Analysis Of Laser Induced Spallation Of Electron Beam Physical Vapor Deposited (Eb-Pvd) Thermal Barrier Coatings,
2013
Wright State University
Analysis Of Laser Induced Spallation Of Electron Beam Physical Vapor Deposited (Eb-Pvd) Thermal Barrier Coatings, David Allen Beeler
Browse all Theses and Dissertations
The use of thermal barrier coatings (TBCs) has been an important factor in the efficiency improvements of jet engines due to their ability to withstand the extreme environments within the engine. With this improved resistance, TBCs have also become more difficult to remove without damaging the substrate. Mound Laser & Photonics Center, Inc. (MLPC) has developed an innovative, laser based technique to spall this coating. The intention of this work was to investigate and better understand the removal mechanism. Through experimentation and analysis (such as high speed video, Scanning Electron Microscopy and Energy Dispersive Spectroscopy, semi-logarithmic analysis, and a numerical …
Structure And Properties Of Cocoons And Silk Fibers
Produced By Attacus Atlas,
2013
University of Nebraska - Lincoln
Structure And Properties Of Cocoons And Silk Fibers Produced By Attacus Atlas, Narendra Reddy, Yi Zhao, Yiqi Yang
Department of Textiles, Merchandising and Fashion Design: Faculty Publications
Silk fibers in the three layers of Attacus atlas (A. atlas) cocoons have morphological structure and tensile properties similar to that of Bombyx mori silk. Attempts are being made to produce silk for commercial applications from cocoons of relatively unknown wild insects due to the unique properties of the fibers and as a source of income and employment. In this research, A. atlas cocoons were used to study the chemical composition, morphology, physical structure and tensile properties of the silk fibers in the cocoons and ability of the fibers to support the attachment and proliferation of mouse fibroblast cells. It …
A Mathematical Evaluation Of Hemodynamic Parameters After Carotid Eversion And Conventional Patch Angioplasty,
2013
University of Nebraska Medical Center
A Mathematical Evaluation Of Hemodynamic Parameters After Carotid Eversion And Conventional Patch Angioplasty, Alexey Kamenskiy, Iraklis I. Pipinos, Yuris A. Dzenis, Prateek K. Gupta, Syed A. Jaffar Kazmi, Jason N. Mactaggart
Department of Mechanical and Materials Engineering: Faculty Publications
Carotid endarterectomy has a long history in stroke prevention, yet controversy remains concerning optimal techniques. Two methods frequently used are endarterectomy with patch angioplasty (CEAP) and eversion endarterectomy (CEE). The objective of this study was to compare hemodynamics-related stress and strain distributions between arteries repaired using CEAP and CEE. Mathematical models were based on in vivo three-dimensional arterial geometry, pulsatile velocity profiles, and intraluminal pressure inputs obtained from 16 patients with carotid artery disease. These data were combined with experimentally derived nonlinear, anisotropic carotid artery mechanical properties to create fluid-structure interaction models of CEAP and CEE. These models were then …
Effects Of Mode Coupling On The Admittance Of An At-Cut Quartz Thickness-Shear Resonator,
2013
University of Nebraska-Lincoln
Effects Of Mode Coupling On The Admittance Of An At-Cut Quartz Thickness-Shear Resonator, Huijing He, Jiashi Yang, Wei-Ping Zhang, Ji Wang
Department of Mechanical and Materials Engineering: Faculty Publications
We study the effects of couplings to flexure and face-shear modes on the admittance of an AT-cut quartz plate thickness-shear mode resonator. Mindlin’s two-dimensional equations for piezoelectric plates are employed. Electrically forced vibration solutions are obtained for three cases: pure thickness-shear mode alone; two coupled modes of thickness shear and flexure; and three coupled modes of thickness shear, flexure, and face shear. Admittance is calculated and its dependence on the driving frequency and the length/thickness ratio of the resonator is examined. Results show that near the thickness-shear resonance, admittance assumes maxima, and that for certain values of the length/thickness ratio, …
Analysis Of Electrically-Forced Vibrations Of Piezoelectric Mesa Resonators,
2013
University of Nebraska-Lincoln
Analysis Of Electrically-Forced Vibrations Of Piezoelectric Mesa Resonators, Huijing He, Guo-Quan Nie, Jin-Xi Liu, Jiashi Yang
Department of Mechanical and Materials Engineering: Faculty Publications
We study the electrically forced thickness-shear and thickness-twist vibrations of stepped thickness piezoelectric plate mesa resonators made of polarized ceramics or 6-mm class crystals. A theoretical analysis based on the theory of piezoelectricity is performed, and an analytical solution is obtained using the trigonometric series. The electrical admittance, resonant frequencies, and mode shapes are calculated, and strong energy trapping of the modes is observed. Their dependence on the geometric parameters of the resonator is also examined.
