is to analyze the potential effects of nonverbal communication on influencing team creation. A group of …
A Reinforcement Learning Approach To Spacecraft Trajectory Optimization, Daniel S. Kolosa
A Reinforcement Learning Approach To Spacecraft Trajectory Optimization, Daniel S. Kolosa
Dissertations
This dissertation explores a novel method of solving low-thrust spacecraft targeting problems using reinforcement learning. A reinforcement learning algorithm based on Deep Deterministic Policy Gradients was developed to solve low-thrust trajectory optimization problems. The algorithm consists of two neural networks, an actor network and a critic network. The actor approximates a thrust magnitude given the current spacecraft state expressed as a set of orbital elements. The critic network evaluates the action taken by the actor based on the state and action taken. Three different types of trajectory problems were solved, a generalized orbit change maneuver, a semimajor axis change maneuver, …
Measurement Of Stresses And Their Effect On Transport In Thin Film Battery Electrodes, Subhajit Rakshit
Measurement Of Stresses And Their Effect On Transport In Thin Film Battery Electrodes, Subhajit Rakshit
Dissertations
At the moment, there is a significant push towards environmentally friendly energy production and gasoline-free transportation technologies. As a result, there is a renewed interest in energy storage devices such as lithium-ion batteries which will play a key role in providing energy storage capability for these applications. However, the current battery technology is reaching its limits and may not meet future energy storage demands. The increased demand and the limited lithium reserves in geographically remote areas of the earth will lead to higher cost of Li. The alternative battery technologies, such as sodium-ion batteries, are promising due to their low …
Development Of Heat Transfer Correlations For Low-Reynolds Numbers, Flows In Horizontal Circular Pipes, Latif Eyada Ibraheem
Development Of Heat Transfer Correlations For Low-Reynolds Numbers, Flows In Horizontal Circular Pipes, Latif Eyada Ibraheem
Dissertations
Turbulent flows are intrinsic to most fluid-based engineering systems, including internal combustion engines. In these devices, mixing, scalar transport and heat transfer are both critical for proper operation and challenging to model. In previous work, Kreun et al. [1] modeled a pre-heated intake manifold of a Diesel engine for cold-start simulations. Accurately predicting the heat transfer at the intake port proved to be a challenging task. Existing heat transfer correlations yielded predictions which were (at best) within 20% of the measured values. The discrepancy was attributed to a mismatch between the range of applicability of existing heat transfer models and …
Epitaxial Growth Of Iii-Nitride Nanostructures And Their Optoelectronic Applications, Moab Rajan Philip
Epitaxial Growth Of Iii-Nitride Nanostructures And Their Optoelectronic Applications, Moab Rajan Philip
Dissertations
Light-emitting diodes (LEDs) using III-nitride nanowire heterostructures have been intensively studied as promising candidates for future phosphor-free solid-state lighting and full-color displays. Compared to conventional GaN-based planar LEDs, III-nitride nanowire LEDs exhibit numerous advantages including greatly reduced dislocation densities, polarization fields, and quantum-confined Stark effect due to the effective lateral stress relaxation, promising high efficiency full-color LEDs. Beside these advantages, however, several factors have been identified as the limiting factors for further enhancing the nanowire LED quantum efficiency and light output power. Some of the most probable causes have been identified as due to the lack of carrier confinement in …
Experimental And Numerical Characterization Of Multiphase Subsurface Oil Release, Feng Gao
Experimental And Numerical Characterization Of Multiphase Subsurface Oil Release, Feng Gao
Dissertations
Subsurface oil release is commonly encountered in the natural environment and engineering applications and has received the substantial attention of researchers after the disastrous Deepwater Horizon Blowout oil spill in 2009. The main focus on the present research is to systematically study the hydrodynamics of underwater oil jet under a variety of conditions, including the effect of dispersant and different gas to oil ratios (GOR) by using experimental measurement as well as a Computational Fluid Dynamics (CFD) approach, from which the measured turbulent characteristics (e.g., velocity, turbulent kinetic energy, turbulence dissipation rate, etc.) of underwater oil jet are thoroughly examined …
