Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Hot wire anemometry (2)
- Magnetic field (2)
- 3D measurements with x-probe (1)
- ANSYS (1)
- Active tilting-pad bearing (1)
-
- Adaptive control (1)
- Adult stem cells (1)
- Advanced grid stiffened (1)
- Amorphous carbon (1)
- Anisotropy (1)
- Annealing (1)
- Asymptotic method (1)
- Atmospheric boundary layer modeling (1)
- Axis switching (1)
- Axis-switching (1)
- Brain boundary diffusion (1)
- Chemical vapor deposition (1)
- Coaxial jets (1)
- Coercivity (1)
- Combustion (1)
- Compliant journal bearings (1)
- Compressible Reynolds equation (1)
- Contact problems (1)
- Copper (1)
- Cosmos/m (1)
- Creep (1)
- Creep rate (1)
- Cryopreservation (1)
- Cryoprotectants (1)
- Cte (1)
Articles 1 - 28 of 28
Full-Text Articles in Mechanical Engineering
Experimental And Numerical Study Of Feeding Channel In Proton Exchange Membrane Fuel Cell, Abul Bashar Mahmud Hasan
Experimental And Numerical Study Of Feeding Channel In Proton Exchange Membrane Fuel Cell, Abul Bashar Mahmud Hasan
LSU Master's Theses
The performance of a Proton Exchange Membrane Fuel Cell (PEMFC) using different feeding configurations has been studied, with a focus on the water flooding due to electrochemical reaction. Feeding channel or Bipolar plate in Proton Exchange Fuel Cell is a dominating part. As feeding channel keeps direct contact with the gas diffusion layer, it helps efficiently supplying fuel and air into the gas diffusion layer for efficient production of electricity. Experimental data have been taken at hydrogen flow rates of 20,40,60,80,100 sccm for various bipolar plate arrangements. Three bipolar plates, namely serpentine, straight channel and interdigitated designs, were arranged in …
Thermal Management Of The Lsu Micro Gas Chromatograph, Praveen K. Pasupuleti
Thermal Management Of The Lsu Micro Gas Chromatograph, Praveen K. Pasupuleti
LSU Master's Theses
Gas chromatography is a technique widely used for the separation and analysis of gas samples. Gas chromatographs are used for environmental maintenance, monitoring sophisticated biological analyses, and to separate components from a mixture of gases for mass spectrometer analysis. There has been a tremendous interest in miniaturization of gas chromatograph systems because of the potential for portability, faster response time, lower dead volume, lower power consumption, and lower cost of operation. Conventional gas chromatography keeps the column at a constant temperature during separation, which is called isothermal analysis. Temperature programming is a mode of gas chromatography in which the column …
Pressure-Velocity Correlation Study On 1:50 Scale Model Of The Ttu Wind Engineering Research Field Lab Building, Praveen Kumar
Pressure-Velocity Correlation Study On 1:50 Scale Model Of The Ttu Wind Engineering Research Field Lab Building, Praveen Kumar
LSU Master's Theses
The goal of the present study is to investigate the relationship between incident wind velocity fluctuations and the surface pressure fluctuations on the roof of a low rise building. The goal was fulfilled by studying the pressure velocity correlation on 1:50 scale model of a typical low rise building, the Wind Engineering Research Field Laboratory (WERFL) building located at Texas Tech University, Lubbock. The experimental study was carried out in the LSU Wind Tunnel Laboratory by simulating the boundary layer prevalent at the full-scale site. The velocity profile in the boundary layer was measured using the TSI Hot-Wire system with …
Structural Integrity And Fatigue Crack Propagation Life Assessment Of Welded And Weld-Repaired Structures, Mohammad Shah Alam
Structural Integrity And Fatigue Crack Propagation Life Assessment Of Welded And Weld-Repaired Structures, Mohammad Shah Alam
LSU Doctoral Dissertations
Structural integrity is the science and technology of the margin between safety and disaster. Proper evaluation of the structural integrity and fatigue life of any structure (aircraft, ship, railways, bridges, gas and oil transmission pipelines, etc.) is important to ensure the public safety, environmental protection, and economical consideration. Catastrophic failure of any structure can be avoided if structural integrity is assessed and necessary precaution is taken appropriately. Structural integrity includes tasks in many areas, such as structural analysis, failure analysis, nondestructive testing, corrosion, fatigue and creep analysis, metallurgy and materials, fracture mechanics, fatigue life assessment, welding metallurgy, development of repairing …