Wire Electro-Discharge Machining Of Titanium Alloy,
2013
University of Nebraska-Lincoln
Wire Electro-Discharge Machining Of Titanium Alloy, Farnaz Nourbakhsh, Kamlakar P. Rajurkar, Ajay P. Malshe, Jian Cao
Department of Mechanical and Materials Engineering: Faculty Publications
This paper presents an experimental investigation of wire electro-discharge machining (WEDM) of titanium alloy. The objective is to investigate the effect of seven process parameters including pulse width, servo reference voltage, pulse current, and wire tension on process performance parameters (such as cutting speed, wire rupture and surface integrity). A Taguchi L18 design of experiment (DOE) has been applied. All experiments have been conducted using Charmilles WEDM. It was also found that the cutting speed increases with peak current and pulse interval. Surface roughness was found to increase with pulse width and decrease with pulse interval. The Analysis of Variance …
Photovoltaic Device,
2013
Lincoln, NE
Photovoltaic Device, Jinsong Huang, Bin Yang, Yongbo Yuan
Department of Mechanical and Materials Engineering: Faculty Publications
An apparatus includes a substrate; and a photoactive layer disposed on the substrate. The photoactive layer includes an electron acceptor material; an electron donor material; and a material having dipoles.
A Comparative Study Of The Dry And Wet Nano-Scale Electro-Machining,
2013
Western Kentucky University
A Comparative Study Of The Dry And Wet Nano-Scale Electro-Machining, M. P. Jahan, K. R. Virwani, Kamlakar P. Rajurkar, A. P. Malshe
Department of Mechanical and Materials Engineering: Faculty Publications
In recent years, a nano-electromachining (nano-EM) process based on a scanning tunneling microscope (STM) platform has been demonstrated. Nano-EM is capable of machining nano-features, under both, liquid dielectric (wet nano-EM) and air dielectric (dry nano-EM) media. The objective of this paper is to present a comparative study between the wet and dry nano-EM processes based on process mechanism, machining performance, consistency and dimensional repeatability of these two processes. The comparison of the two processes has been conducted at near field nano-EM, where the gap between the tool electrode and workpiece is 2 nm and the machining is performed at room …
Inducing Neurite Outgrowth By Mechanical Cell Stretch,
2013
University of Nebraska-Lincoln
Inducing Neurite Outgrowth By Mechanical Cell Stretch, Suzanne Higgins, Jeong Soon Lee, Ligyeom Ha, Jung Yul Lim
Department of Mechanical and Materials Engineering: Faculty Publications
Establishing extracellular milieus to stimulate neuronal regeneration is a critical need in neuronal tissue engineering. Many studies have used a soluble factor (such as nerve growth factor or retinoic acid [RA]), micropatterned substrate, and electrical stimulation to induce enhanced neurogenesis in neuronal precursor cells. However, little attention has been paid to mechanical stimulation because neuronal cells are not generally recognized as being mechanically functional, a characteristic of mechanoresponsive cells such as osteoblasts, chondrocytes, and muscle cells. In this study, we performed proof-of-concept experiments to demonstrate the potential anabolic effects of mechanical stretch to enhance cellular neurogenesis. We cultured human neuroblastoma …
Systems Biology Of The Functional And Dysfunctional Endothelium,
2013
Imperial College London
Systems Biology Of The Functional And Dysfunctional Endothelium, Jennifer Frueh, Nataly Maimari, Takayuki Homma, Sandra M. Bovens, Ryan M. Pedrigi, Leila Towhidi, Rob Krams
Department of Mechanical and Materials Engineering: Faculty Publications