Hybrid Processes In Material Removal Of Hard And Brittle Materials, Hossein Mohammadi
Hybrid Processes In Material Removal Of Hard And Brittle Materials, Hossein Mohammadi
Dissertations
New technologies demand new materials with better mechanical, optical, and thermal properties. Materials that are light weight, strong with high resistance to high temperatures, and compatible with a predetermined condition. Such materials usually are challenging to manufacture and process compared to widely available materials such as metals. Ceramics and semiconductors are considered extremely hard and brittle, making them very difficult to cut and manufacture. The other major and fast-growing type of materials are composites (including Ceramic Matrix Composites, CMC) that are also considered very challenging to machine. All these materials have many applications in major industries (i.e. electronics, aerospace, optics, …
Finite Element Modeling And Experimental Characterization Of Knot Configuration Effect On The Mechanical Performance Of Surgical Suture, Arz Y. Qwam Alden
Finite Element Modeling And Experimental Characterization Of Knot Configuration Effect On The Mechanical Performance Of Surgical Suture, Arz Y. Qwam Alden
Dissertations
Tendon injuries in orthopedic surgery and sports medicine are escalating; hence there is great interest in improving tendon repair. The integrity of tendon repair depends in part on a combination of suture material, suture size and knot configuration. Recent studies have indicated the failure of surgical knots as a failure mode during surgical repair. Further, there is still no consensus on the ideal (best/safest) surgical knot techniques. Also, this failure mode is related to stress concentrations, which cannot be easily established with traditional tensile testing. Most researchers have focused on the measurement and comparison of the gross structural response of …
Decomposition And Ionization Of Ionic Liquids, Forrest Grady Kidd Iii
Decomposition And Ionization Of Ionic Liquids, Forrest Grady Kidd Iii
Dissertations
The United States Air Force is interested in developing a situationally responsive space environment. In order to achieve this, dual-mode-propulsion will be utilized. A new class of propellants is being developed for this application based on energetic ionic liquids. Two ionic liquids of current interest are Hydroxylammonium Nitrate (HAN) and Hydroxyethylhydrazinium Nitrate (HEHN) due to their beneficial performance characteristics. The decomposition and ionization chemistry of these two species is investigated in this work. Using GAUSSIAN09 software, reactions with important radicals are explored through quantum chemistry. The energetics of reactions as well as the identity of key product complexes are given. …
Measurements Of Fluid Structures And Mass Transport In Channel With Fabric Base, Karl David Mcallister
Measurements Of Fluid Structures And Mass Transport In Channel With Fabric Base, Karl David Mcallister
Dissertations
This thesis studies the relationships between flow structures and mass transport (dye concentration) within a Poiseuelle water flow glass chamber using optical flow experimental techniques in turbulent conditions. Through optical flow methods, velocity, vorticity, kinetic energy, Reynolds stress and turbulent production metrics where determined by laser illuminated glass beads and Rhodamine 6G dye removing from three different fabric substrates for multiple horizontal planes and one vertical plane. From the dye intensity, mass concentration metrics were determined providing visualization of velocity and mass transport simultaneously along with kinetic energy, mass flux, and concentration fluctuations.
Experiments And Multi-Field Modeling Of Inelastic Soft Materials, Shuolun Wang
Experiments And Multi-Field Modeling Of Inelastic Soft Materials, Shuolun Wang
Dissertations
Soft dielectrics are electrically-insulating elastomeric materials, which are capable of large deformation and electrical polarization, and are used as smart transducers for converting between mechanical and electrical energy. While much theoretical and computational modeling effort has gone into describing the ideal, time-independent behavior of these materials, viscoelasticity is a crucial component of the observed mechanical response and hence has a significant effect on electromechanical actuation. This thesis reports on a constitutive theory and numerical modeling capability for dielectric viscoelastomers, able to describe electromechanical coupling, large- deformations, large-stretch chain-locking, and a time-dependent mechanical response. This approach is calibrated to the widely-used …
