Engineering Commons^™

Comparative Properties Of Polymers Guiding The Development Of An Abdominal Aorta Model, Benjamin Michael Lamie

Masters Theses

Hemodynamics, the study of the forces involved in the circulation of blood, is an area that researchers have approached in various manners for many years. The study of how blood flows through arteries and veins as well as the effect of the composition of the blood has been defined and thoroughly characterized in past studies. Although in-depth studies have been performed on the flow characteristics of blood, most often the observations are made as the fluid flows through tubes composed of some rigid material. It is well known that the arteries and veins have a layered histology that show varying …

A Study Of Material Properties And Relevant Microstructure Parameters That May Influence The V50 Ballistic Limit Velocity Of Composite Ceramics, Adolphus Mcdonald

Masters Theses

The purpose of this research is to evaluate, compare, and correlate the microstructure and mechanical properties of a selected group of ceramic armor samples to the V₅₀ ballistic limit velocity. This study is to identify any relation between the desired material properties and the relevant microstructure parameters that significantly influence the ballistic limit velocity. The ceramic materials, silicon carbide and boron carbide, were produced and provided by five foreign companies. These companies were under contract by the United States Army, Research, Development, and Engineering Command to provide ceramic armor for comparative testing and material evaluation.

Ballistic testing was carried …

A Computational Model To Predict In Vivo Kinetics In Implanted And Non-Implanted Shoulders, Matthew Brennon-Kyle Kubo

Masters Theses

The purpose of this study was to develop and implement a computational model designed to input in vivo kinematic and predict in vivo forces and torques for the shoulder, elbow, and wrist in normal, rotator cuff-deficient (RCD), reverse shoulder arthroplasty (RSA) and total shoulder arthroplasty (TSA) shoulder subjects. Twenty subjects, divided evenly amongst the four shoulder types, performed a box-lift activity while under fluoroscopic surveillance. Three dimensional (3D) in vivo kinematics was determined for the subjects using implant models and bone models created from CT (computed tomography) scans in a 2D-to-3D registration process. The kinematics were used as input for …

Real-Time Monitoring And Quantification Of Drug Induced Changes In Endothelial Cytoskeleton Filaments Using A Cellular Impedance Biosensor, Vijay Nandakumar

Masters Theses

The analysis of electrical signals originating from biological cells and tissues have yielded a large amount of useful information over the past years. Technologies have been developed, wherein we can monitor the health of the biological material of interest using these electrical signals. Instruments for the study of living cells have historically been of significant importance for such things as basic neuroscience, cell biology, pharmaceutical screening, environmental monitoring, and toxin detection. One of the practical realizations of these methods was successfully implemented by Giaver and Keese with their Electric Cell-Substrate Impedance Sensing (ECIS) system. The purpose of this Masters Thesis …

Determination And Comparison Of In Vivo Forces And Torques In Normal And Degenerative Lumbar Spines, Shaun Kevin Stinton

Masters Theses

In vivo motions of normal and degenerative lumbar spine patients performing extension/flexion were obtained using video fluoroscopy. 3-D models of each patient’s vertebrae were registered to the 2-D fluoroscopy images using a process developed at Rocky Mountain Musculoskeletal Research Laboratory. Temporal equations representing the motions were input into a math model and the forces at the contact point between vertebral levels and the body torques between the vertebrae were the output. The vertical forces in the normal and degenerative patients were similar and ranged from 0.35-0.42 times the body weight of the patient. The maximum torques were higher in the …

Correlation Of Wear And Mechanics For Subjects Having A Metal-On-Polyethylene Total Hip Arthroplasty Measured In Vivo, Katherine Suzanne Alford

Masters Theses

Femoral head separation from the acetabular shell has been recorded, but clinical significance of this phenomenon has not yet been established. The objective of the study was to determine if there is a correlation between femoral head separation (sliding of the femoral head away from the acetabular cup), hip joint forces, and acetabular liner wear. Twenty subjects were strategically selected to participate in this study. All subjects were asked to perform gait on a treadmill while under fluoroscopic surveillance. The number of incidences involving femoral head separation was tallied and acetabular bearing surface forces were determined for each subject. A …

