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2009

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Articles 571 - 596 of 596

Full-Text Articles in Mechanical Engineering

On-Line Depth Measurement Of Micro-Scale Laser Drilled Holes, Rock Allen Powell Jan 2009

On-Line Depth Measurement Of Micro-Scale Laser Drilled Holes, Rock Allen Powell

Masters Theses

"A micron-precision micro-hole depth detection scheme has been developed which utilizes a confocal structure and a photomultiplier tube as a photodetector. This scheme is experimentally confirmed to posses an accuracy of greater than 95% for micro-holes on the order of one-hundred microns in diameter and tens of microns in depth and could be easily be integrated for the control of industrial and research oriented laser micro-machining process"--Abstract, page iii.

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Selection Of Pressure Equation For Preliminary Planing Hull Design Using Modified Analytical Hierarchy Process, Pamela Sue Fergen Jan 2009

Selection Of Pressure Equation For Preliminary Planing Hull Design Using Modified Analytical Hierarchy Process, Pamela Sue Fergen

Mechanical & Aerospace Engineering Theses & Dissertations

In the early stages of design when data availability is limited, engineers often times rely upon experience and regression analysis to select the most suitable design equation among many competitive ones. This study presents an alternative that applies a modified Analytical Hierarchy Process (AHP) to select the most suitable design equation. The Analytical Hierarchy Process, a multi-criteria decision making method, has been utilized in the business and management world to collect and evaluate experts' opinions in order to arrive at a final decision. The Analytical Hierarchy Process employed here will treat each of the design equations as an expert and …

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Singular Superposition/Boundary Element Method For Reconstruction Of Multi-Dimensional Heat Flux Distributions With Application To Film Cooling Holes, Mahmood Silieti, Eduardo Divo, Alain J. Kassab Jan 2009

Singular Superposition/Boundary Element Method For Reconstruction Of Multi-Dimensional Heat Flux Distributions With Application To Film Cooling Holes, Mahmood Silieti, Eduardo Divo, Alain J. Kassab

Publications

A hybrid singularity superposition/boundary element-based inverse problem method for the reconstruction of multi-dimensional heat flux distributions is developed. Cauchy conditions are imposed at exposed surfaces that are readily reached for measurements while convective boundary conditions are unknown at surfaces that are not amenable to measurements such as the walls of the cooling holes. The purpose of the inverse analysis is to determine the heat flux distribution along cooling hole surfaces. This is accomplished in an iterative process by distributing a set of singularities (sinks) inside the physical boundaries of the cooling hole (usually along cooling hole centerline) with a given …

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Experimental Investigation Of A Meso-Scale Axial Flow Pump, Jonathon Ray Bice Jan 2009

Experimental Investigation Of A Meso-Scale Axial Flow Pump, Jonathon Ray Bice

Open Access Theses & Dissertations

The scope of this work involves the testing of an experimental meso-scale axial flow pump intended for use in micro-spacecraft and micro-satellites. A setup was implemented to test pressure and flow characteristics at different velocities for three configurations of the pump. In addition, an alternate setup was used to test torque and efficiency. Computational fluid dynamics simulations were also conducted. The results are presented and analyzed to determine whether the pump is a viable alternative for the space industry.

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Insight Into The Physics Of Rupture: Dynamic Triggering Seismicity, Hector Gonzalez-Huizar Jan 2009

Insight Into The Physics Of Rupture: Dynamic Triggering Seismicity, Hector Gonzalez-Huizar

Open Access Theses & Dissertations

Seismic waves can trigger earthquakes and tremor at large distances from the causable event. Dynamic triggering occurs when the surface waves from large earthquakes change the stresses conditions on previously overstressed faults, promoting failure. To understand the causative stresses and environments behind dynamic triggering, we model the change in the stress field that the passing of Rayleigh and Love waves cause on a fault plane of arbitrary orientation relative to the direction of propagation of the waves, and apply a Coulomb failure criterion to calculate the potential of these stress changes to trigger seismicity. We apply our model to three …

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Effect Of Air Addition On Plasma-Based Reforming Of Methane And Propane, Atul Vitthalrao Ambhore Jan 2009

Effect Of Air Addition On Plasma-Based Reforming Of Methane And Propane, Atul Vitthalrao Ambhore

Open Access Theses & Dissertations

No abstract provided.