This review provides an overview of the effect of blood flow on endothelial cell (EC) signalling pathways, applying microarray technologies to cultured cells, and in vivo studies of normal and atherosclerotic animals. It is found that in cultured ECs, 5–10% of genes are up- or down-regulated in response to fluid flow, whereas only 3–6% of genes are regulated by varying levels of fluid flow. Of all genes, 90%are regulated by the steady part of fluid flow and 10% by pulsatile components. The associated gene profiles show high variability from experiment to experiment depending on experimental conditions, and importantly, the bioinformatical …
Elastic–Plastic Analysis And Strength Evaluation Of Adhesive
Joints In Wind Turbine Blades,
2013
University of Nebraska–Lincoln
Elastic–Plastic Analysis And Strength Evaluation Of Adhesive Joints In Wind Turbine Blades, Yi Hua, Ananth Ram Mahanth Kasavajhala, Linxia Gu
Department of Mechanical and Materials Engineering: Faculty Publications
The objective of this paper is to investigate the performance of adhesive joints of carbon/epoxy wind turbine blade subjected to combined bending and tension loadings through finite element method. The influence of adhesive material properties and geometrical details including fillet and imperfections was examined in terms of interlaminar stresses in the adhesive layer. The variation of stress intensity with change in adhesive shear modulus has also been investigated, while contour integral method was used for evaluating the stress intensity factors (SIF) at the imperfection tip. Furthermore, the strength of the joint was assessed through the crack initiation and propagation analysis. …
Structural, Optical And Electrical Properties Of Yttrium-Doped Hafnium Oxide Nanocrystalline Thin Films,
2013
University of Texas at El Paso
Structural, Optical And Electrical Properties Of Yttrium-Doped Hafnium Oxide Nanocrystalline Thin Films, Abhilash Kongu
Open Access Theses & Dissertations
Hafnium oxide (HfO2) has emerged as the most promising high-k dielectric for Metal-Oxide-Semiconductor (MOS) devices and has been highlighted as the most suitable dielectric materials to replace silicon oxide because of its comprehensive performance. In the present research, yttrium-doped HfO2 (YDH) thin films were fabricated using RF magnetron sputter deposition onto Si (100) and quartz with a variable thickness. Cross-sectional scanning electron microscopy coupled with Filmetrics revealed that film thickness values range from 700 A° to 7500 A°. Electrical properties such as AC Resistivity and current-voltage (I-V) characteristics of YDH films were studied. YDH films that were relatively thin (<1500 A°) crystallized in monoclinic phase while thicker films crystallized in cubic phase. The band gap (Eg) of the films was calculated from the optical measurements. The band gap was found to be ∼5.60 eV for monoclinic while it is ∼6.05 eV for cubic phase of YDH films. Frequency dependence of the electrical resistivity (ρac) and the total conductivity of the films were measured. Resistivity decreased (by three orders of magnitude) with increasing frequency from 100 Hz to 1 MHz, attributed due to the hopping mechanism in YDH films. Whereas, while ρac∼1Ω-m at low frequencies (100 Hz), it decreased to ∼ 104 Ω-cm at higher frequencies (1 MHz). Aluminum (Al) metal electrodes were deposited to fabricate a thin film capacitor with YDH layer as dielectric film thereby employing Al-YDH-Si capacitor structure. The results indicate that the capacitance of the films decrease with increasing film thickness. A detailed analysis of the electrical characteristics of YDH films is presented.