Study Of Secondary Electron Emission From Niobium At Cryogenic Temperatures, Anoop George

UNLV Theses, Dissertations, Professional Papers, and Capstones

The objective of this project is to study the properties of secondary electron emission from niobium samples, cleaned at the Los Alamos National Laboratory, at cryogenic temperatures to enhance existing multipacting codes with data on the samples. The predominant cause of power loss in radio-frequency superconducting accelerators cavities is multipacting. This project studies the secondary electron distribution from niobium metal due to incident primary electrons. The experiments on the niobium sample are performed in an environment close to that present in a superconducting accelerator cavity.

The experiment is performed in a vacuum chamber capable of achieving ultra high vacuum levels …

Mechanical Behavior Of Cracked Panels Repaired With Bonded Composite Patch, Michael A. Hansen

Theses and Dissertations

This research focuses on investigating the mechanical behavior of cracked aluminum panels repaired with bonded boron/epoxy composite patches. The effects of crack initiation and growth on the residual strength of the repaired panels are characterized. This research establishes a correlation between damage modes, residual strength and evolution of strain within as well as outside the patch. Monotonic tensile tests on specimens with a perfectly bonded patch were used to determine the base line strength. Likewise, fatigue tests on specimens with a perfectly bonded patch served to establish baseline fatigue life. In addition, several specimens with a perfectly bonded patch were …

Internal Damage Detection And Assessment In Beams Using Experimental Natural Frequencies, Frances K. Durham

Theses and Dissertations

This study investigated the frequency response of a cantilever beam with the intent of establishing a reliable nondestructive method of damage detection. The test specimens were 12 aluminum 2024 T3 beams, each identical except for a unique, eccentrically located notch, and one reference notchless beam. The machined notches varied in length and location to simulate varying degrees of damage. Laser doppler vibrometry enabled the data acquisition. The changes in natural frequencies were correlated to notch length and notch location. A comparison of eccentric and centered notch influence on the natural frequencies also is discussed.

A Method To Calculate The Femoro-Polyethylene Contact Pressures In Total Knee Arthroplasty In-Vivo, Adrija Sharma

Masters Theses

This study deals with the development of a computational method that generates the in-vivo contact pressures on the superior side of the polyethylene in total knee arthroplasty (TKA) based on in-vivo kinematic data. Ten clinically successful subjects (five fixed and five mobile bearing TKA), having Hospital for Special Surgery (HSS) knee scores greater than 90, were analyzed under fluoroscopic surveillance while performing a weight-bearing deep knee bend. 3D in-vivo contact positions and kinematics, determined using a 2D to 3D registration technique, and soft tissue locations derived from literature were entered into a 3D inverse dynamics mathematical model to determine the …

Synthesis And Analysis Of Anionic Hydrogel Scaffolds For Endothelial Cell Tissue Engineering, Abitha Sundararajan

Masters Theses

Acidic hydrogels are cross-linked polymer networks that contain neutral and negatively charged monomers. The degree of negative charge on these soft materials plays a critical role in their biomedical applications. In particular, their use as a scaffold for cardiovascular applications depends on their charged and swollen states. The amount of negative charge, however, is a complicated function of the fabrication conditions, monomeric dissociation constants, ionic strengths and pH of the surround bath solution. This study, therefore, considered four representative acidic hydrogels and their physical properties and interactions with endothelial cells. The acidic monomers methacrylic acid (MAAc) and sulfoethylmethacrylate (SEMA) were …

A Validation Simulation Of A Large Pool Fire, W. Reid Williams

Masters Theses

The capabilities of the Fire Dynamics Simulator (Version 3) (FDS3) have been examined to determine whether a large pool fire test can be reasonably simulated. Activities undertaken include 2-D and 3-D pool fire modeling in the absence of wind and heat sinks within the fire principally to compare flame height predictions to established correlations, wind field modeling specifically targeted at developing initial velocity and boundary conditions to use in the simulation of an actual pool fire, and simulation of a specific pool fire test conducted by Sandia National Laboratories in 1983. Processes were developed for determining flame heights based on …

Assessments Of Vibratory Handheld Tools And Handle Interactions, Douglas Alan Logsdon

Masters Theses

There has been a broad history of injuries occurring as the result of vibratory hand-tool use. Following these findings, three human safety standards have been proposed. These standards declare that the dynamic properties with respect to acceleration frequency spectra must be determined for vibratory hand tools. These properties must meet specific tolerances in order to be considered acceptable for use.