Kinetic Study Of Free Radical-Radical Reactions Of Combustion Importance At Elevated Pressures, Chao Yan
Kinetic Study Of Free Radical-Radical Reactions Of Combustion Importance At Elevated Pressures, Chao Yan
Dissertations
Combustion mechanisms consist of hundreds elementary reactions of free radicals and stable molecules. Radical-radical elementary reactions play important roles due to the high concentration in which free radicals are accumulated in combustion systems. Radical-radical reactions are typically multi-channel. Some of the channels might be of chain propagation or even chain branching nature, while other channels might be of chain termination nature. The relative importance of different channels is pressure dependent. Compared to radical-molecule reactions, radical-radical reactions are much less studied. This is due to the difficulties of well characterized quantitative production of radical species as well as due to the …
Microfluidic Biosensor With Functionalized Gold Nano Particles On Interdigitated Electrodes, Bharath Babu Nunna
Microfluidic Biosensor With Functionalized Gold Nano Particles On Interdigitated Electrodes, Bharath Babu Nunna
Dissertations
The integration of the microfluidics to the biosensor has growing demand with favorable conditions such as reduced processing time and low reagent consumption. The immuno biosensing with the microfluidic platform helped to make the electrochemical biosensing assays portable due to which this sensing mechanism can be easily implemented in point of care devices. The implementation of the biosensing in the microchannels significantly reduces the sample requirement form milli liter (mL) to micro liter (uL), and thus leads to low volume sample requirement during the sensing. The primary factors contributing to the microfluidic biosensors performance are probe immobilization, specific binding and …
Electric-Field Assisted Manipulation And Self-Assembly Of Particle Suspensions, Edison Chijioke Amah
Electric-Field Assisted Manipulation And Self-Assembly Of Particle Suspensions, Edison Chijioke Amah
Dissertations
The aim of this dissertation is to model the processes by which particles suspended in liquids and at liquid surfaces self-assemble when they are subjected to uniform and non-uniform electric fields. To understand the role of electric forces, three related problems were studied numerically and experimentally.
In the first problem, particles are assumed to be suspended inside a liquid and a nonuniform electric field is applied using electrodes mounted in the domain walls which causes positively polarized particles to collect in the regions where the electric field intensity is locally maximal and the negatively polarized particles collect in the regions …
Aerosol Transport By Coughing In A Depressurized And Air-Conditioned Chamber, Bo Zhang
Aerosol Transport By Coughing In A Depressurized And Air-Conditioned Chamber, Bo Zhang
Dissertations
Expiratory droplets from human coughing in an air-conditioned environment have always been considered to be potential carriers of pathogens, responsible for respiratory disease transmission. The air movement/circulation and ambient conditions such as pressure and temperature are all key factors of aerosol transport. To study the transmission of disease by human coughing in a depressurized air-conditioned chamber, there are many technical challenges, including the following: 1) the study of simulating human coughing; 2) the collection of aerosol generated by coughing; 3) the CFD simulation of coughing-induced aerosol transport in an air-conditioned chamber; 4) the validation of such a CFD simulation by …
Field Induced Assembly Of Particulate Systems, Kinnari Shah
Field Induced Assembly Of Particulate Systems, Kinnari Shah
Dissertations
The primary focus of the first part of this dissertation is to study the AC field-driven assembly of monodisperse silica and glass particles on liquid - liquid interface and forming a liquid film of uniform thickness having arrangement of particles on it. This liquid film with arrangement of regular particles can be converted into a solid film by curing top UV curable liquid. Here, electric field is used as a tool to facilitate AC field-driven assembly. The work describes the assembly of different size of regular particles and effective development of solid film.