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Laminar Burning Velocities Of Gas Mixtures, Vishwanath Reddy Ardha Jan 2009

Laminar Burning Velocities Of Gas Mixtures, Vishwanath Reddy Ardha

Open Access Theses & Dissertations

In this study, burning velocities of hydrogen-carbon monoxide (H2-CO) mixtures, which are primary constituents of syngas fuels, are measured. The effect of different burner systems, H2 concentration, and different measurement techniques on the burning velocities of H2-CO mixtures is also discussed. The burning velocities of H2-CO mixtures increase with the increase in H2 content in the mixture. When compared with different burner systems using different methods, the burning velocity data almost coincide in the lean condition, but at rich condition the data stray away from each other. The burning velocities of actual syngas compositions (based on different sources of coal) …

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A Multi-Function, Disposable, Microfluidic Module For Mutation Detection, Tae Yoon Lee Jan 2009

A Multi-Function, Disposable, Microfluidic Module For Mutation Detection, Tae Yoon Lee

LSU Doctoral Dissertations

Recognition of point mutations in a codon 12 of the K-ras gene, most frequently observed, is considered to be useful in the early diagnosis of several types of the human cancers. We have developed a multifunction, disposable, microfluidic module which detects low-abundant point mutations in human genomic DNA in modular architecture. Each functional component including a microfluidic PCR reactor, a passive diffusional micromixer reactor, and a microfluidic LDR reactor was separately designed and fabricated. Fluidic interconnects were also developed to make a fluidic passage between the functional components. Polycarbonate substrates were micro-molded, using hot embossing with micro-milled brass mold inserts …

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Multiphase Flows In Polymer Microfluidic Systems, Namwon Kim Jan 2009

Multiphase Flows In Polymer Microfluidic Systems, Namwon Kim

LSU Doctoral Dissertations

Continuous delivery of segmented reagents using pressure-driven multiphase flow in microchannels is a promising technology for high throughput microfluidic bioassays. Separation and encapsulation of the target reagents with another inert fluid provide many advantages over single phase flow in microfluidic applications of biotechnology. In order to achieve these advantages and control these multiphase flows, it is necessary to understand their generation and transport characteristics as influenced by geometrical miniaturization, channel wall properties, the effects of surfactants and operating conditions. For gas-liquid two-phase flow, dry air and deionized water were driven into hot embossed PMMA microchannels with 200 μm square test …

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A Modular Approach To High Throughput Microsystems, Pin-Chuan Chen Jan 2009

A Modular Approach To High Throughput Microsystems, Pin-Chuan Chen

LSU Doctoral Dissertations

A modular high throughput microsystem was developed using microfabrication technology and nucleic acid analysis. The purpose of developing this microsystem is to identify acute infectious disease and prevent contagious outbreak in a matter of time. This microsystem included three major components, a reagent distribution device, a 96 CFPCR array, and a multi-zone thermal system, to efficiently amplify specific DNA fragments to determine the disease status or precisely pinpoint a disease from multiple patients. Polymerase chain reaction (PCR) is the key component in the nucleic acid analysis for disease because it can be used to amplify interested DNA fragments by repeatedly …

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A Self Healing Smart Syntactic Foam Based Grid Stiffened Sandwich Structure, Manu Kuruvila John Jan 2009

A Self Healing Smart Syntactic Foam Based Grid Stiffened Sandwich Structure, Manu Kuruvila John

LSU Doctoral Dissertations

Syntactic foams are composite materials synthesized by dispersing microballoons in a polymeric, ceramic or metallic matrix. In the past three decades, syntactic foams have gained immense importance as a lightweight and damage-tolerant material when used in foam-cored sandwich structures. Because of the structural-length scale damages by low velocity impact such as tool drops, runway debris etc., sandwich structures usually have a very low residual structural capacity. Unfortunately, macro-length scale damage, in particular internal damage such as impact damage, is very difficult to repair. Therefore, there is a genuine need to develop impact-tolerant and self-healing syntactic foams which can be used …

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State Feedback Control With Time Delay, Akshay Nareshraj Singh Jan 2009