The standards, however, do not recognize the significance of the coupling characteristics and the energy transfer between the user and vibrating handle. This interaction reveals the amount of vibratory energy that enters the user's hands. Epidemiological data for VWF shows …

Dynamic Response Analysis Of The Human Knee Joint, Brandi L. Bohleber

Masters Theses

Objective. To perform frequency response analysis of passive intact and rneniscectomized human knee joints under body mass. The knee dynamic system parameters and their alterations with different preloads and displacement amplitudes will be determined.

Design. Using an Instron Mechanical Testing System, specially designed fixtures, and the following softwares: WaveMaker, Excel, LabView, and Matlab, the knees were dynamically tested and analyzed.

Background. Studies have been performed to analyze the dynamic behavior of the human knee. However, no experimental study has investigated the dynamic response of the knee joint under an axial compressive dynamic loading condition considering the effect of the upper …

Polyampholyte Hydrogel Characteristics And Detecting The Bacterial Interactions With These Hydrogels Using Digital Image Processing Methods, Ram Pratap Gangadharan

Masters Theses

In recent years, the unique physical properties of synthetic hydrogels have been exploited in a number of interesting and novel applications. In particular polyampholytes have been the subject of many theoretical studies since they provide a model for studying the longrange interactions found in proteins and other forms of soft condensed matter. In balanced polyampholytes the net electrostatic forces are attractive so that in low ionic salt concentration, the chains have a tendency to collapse into compact globules. Addition of salt, which screens these interactions, induces a swelling of the chain. However the electrostatic interactions between polymeric and mobile charges …

Steady State Stress In A Coated Infinite Half-Space Subjected To A Moving Load, Jason M. Cruthirds

Theses and Dissertations

This research investigates the use of coatings to mitigate the stress distribution into an infinite half-space. High energy impact phenomenon at velocities exceeding the speed of sound is an important area of interest to the Air Force Research Laboratory. Holloman Air Force Base's High Speed Test Track sustains significant damage due to this phenomenon. In this thesis, the track system and coating are modeled analytically with equations of motion in terms of linear displacements. Coating thickness and material properties of epoxy or polymer laminates are investigated to understand their affect of stress distribution in the rail. An analytic solution is …

Fatigue Behavior Of A Functionally-Graded Titanium Matrix Composite, Scott R. Cunningham

Theses and Dissertations

Functionally-graded Titanium Matrix Composites are an attempt to utilize the high-strength properties of a titanium matrix composite with a monolithic alloy having the more practical machining qualities. This work studied the mechanical characteristics of the joint region as a first step toward future evaluation of this material. The scope of this effort involved testing under monotonic tension and fatigue loading conditions. Mechanical properties and cyclic behavior were evaluated for the joint area and then compared to those of the parent materials. The results of this study found that the strength of the transition region was slightly higher than the unreinforced …

Tensile Stress Rupture Behavior Of A Woven Ceramic Matrix Composite In Humid Environments At Intermediate Temperature, Kevin J. Larochelle

Theses and Dissertations

Stress rupture tests on the Sylramic^TM fiber with an in-situ layer of boron nitride, boron nitride interphase, and SiC matrix ceramic matrix composite were performed at 550°C and 750°C with 0.0, 0.2, or 0.6 atm partial pressure of water vapor, pH₂O. The 550°C, 100-hr strengths were 75%, 65% and 51% of the monotonic room temperature tensile strength, respectively. At 750°C, the strengths were 67%, 51%, and 49%, respectively. Field Emission Scanning Electron Microscopy analysis estimated the total embrittlement times for 550°C with 0.0, 0.2, and 0.6 atm pH₂O were >63 hrs, >38 hrs, and between …