Experimental Comparison Study Of The Response Of Polycarbonate And Laminated Glass Blast Resistant Glazing Systems To Blast Loading,
2013
University of Kentucky
Experimental Comparison Study Of The Response Of Polycarbonate And Laminated Glass Blast Resistant Glazing Systems To Blast Loading, Joshua Calnan
Theses and Dissertations--Mining Engineering
This thesis recounts the experimental study of the dynamic response of polycarbonate blast resistant glazing systems to explosive loading through the use of triaxial load cells, pressure sensors, and a laser displacement gauge. This instrumentation captured the response of the glazing systems to blast loading over three phases of testing. The first phase of testing characterizes the load distribution around the perimeter and the second phase examines the repeatability of the results. The final phase of testing pushes the samples to failure. The results are then compared to HazL, a commonly used blast resistant glazing system analysis software tool. The …
Geodatabase-Assisted Storm Surge Modeling,
2013
Louisiana State University and Agricultural and Mechanical College
Geodatabase-Assisted Storm Surge Modeling, Sait Ahmet Binselam
LSU Doctoral Dissertations
Tropical cyclone-generated storm surge frequently causes catastrophic damage in communities along the Gulf of Mexico. The prediction of landfalling or hypothetical storm surge magnitudes in U.S. Gulf Coast regions remains problematic, in part, because of the dearth of historic event parameter data, including accurate records of storm surge magnitude (elevation) at locations along the coast from hurricanes. While detailed historical records exist that describe hurricane tracks, these data have rarely been correlated with the resulting storm surge, limiting our ability to make statistical inferences, which are needed to fully understand the vulnerability of the U.S. Gulf Coast to hurricane-induced storm …
Resolving Pronominal Anaphora Using Commonsense Knowledge,
2013
Louisiana State University and Agricultural and Mechanical College
Resolving Pronominal Anaphora Using Commonsense Knowledge, Seyedeh Leili Javadpour
LSU Doctoral Dissertations
Coreference resolution is the task of resolving all expressions in a text that refer to the same entity. Such expressions are often used in writing and speech as shortcuts to avoid repetition. The most frequent form of coreference is the anaphor. To resolve anaphora not only grammatical and syntactical strategies are required, but also semantic approaches should be taken into consideration. This dissertation presents a framework for automatically resolving pronominal anaphora by integrating recent findings from the field of linguistics with new semantic features. Commonsense knowledge is the routine knowledge people have of the everyday world. Because such knowledge is …
Designing A Cost Effective Microalgae Harvesting Strategy For Biodiesel Production With Electrocoagulation And Dissolved Air Flotation,
2013
Louisiana State University and Agricultural and Mechanical College
Designing A Cost Effective Microalgae Harvesting Strategy For Biodiesel Production With Electrocoagulation And Dissolved Air Flotation, Adam James Dassey
LSU Doctoral Dissertations
Microalgal harvesting strategies for biodiesel production have been a major setback in the industry with high energy estimates of $3400/ton biomass by centrifugation. The present study utilized effective mass and energy balances to reduce these large operating costs. The energy for Stage 1 centrifugation was reduced by 82% when harvesting 28.5% of biomass at 18 L/min as opposed to 95% harvesting at 1 L/min. This strategy was further confirmed using electrocoagulation (EC) with Nannochloris and Dunaliella algae with perforated aluminum and iron electrodes at low (< 6 mg/L) metal ion concentrations. Despite 20% lower harvesting efficiencies, the iron electrodes were more energy and cost efficient with operating costs less than $0.03/L oil when flocculating and settling Nannochloris and Dunaliella cultures. Furthermore, a continuous multistage algae harvester using EC and dissolved air flotation (DAF) for Stage 1 harvesting and centrifugation for Stage 2 dewatering was designed. It was determined throughout the testing that greater EC costs for improved harvesting efficiencies were necessary to offset the large energy requirements of the DAF. The multistage system dewatered a low density (100 mg/L) Nannochloris to 20% solids for a final energy requirement of 1.536 kWh/kg algae ($138/ton). Using the data collected from this research and existing literature, a life cycle analysis was assembled to judge the sustainability of microalgal biofuels in Louisiana. High and low energy estimates for culturing (mixing, CO2, nutrients), harvesting, lipid extraction and energy conversion were compared with the current research. Scaling the EC/DAF system for a full size facility was expected to reduce the harvesting costs to 1.133 kWh/kg algae, resulting as $0.44/L oil for a culture with 20% lipids. Despite this improvement in harvesting costs, the production of algal for the sole purpose of biodiesel was not economically viable. Considering a system with a growth rate of 15 g/m2/day and lipid content of 20%, the energy inputs exceeded the outputs from biodiesel production by 36% under the most ideal conditions. However, incorporating additional revenue through wastewater treatment and biogas production from residual biomass could improve sustainability and profitability of algal biodiesel to an 18.5% energy surplus at its current state.