State Feedback Control With Time Delay, Akshay Nareshraj Singh

LSU Doctoral Dissertations

In this thesis we start with an introduction to the theory of vibration control. We broadly classify the control methods into passive and active schemes. We introduce the problem of state feedback control and provide the classical solution in the form of Ackermann formula. We then identify the limitations of the classical approach and present the more elegant solution of partial pole assignment without spillover. We highlight the problem with model uncertainties and describe the method of pole assignment using data from measured receptances. This approach is extended for pole assignment for a linear vibrating system by using state feedback …

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Meso-Scale Heating Predictions For Weak Impact Of Granular Energetic Solids, Rohan Panchadhara Jan 2009

Meso-Scale Heating Predictions For Weak Impact Of Granular Energetic Solids, Rohan Panchadhara

LSU Doctoral Dissertations

An explicit, two-dimensional, Lagrangian finite and discrete element technique is formulated and used to computationally characterize meso-scale fluctuations in thermomechanical fields induced by low pressure deformation waves propagating through particulate energetic solids. Emphasis is placed on characterizing the relative importance of plastic and friction work as meso-scale heating mechanisms which may cause bulk ignition of these materials and their dependence on piston speed (vp ~ 50-500 m/s). The numerical technique combines conservation principles with a plane strain, thermoelastic-viscoplastic constitutive theory to describe deformation within the material meso-structure. An energy consistent, penalty based, distributed potential force method, coupled to a penalty …

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Experimental And Numerical Modeling Of Stresses In Non-Conventional Cross-Sectioned Composite Pipes, Prashanth Ramachandran Jan 2009

Experimental And Numerical Modeling Of Stresses In Non-Conventional Cross-Sectioned Composite Pipes, Prashanth Ramachandran

LSU Master's Theses

Composite materials have been widely used in the ship-building, aerospace and construction industries because of their distinct advantages of low weight, high stiffness, and high strength to weight ratios. These properties are due to the low weight of the epoxy core matrix and high strengths of the glass/carbon fibers. Composite pipes used in various applications are traditionally spherical in cross-section. In this study, non-conventional cross-sectioned composite pipes [i.e. rectangular and triangular cross-sections] have been proposed, fabricated, tested and analyzed because of their ability to be bundled without loss of space. The behaviors of these pipes under an internal pressure test …

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Large Eddy Simulation Of Turbulent Premixed Combustion In Gas Turbines, Ashoke De Jan 2009

Large Eddy Simulation Of Turbulent Premixed Combustion In Gas Turbines, Ashoke De

LSU Doctoral Dissertations

An artificially Thickened Flame (TF) approach based on LES framework is used to model the turbulent premixed combustion in gas turbine combustors. A number of variants of the Thickened Flame approach including a modified version of TF model have been studied in details. In the TF model, the flame front is artificially thickened to resolve on LES computational grid. With this approach, reaction rate modeling does not require any ad-hoc closure assumptions. However, suitable modifications have to be made to compensate for flame thickening. To verify the predictive capability of the models, a stoichiometric methane-air flame on Bunsen burner type …

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Effects Of Processing Parameters On The Embrittlement Of Self Reacting Friction Stir Welds, David Eric Taylor Jan 2009

Effects Of Processing Parameters On The Embrittlement Of Self Reacting Friction Stir Welds, David Eric Taylor

LSU Master's Theses

Friction Stir Welding (FSW) has been adopted as one of the major welding processes for joining Aluminum. Many aerospace and marine structures are welded through this novel FSW processes currently. The Lockheed Martin Space Systems (LMSS), Michoud Operations, in New Orleans is continuously pursuing Friction Stir Welding technologies in its efforts to advance fabrication of the external tanks of the space shuttle. Recently, a reduction in mechanical strength (embrittlement) has been observed especially in self-reacting (SR) friction stir welds. This strength reduction was attributed to Residual Oxide Defects (ROD) but the exact reasons for this type of behavior needed to …

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Dynamical Investigation Of A Manned Capsule/Tether Re-Entry System, Jeffrey Alan Kornuta Jan 2009

Dynamical Investigation Of A Manned Capsule/Tether Re-Entry System, Jeffrey Alan Kornuta