Modeling And Experimentation Of Drying Of Adipose Derived Adult Stem Cells, Surbhi Mittal
Modeling And Experimentation Of Drying Of Adipose Derived Adult Stem Cells, Surbhi Mittal
LSU Master's Theses
Development of protocols for storing desiccated cells at ambient temperatures offers tremendous economic and practical advantages over traditional storage procedures such as cryopreservation and freeze-drying. An integrated frame work of experimentation and modeling is adopted in the present work to develop procedures for storage of adult stem cells at ambient temperature. As a first step, we have measured the post-rehydration membrane integrity of two passages, Passage-0 (P0) and Passage-1 (P1), of human adipose-derived stem cells (hASCs). hASCs were dried using a convective stage at three different drying rates (slow, moderate and rapid) in D-PBS with trehalose (50 mM) and glycerol …
An Evaluation Of Ansys Contact Elements, Serhan Sezer
An Evaluation Of Ansys Contact Elements, Serhan Sezer
LSU Master's Theses
The ANSYS code offers stress analysts a variety of contact element options: point-to-surface or surface-to-surface and low-order or high-order elements, in concert with any one of five contact algorithms (augmented Lagrangian, penalty method, etc.). This raises questions as to what option performs best under what circumstances. Here we offer some answers to these questions by examining performance in some numerical experiments. The numerical experiments focus on frictionless contact with a rigid indenter; even so, the number of experiments involved is quite large. The experiments use a battery of test problems with known analytical solutions: contact patch tests with nodes matching …
Simulations And Experimental Analysis Of High-Aspect-Ratio Diffusive Micro-Mixers, Amit Maha
Simulations And Experimental Analysis Of High-Aspect-Ratio Diffusive Micro-Mixers, Amit Maha
LSU Master's Theses
Passive (diffusional) mixing has been used in designing high-aspect-ratio micro-mixers for the purpose of performing the Liagase Detection Reaction (LDR). A simple model was used to design such mixers optimized for pressure drop or time required to deliver a prescribed volume of mixture. The types of mixers considered are simple, cheap, and durable and can perform over a broad range of volumetric flow rates at reasonably modest pressure drops. The fluids typically have a very low diffusion coefficient of=1.2x10^10m^2/s, and thus diffusional mixing can only be effective in high-aspect-ratio micro-channels. A realizable aspect ratio of 6 has been considered initially …
Fabrication Of High Aspect Ratio Vibrating Cylinder Microgyroscope Structures By Use Of The Liga Process, Yohannes Mamo Desta
Fabrication Of High Aspect Ratio Vibrating Cylinder Microgyroscope Structures By Use Of The Liga Process, Yohannes Mamo Desta
LSU Doctoral Dissertations
Inertial grade microgyroscopes are of great importance to improve and augment inertial navigation systems based on GPS for industrial, automotive, and military applications. The efforts by various research groups worldwide to develop inertial grade microgyroscopes have not been successful to date. In 1994, the Department of Mechanical Engineering at Louisiana State University and SatCon Technology Corporation (Boston, Massachusetts) proposed a series of shock tolerant micromachined vibrating cylinder rate gyroscopes with aspect ratios of up to 250:1 to meet the needs of inertial navigation systems based on existing conventional vibrating cylinder gyroscopes. Each microgyroscope consisted of a tall thin shell metallic …
Simulation Of A Micro Jet Cooling Array, Pierre Montanier
Simulation Of A Micro Jet Cooling Array, Pierre Montanier
LSU Master's Theses
The new generation of electronic devices are more powerful, and they produce more heat. Hence, there is a need for micro cooling systems for removing the heat from these micro chips. This research focused on one micro cooling system-the micro jet cooling array. Some test simulations were made on a single jet cooling system. In addition, the inlet Reynolds number was varied in order to obtain the variation of the heat transfer coefficient. These simulations gave a basic idea of how the impingement cooling method works on the micro jet cooling array. Numerical simulations were made on the actual micro …