Analysis Of Computational Methods For The Treatment Of Material Interfaces, Minh C. Nguyen

Theses and Dissertations

Rocket sled tests at the Air Force Research Laboratory's Holloman High Speed Test Track frequently approach velocities where gouging development becomes the limiting factor to achieving higher operating velocities. Direct observation of the gouging process is not possible so computational modeling is necessary to study the phenomenon. Since gouging development is dependent on the impact surface conditions, the method used to model material interfaces directly affects the accuracy of the solution. Three methods are available in the hydrocode CTH to handle material interfaces: 1) materials are joined at the interface, 2) a frictionless slide line is inserted, and 3) a …

An Investigation Of A Simplified Gouging Model, Gregory S. Rickerd

Theses and Dissertations

Gouging is a type of structural failure that becomes important when two metals slide against each other at velocities in the range of 1.5 kilometers per second. A computer model has previously been used to model the development of gouging at the Holloman High Speed Test Track. This model has not been experimentally verified to be correct, due to the complexity of the model. This research develops a simplified model that can be experimentally verified. The computer program utilized in this research was studied to determine the most appropriate options to use in simulations. This was accomplished by modeling a …

Creep-Rupture Behavior Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperatures In Air And Steam Environments, Lee B. Harlen

Theses and Dissertations

Oxide/oxide ceramic matrix composites (CMCs) are being considered for applications such as jet engine combustion chambers and afterburner flaps. Nextel™ 720/A (N720/A), an oxide/oxide CMC with an alumina matrix and no interphase at the fiber-matrix interface, was developed specifically to provide improved long-term properties and performance at 1200°C. This study focused on experimental investigation of creep behavior of N720/A [0/90] at elevated temperatures in laboratory air and in 100% steam environment. Monotonic tensile tests to failure were performed at 23, 1200, and 1330°C. Ultimate tensile strength (UTS) values were established and monotonic stress-strain curves were produced. Creep-rupture tests at 1200°C …

Using Neural Networks To Identify The Effect Of Construction Factors On The Cost Of Reinforced Concrete Elements, Ahmed Aly El-Sotouhy

Archived Theses and Dissertations

No abstract provided.

Engineering Tools For Variable Stiffness Vibration Suppression And Isolation, Michael F. Winthrop

Theses and Dissertations

With the advent of smart materials, the concept of semi-active control or dynamic control of stiffness and/or damping for vibration control of structures has become practical and has seen limited use. Semi-active control has advantages over active and passive control methods, since it provides almost as much capability as active control while requiring much less power. Its main disadvantage is its inherent nonlinearity, greatly complicating engineering design. The purpose of this research is to extend semi-active control vibration isolation tools and methods considering space launch and on-orbit systems.

Effect Of Microstructure And Alloying Elements On The Resistance Of Fastener Grade Steels To Hydrogen Assisted Cracking , Nicholas E. Nanninga

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

Fastener grade steels with varying alloy contents and heat treatments were employed to measure changes in resistance to hydrogen assisted cracking. The testing procedure compared notched tension specimens fractured in air to threshold stress values obtained during hydrogen charging, utilizing a rising step load procedure. Bainitic structures improved resistance by 10-20% compared to tempered martensite structures. Dual phase steels with a tempered martensite matrix and 20% ferrite were more susceptible and notch sensitive. High strength, fully pearlitic structures showed an improvement in resistance. Carbon content, per se, had no effect on the resistance of steel to hydrogen assisted cracking. Chromium …

Rf-Sputter Fabrication Of Magnetic Garnet Thin Films And Simulation Modeling For 1-D Magnetic Photonic Crystal Waveguide Devices, Haichun Yang

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

One dimensional magnetic photonic crystals (1D-MPC) are promising structures for integrated optical isolator applications. Rare earth substituted garnet thin films with proper Faraday rotation are required to fabricate planar 1D-MPCs. In this thesis, flat-top response 1D-MPC was proposed and spectral responses and Faraday rotation were modeled. Bismuth substituted iron garnet films were fabricated by RF magnetron sputtering and structures, compositions, birefringence and magnetooptical properties were studied. Double layer structures for single mode propagation were also fabricated by sputtering for the first time.