Non-Equilibrium Pressure Control Of The Height Of A Large-Scale, Ground-Coupled, Rotating Fluid Column,
2013
Old Dominion University
Non-Equilibrium Pressure Control Of The Height Of A Large-Scale, Ground-Coupled, Rotating Fluid Column, R. L. Ash, I. R. Zardadhkan
Mechanical & Aerospace Engineering Faculty Publications
When a ground-coupled, rotating fluid column is modeled incorporating non-equilibrium pressure forces in the Navier-Stokes equations, a new exact solution results. The solution has been obtained in a similar manner to the classical equilibrium solution. Unlike the infinite-height, classical solution, the non-equilibrium pressure solution yields a ground-coupled rotating fluid column of finite height. A viscous, non-equilibrium Rankine vortex velocity distribution, developed previously, was used to demonstrate how the viscous and non-equilibrium pressure gradient forces, arising in the vicinity of the velocity gradient discontinuity that is present in the classical Rankine vortex model, effectively isolate the rotating central fluid column from …
Microstructure And Mechanical Properties Of Titanium Nitride Optical Coatings Made By Dc Magnetron Sputtering,
2013
University of Texas at El Paso
Microstructure And Mechanical Properties Of Titanium Nitride Optical Coatings Made By Dc Magnetron Sputtering, Gustavo Martinez
Open Access Theses & Dissertations
Titanium nitride (TiNx) thin films were grown by DC (Direct Current) magnetron sputtering method onto Si(100) substrates by varying time of deposition to produce films with variable thickness (dTiN) in the range of 20-120 nm. The grown TiNx films were characterized by studying their structure, composition, and mechanical properties. Nuclear reaction analysis (NRA) combined with Rutherford backscattering spectrometry (RBS) analyses indicate that the grown films were stoichiometric TiN. Grazing incidence X-ray diffraction (GIXRD) measurements indicate that the texturing of the TiN films changes as a function of dTiN. The (111) and (002) peaks appear initially; with increasing dTiN, (111) becomes …
Structure And Electronic Properties Of Pure And Nitrogen Doped Nanocrystalline Tungsten Oxide Thin Films,
2013
University of Texas at El Paso
Structure And Electronic Properties Of Pure And Nitrogen Doped Nanocrystalline Tungsten Oxide Thin Films, Vemnkata Rama Sesha Ravi Kumar Vemuri
Open Access Theses & Dissertations
Tungsten oxide (WO3) is a multifunctional material which has applications in electronics, sensors, optoelectronics, and energy-related technologies. Recently, electronic structure modification of WO3 to design novel photocatalysts has garnered significant attention. However, a fundamental understanding of nitrogen induced changes in the structure, morphology, surface/interface chemistry, and electronic properties of WO3 is a prerequisite to producing materials with the desired functionality and performance. Also, understanding the effect of thermodynamic and processing variables is highly desirable in order to derive the structure-property relationships in the W-O/W-O-N material system. The present work was, therefore, focused on studying the effects …
Automated Semantic Content Extraction From Images,
2013
Louisiana State University and Agricultural and Mechanical College
Automated Semantic Content Extraction From Images, Mahdi Arab Khazaeli
LSU Doctoral Dissertations
In this study, an automatic semantic segmentation and object recognition methodology is implemented which bridges the semantic gap between low level features of image content and high level conceptual meaning. Semantically understanding an image is essential in modeling autonomous robots, targeting customers in marketing or reverse engineering of building information modeling in the construction industry. To achieve an understanding of a room from a single image we proposed a new object recognition framework which has four major components: segmentation, scene detection, conceptual cueing and object recognition. The new segmentation methodology developed in this research extends Felzenswalb's cost function to include …