LSU Master's Theses

The use of tethers in space has an exciting promise in future astronautical applications, with the possibility of providing more sophisticated functionality to satellites and spacecraft. Some of these applications include adjoining satellites, creating microgravity environments, generating power, and transferring momentum between spacecraft. The focus of this project is to investigate the possible reduction in convective heat flux and temperatures on a manned capsule as a result of re-entry with an attached momentum exchange tether, including how various tether parameters affect these results. Using a “bottom-up” approach by modeling the system as a series of lumped masses and rigid rods …

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Intracellular Ice Formation In Adult Stem Cells In The Presence Of Polyvinyl Pyrrolidone, Avishek Guha Jan 2009

Intracellular Ice Formation In Adult Stem Cells In The Presence Of Polyvinyl Pyrrolidone, Avishek Guha

LSU Master's Theses

The main objective of this work was to assess the effect of 10% (w/v) polyvinylpyrrolidone (PVP) on the pattern of intracellular ice formation (IIF) in human adipose tissue derived adult stem cells (ASCs) in the absence of serum and other cryoprotective agents (CPAs). Passage 1 (P1) ASCs were cultured, washed and suspended in either 1x PBS (Phosphate Buffered Saline) or 10% w/v solution of PVP in 1x PBS. The freezing experiments were carried out using a fluorescence microscope equipped with a Linkam™ cooling stage using two different temperature/time cooling protocols. Both the cooling protocols had a common cooling ramp: cells …

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Dynamics Of Vortical Structures In A Low-Blowing-Ratio Pulsed Transverse Jet, Clementine Vezier Jan 2009

Dynamics Of Vortical Structures In A Low-Blowing-Ratio Pulsed Transverse Jet, Clementine Vezier

LSU Master's Theses

Large Eddy Simulation is used to study the interaction of a 35° inclined jet into a crossflow. Steady state cases, with a BR ranging from 0.150 to 1.2, are firstly examined to understand the dynamics of the flow field. Iso-surface of Laplacian of the pressure, vorticity contour and velocity fields highlight the presence of four main vortical structures: shear layer vortices, horse-shoes vortices, wake vortices and CRVP. Qualitative comparisons are performed between simulations and experiments. The dynamics of the flow field is next characterized by pulsing the jet. The studied pulsed cases have same low BR and duty cycle respectively …

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Fatigue Fracture And Microstructural Analysis Of Friction Stir Welded Butt Joints Of Aerospace Aluminum Alloys, Vinay Raghuram Jan 2009

Fatigue Fracture And Microstructural Analysis Of Friction Stir Welded Butt Joints Of Aerospace Aluminum Alloys, Vinay Raghuram

LSU Master's Theses

Friction-Stir-Welding (FSW) has been adopted as a major process for welding Aluminum aerospace structures. Al-2195, which is one of the new-generation Aluminum alloys that has been used on the external tank of the new super lightweight external tank of the space shuttle. The Lockheed Martin Space Systems (LMSS), Michoud Operations in New Orleans is continuously pursuing Friction-Stir-Welding technologies in its efforts to advance fabrication of the external tanks of the space shuttle. The future launch vehicles which will have to be reusable, m, an dates the structure to have good fatigue properties, which prompts an investigation into the fatigue behavior …

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On The Effects Of Peripheral Sliding Velocity And Operating Differential Pressure In Rotary O-Ring Seals, Karan Lingerkar Jan 2009

On The Effects Of Peripheral Sliding Velocity And Operating Differential Pressure In Rotary O-Ring Seals, Karan Lingerkar

LSU Master's Theses

An O-ring seal is of paramount importance in hydraulic and pneumatic machinery used in oil and gas drilling processes. O-ring seals are generally employed to contain the environments of working fluids existing on either side of the seal from interacting with each other, to maintain a uniform pressure chamber and to eliminate the environmental contaminants that interact at the rubbing interface. Failure of dynamic O-rings in hydraulic and pneumatic machinery often results in considerable productivity loss to the chemical and petrochemical industries. Therefore, it is highly important to determine the life of an O-ring for these applications under various operating …

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Thermomechanical Characterization Of A Shape Memory Polymer Based Syntactic Foam, Damon Nettles Jan 2009

Thermomechanical Characterization Of A Shape Memory Polymer Based Syntactic Foam, Damon Nettles