Multilayer stacks with multiple defects (phase shift) composed of Ce-YIG and GGG quarter-wave plates were simulated by the …

Supercritical Fluid Extraction Of Rice Bran With Adsorption On Rice Hull Ash, Paresh Manilal Patel

LSU Doctoral Dissertations

Rice bran oil was extracted using environmentally-friendly supercritical carbon dioxide at varying conditions. Experimental treatments included pressure (27.6, 41.4 and 55.2 MPa), temperature (40 and 60 oC) and flow rates (25, 45 and 65 g/min) of supercritical carbon dioxide. Extracts collected at different time intervals during 4-hour extraction runs in a 3-L extractor were analyzed for oil yield and antioxidants. Normal-phase HPLC was used for analyzing the extract for important antioxidant compounds of oryzanol, tocopherols, tocotrienols. Silica rich rice hull ash adsorbent was also incorporated in combined extraction-adsorption experiments under similar supercritical fluid conditions. Supercritical extraction yields of rice bran …

A Tablet Pc Application For Construction Site Safety Inspection And Fatality Prevention, Prabhu Sunkara

LSU Master's Theses

Construction industry accounts for the largest number of occupational injuries and fatalities every year. Occupational Safety and Health Administration (OSHA) is an organization responsible for regulating and enforcing standards for various occupations to ensure safe working conditions including construction industry. As an OSHA requirement, every construction employer should employ a safety program that involves both training of the employees and frequent site inspections. OSHA has provided an online ‘construction eTool’ as a training tool which also aids in the development of safety inspection procedures. Traditionally, safety inspections are paper based and usually designed to address a specific work area or …

Development Of High Performance Hybrid Syntactic Foams: Structure And Material Property Characterization, Rahul R. Maharsia

LSU Doctoral Dissertations

Syntactic foams are light weight particulate composites that use hollow particles (microballoons) as reinforcement in a polymer resin matrix. High strength microballoons provide closed cell porosity which helps in reducing weight of the material. Due to their wide range of possible applications such as in aerospace and marine structures, it is desirable to modify the physical and mechanical properties of syntactic foams as per the requirements of an application. Various filler materials can be used to modify the foam microstructure to attain these desired properties. Compression tests have revealed that high density syntactic foams demonstrate poor damage tolerance and low …

Purification And Structural Characterization Of Caged Dna Oligonucleotides, Brendan Michael Mcadams

LSU Master's Theses

“Cage” molecules reversibly block the bioactivity of a target substrate molecule by a photolyzable covalent bond formed at a functional site of the target molecule. The attachment of cage molecules to DNA oligodeoxynucleotides (ODNs) to transiently block bioactivity, and site-specific restoration of bioactivity using targeted light exposure, would enable a new method of control for use in gene therapy, molecular/DNA computing, molecular biology, and drug delivery. The reaction of the cage molecule 1-(4,5-dimethoxy-2-nitrophenyl)diazoethane (DMNPE) with DNA ODNs in an batch reaction yields a mixture of products with varying degrees of caging. Purification and verification of the hypothesized site of DMNPE …

Evidence Of Neotectonic Activity In Southwest Louisiana, Jordan Oliver Heltz

LSU Master's Theses

A methodology that combines high-resolution topographic mapping, field observations, subsurface evaluation, and geodetic data analysis has successfully located several fault-related geomorphic steps in an area of southwestern Louisiana once thought to be relatively devoid of such features. Comparison of height differences of benchmarks straddling these suspected fault-related steps shows that vertical displacement rates on faults in the study area ranged from about 2 mm/yr to as much as 6 mm/yr during the 1960’s and 1970’s. However, leveling data obtained as recently as January 2005 reveals that the majority of these faults are currently moving at rates of less than 1 …