It is also shown that particles of …
Study On The Dispersion Of Particles At A Fluid-Liquid Interface And Its Application In Hydrophilous Pollination, Naga Aditya Musunuri
Study On The Dispersion Of Particles At A Fluid-Liquid Interface And Its Application In Hydrophilous Pollination, Naga Aditya Musunuri
Dissertations
This dissertation work describes the physics of particle adsorption and the spontaneous dispersion of powders that occurs when they come in contact with a fluid-liquid interface and its application in hydrophilous pollination of Ruppia Maritima, an aquatic plant. The dispersion of particles can occur so quickly that it appears explosive, especially for small particles on the surface of mobile liquids like water. PIV (Particle Image Velocimetry) measurements show that the adsorption of a spherical particle at the interface causes an axisymmetric streaming flow about the vertical line passing through the particle center. The fluid directly below the particle rises upward, …
Fast Estimation Model Of Pressure-Temperature Response For Planning Focused Ultrasound Surgery, Tariq Mohammad Arif
Fast Estimation Model Of Pressure-Temperature Response For Planning Focused Ultrasound Surgery, Tariq Mohammad Arif
Dissertations
High Intensity Focused Ultrasound (HIFU) is becoming a widely accepted modality for extracorporeal non-invasive hyperthermia and surgical procedures. Since ultrasonic transducers need to operate in various challenging body locations, the arrangement of their array elements can be optimized to improve the capability of controlling focus intensity. In the first part of this dissertation, patterns of pressure field variations with several selected design variables (kerf, transducer element’s number and element’s width-height) are studied. These patterns indicate that there is a more suitable shape and arrangement of transducer elements in a specified area to achieve highest possible pressure. In order to obtain …
A Meta-Analysis Of Energy Savings From Lighting Programs In Michigan, Teryila Ephraim Amough
A Meta-Analysis Of Energy Savings From Lighting Programs In Michigan, Teryila Ephraim Amough
Dissertations
In order to fill the gap in aggregates savings, the challenges faced by electric utilities for the demand of lighting energy are addressed by lighting efficiency programs. The shrinking capacity and electrical grid reliability call for improved ways to evaluate energy saving programs with evaluation methods that are robust in determining the impact of lighting programs. This study employed meta-analysis as an evaluation method to determine energy savings, impact, emissions of greenhouse gases (GHG), pollutants, and health effects from lighting programs in Michigan. The findings of the study showed the programs impact in Hedges’ g of 0.36 for the overall …
Design And Validation Of An Electro-Hydraulic Pressure-Control Valve And Closed-Loop Controller, Jerry Boza
Design And Validation Of An Electro-Hydraulic Pressure-Control Valve And Closed-Loop Controller, Jerry Boza
Dissertations
Electro-hydraulic pressure-control valves are used in many applications, such as manufacturing equipment, agricultural machinery, and aircrafts to name a few. They are often used to actuate hydraulic clutches, such as those found in power shift transmissions. A traditional pressure-control valve with open-loop control algorithm is typically used in clutch applications. This scheme often results in inconsistent or undesirable system behavior due to the nature of open-loop control as well as the nonlinear system dynamics and uncertainties.
In this research two new electro-hydraulic pressure-control valves were designed in order to decouple the valve and control port (hydraulic) dynamics. This was achieved …
Studying The Optimum Design Of Automotive Thermoelectric Air Conditioning, Alaa Attar
Studying The Optimum Design Of Automotive Thermoelectric Air Conditioning, Alaa Attar
Dissertations
The remarkable amount of research being conducted on thermoelectrics gives the impression that this technology will have a bright future in power generation and temperature control systems. At the present time, thermoelectrics is applied widely for temperature control, but has not yet replaced conventional air-conditioning systems due to its lower performance. Currently, approximately 10% of annual vehicle fuel consumption corresponds to the air-conditioning system used to cool the vehicle cabin. Conventional air-conditioning systems cool the entire cabin; however, about 73% of a vehicle’s mileage occurs while the driver is the only occupant. These facts indicate the need for a single …
On The Selection Of A Good Shape Parameter For Rbf Approximation And Its Application For Solving Pdes, Lei-Hsin Kuo
On The Selection Of A Good Shape Parameter For Rbf Approximation And Its Application For Solving Pdes, Lei-Hsin Kuo
Dissertations
Meshless methods utilizing Radial Basis Functions~(RBFs) are a numerical method that require no mesh connections within the computational domain. They are useful for solving numerous real-world engineering problems. Over the past decades, after the 1970s, several RBFs have been developed and successfully applied to recover unknown functions and to solve Partial Differential Equations (PDEs).
However, some RBFs, such as Multiquadratic (MQ), Gaussian (GA), and Matern functions, contain a free variable, the shape parameter, c. Because c exerts a strong influence on the accuracy of numerical solutions, much effort has been devoted to developing methods for determining shape parameters which provide …
Analysis Of Vibroacoustic Properties Of Dimpled Beams Using A Boundary Value Model, Kyle R. Myers
Analysis Of Vibroacoustic Properties Of Dimpled Beams Using A Boundary Value Model, Kyle R. Myers
Dissertations
Attention has been given recently to the use of dimples as a means of passively altering the vibroacoustic properties of structures. Because of their geometric complexity, previous studies have modeled dimpled structures using the finite element method. However, the dynamics of dimpled structures are not completely understood. The goal of this study is to provide a better understanding of these structures through the development of a boundary value model (BVM) using Hamilton's Variational Principle. The focus of this study is on dimpled beams, which represent the simplest form of a dimpled structure.