LSU Master's Theses

Shape memory polymers (SMPs) are a type of smart material capable of “remembering” multiple shapes and transitioning between them in response to an external stimulus. They offer the potential to self-seal macro-length scale damage in a nearly autonomous fashion. Syntactic foams are lightweight structural materials currently used in the marine and aerospace industries. This study seeks to bring syntactic foams and SMPs together, retaining characteristics of both components, to create a low-density smart composite. The SMP based syntactic foam is used as the core of a grid stiffened sandwich structure capable of healing impact damage multiple times. In order to …

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Manufacture, Characterization, And Application Of Multiwall Carbon Nanotube Composite Crylonitrile-Butadiene-Styrene, Daniel Ray Bortz Jan 2009

Manufacture, Characterization, And Application Of Multiwall Carbon Nanotube Composite Crylonitrile-Butadiene-Styrene, Daniel Ray Bortz

University of Kentucky Master's Theses

Carbon nanotubes have been studied for nearly two decades and their amazing properties continue to spur intense investigation in the area of polymer composites. In terms of potential commercialization, mutiwall carbon nanotubes (MWCNTs) are currently the most prevalent and economically viable form of nanotubes. Uncovering innovative means to take full advantage of their properties remains a fundamental issue. In this thesis, viability of their use to reinforce polymeric systems is reported. Acrylonitrilebutadiene- styrene (ABS) was used as the host matrix. MWCNTs were introduced to the ABS matrix via melt compounding. The resulting composite was thoroughly rheologically, thermally, and mechanically characterized. …

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Detailed Surface Analysis Of Lip Seal Elastomers Ran Against Shafts Manufactured With Triangular Cavities, Vetrivel Kanakasabai Jan 2009

Detailed Surface Analysis Of Lip Seal Elastomers Ran Against Shafts Manufactured With Triangular Cavities, Vetrivel Kanakasabai

University of Kentucky Master's Theses

Previous experimental and theoretical results indicate that the keys to successful radial lip seals are the surface characteristics of the shaft and the microasperity pattern that develops due to wear on the elastomer. In this study, the lip seal was tested against five different patterns of shaft surface: plain stainless steel, triangular cavities oriented towards air, triangular cavities oriented towards oil, triangular cavities leading and triangular cavities lagging. Using Zygo optical profilometer and scanning electron microscope, a thorough surface characterization of the micro-asperities and microcavities is done on the lip seal elastomer. Correlation coefficients were calculated between the surface parameters …

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Self-Healing Of Fiber Reinforced Polymer Compoistes [Sic], Nebiyu Fikru Jan 2009

Self-Healing Of Fiber Reinforced Polymer Compoistes [Sic], Nebiyu Fikru

LSU Master's Theses

The study of self-healing materials is inspired by biological systems in which damage triggers an autonomous healing response. In recent years, this concept of autonomic healing material, where initiation of repair is integral to the material, is being considered for engineering applications. The concept offers the designer an ability to incorporate secondary functional ability of counteracting service degradation in addition to achieving the primary, usually structural integrity, requirement. Self-healing materials also have the benefit of offering lighter and optimized structures as well as reduced maintenance cost. Previous works on polymer matrix composites have shown that significant fractions of mechanical properties …

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Aerodynamic And Heat Transfer Studies In A Combustor-Fired, Fixed-Vane Cascade With Film Cooling, James William Post Jan 2009

Aerodynamic And Heat Transfer Studies In A Combustor-Fired, Fixed-Vane Cascade With Film Cooling, James William Post

LSU Master's Theses

Pressure and heat transfer data has been generated in a high-pressure, high-temperature vane cascade. This cascade differs from many others seen in typical low-pressure facilities using room temperature air. Primarily, a natural gas-fired combustor generates realistic turbulence profiles in the high-temperature exhaust gases that pass through the vane cascade. The fixed-vane cascade test sections have film cooling holes machined into the surfaces in arrangements that closely model configurations seen in real-life first-row nozzle guide vanes (NGV). Theoretical coolant jet-to-crossflow blowing ratios (M) range from 0.5 to 3.0. Coolant jet-to-crossflow theoretical density ratios (DR) used for typical tests vary between 1.0 …

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