A general model of a beam with N …
Modeling Of Environmentally Assisted Fatigue Crack Growth Behavior, Sree Phani Chandar Reddy
Modeling Of Environmentally Assisted Fatigue Crack Growth Behavior, Sree Phani Chandar Reddy
Dissertations
The formation of fatigue cracks and their propagation due to cyclic loading in metals have been a concern for more than hundred years. Since fatigue failure were first reported by the railroad industry in 1840s, tremendous progress has been achieved in understanding fatigue behavior of metals. But fatigue damage is still a concern due to its complex dependency on various environmental variable like humidity, temperature, time and corrosive environment. Although numerous theories and models have been proposed in the past, the effects of environment on fatigue crack growth (FCG) is not completely understood. This dissertation aims to shed light on …
Transient Cardiovascular Hemodynamics In A Patient-Specific Arterial System, Jr Rodward Hewlin
Transient Cardiovascular Hemodynamics In A Patient-Specific Arterial System, Jr Rodward Hewlin
Dissertations
The ultimate goal of the present study is to aid in the development of tools to assist in the treatment of cardiovascular disease. Gaining an understanding of hemodynamic parameters for medical implants allow clinicians to have some patient-specific proposals for intervention planning. In the present study a full cardiovascular experimental phantom and digital phantom (CFD model) was fabricated to study: (1) the effects of local hemodynamics on global hemodynamics, (2) the effects of transition from bed-rest to upright position, and (3) transport of dye (drug delivery) in the arterial system. Computational three dimensional (3-D) models (designs A, B, and C) …
Adaptive Control For Autonomous Navigation Of Mobile Robots Considering Time Delay And Uncertainty, Stephen Kofi Armah
Adaptive Control For Autonomous Navigation Of Mobile Robots Considering Time Delay And Uncertainty, Stephen Kofi Armah
Dissertations
Autonomous control of mobile robots has attracted considerable attention of researchers in the areas of robotics and autonomous systems during the past decades. One of the goals in the field of mobile robotics is development of platforms that robustly operate in given, partially unknown, or unpredictable environments and offer desired services to humans. Autonomous mobile robots need to be equipped with effective, robust and/or adaptive, navigation control systems. In spite of enormous reported work on autonomous navigation control systems for mobile robots, achieving the goal above is still an open problem. Robustness and reliability of the controlled system can always …
Development And Applications Of The Expanded Equivalent Fluid Method, Bharath Kumar Kandula
Development And Applications Of The Expanded Equivalent Fluid Method, Bharath Kumar Kandula
Dissertations
Ocean acoustics is the study of sound in the oceans. Electromagnetic waves attenuate rapidly in the water medium. Sound is the best means to transmit information underwater. Computational numerical simulations play an important role in ocean acoustics. Simulations of acoustic propagation in the oceans are challenging due to the complexities involved in the ocean environment. Different methods have been developed to simulate underwater sound propagation. The Parabolic-Equation (PE) method is the best choice in several ocean acoustic problems. In shallow water acoustic experiments, sound loses some of its energy when it interacts with the bottom. An equivalent fluid technique was …
Pbs Quantum Dot-Based Hetrojunction Solar Cells, Sawsan Khader Dagher
Pbs Quantum Dot-Based Hetrojunction Solar Cells, Sawsan Khader Dagher
Dissertations
This study investigates the influence of nanoparticles (NPs) size on their optical properties, and the effect of combination of lead sulfide (PbS) quantum dots (QDs), with n-type and p-type NPs, on the photogenerated charge carriers transport across the heterojunction solar cell structure. PbS QDs, of a range of sizes, were synthesized using a co-precipitation process. In this study, p-type NPs, which are poly [3,4-ethylenedioxythiophene] –poly [styrenesulfonate] (PEDOT: PSS), copper oxide (CuO) and graphene oxide (GO); and n-type NPs which are zinc oxide (ZnO), titanium dioxide (TiO2), cadmium sulfide (CdS) and bismuth sulfide (Bi2S3), were synthesized and characterized by SEM and …