Flame Synthesis Of Carbon-Nanostructures, Saritha Perla
Flame Synthesis Of Carbon-Nanostructures, Saritha Perla
LSU Master's Theses
Ever since their discovery carbon nanostructures (nanotubes and nanofibers) have attracted a lot of interest, due to their striking physical, chemical, mechanical and electrical properties, and paves the path to a wide range of applications. Large quantities of these structures are necessary to make their applications viable. The challenge is to produce them in bulk and in an economical way. Current methods like Arc discharge have the disadvantages of short tube lengths, CVD generated nanomaterials are often riddled with defects and although laser ablation method produces pure and high yield of nanotubes, is a costly technique with expensive lasers and …
Molecular Dynamics Simulations Of Biological Membranes In The Presence Of Cryoprotectants, Dinesh Pinisetty
Molecular Dynamics Simulations Of Biological Membranes In The Presence Of Cryoprotectants, Dinesh Pinisetty
LSU Master's Theses
Cryopreservation is a process that is characterized by the transport of water and cryoprotectants through the cell membrane. This phenomenon has been studied in extensive detail at the macroscopic (µm) scale but in a somewhat more limited fashion at the microscopic (nm) scale. In this study we develop several lipid bilayer models to approximate a cell membrane (nm) and present the effect of several different cryoprotectants on the structural characteristics of these lipid bilayers using molecular dynamic simulations. The lipid bilayer models included dipalmitoylphosphatidylcholine (DPPC), dimyristoylphosphatidylcholine (DMPC) and palmitoyleylphosphatidylcholine (POPC) while the cryoprotectants included methanol and dimethylsulfoxide (DMSO). The molecular …
Intrinsic Stress And High Temperature Properties Of Metal-Contanining Hydrogenated Amorphous Carbon Coatings, Bo Shi
LSU Doctoral Dissertations
A detailed examination of the intrinsic stress development and mechanical properties of titanium-containing hydrogenated amorphous carbon (Ti-C:H) and W-C:H coatings, deposited in an inductively coupled plasma (ICP) assisted hybrid chemical/physical vapor deposition (CVD/PVD) environment was carried out. Intrinsic stresses within those coatings were found to be compressive and dependent on compositions. The intrinsic compression within Ti-C:H was further shown to be significantly influenced by the energy of ionic species bombarding the substrate during growth. The results suggested that ion bombardment played a significant role in intrinsic stress generation within Ti-C:H, and was likely to influence stress development in other low …
Nonlinear Control And Its Application To Active Tilting-Pad Bearings, Zhijun Cai
Nonlinear Control And Its Application To Active Tilting-Pad Bearings, Zhijun Cai
LSU Doctoral Dissertations
The drawbacks of active magnetic bearings are arousing interest in the adaptation of mechanical bearings for active use. A promising mechanical bearing candidate for active operation is the tilting-pad bearing. In this research, we introduce an active tilting-pad bearing with linear actuators that translate each pad. The use of feedback in determining the actuator forces allows for the automatic, continuous adjustment of the pad position during the machine operation. In this work, we develop the dynamic model of the active bearing system such that the actuator forces are the control inputs. The hydrodynamic force is modeled as a spring/damper-like force …
Effects Of Strong Surface Energy Anisotropy On Stationary And Migrating Grain-Boundary Grooves, Donghong Min
Effects Of Strong Surface Energy Anisotropy On Stationary And Migrating Grain-Boundary Grooves, Donghong Min
LSU Doctoral Dissertations
Grain-boundary migration controls grain growth and is important in materials processing and synthesis. When a grain boundary ends at a free surface, a groove will develop at the tip to reduce the combined surface and grain-boundary energies. This groove may hinder the grain boundary movement and its effect needs to be understood. Previous studies have solved the groove profile for stationary or migrating grain boundaries by assuming small groove slopes with isotropic surface free energy. This work extends the analysis to finite slopes with isotropic or anisotropic surface free energy.
We first study migrating grain-boundary grooves with isotropic surface energy …
A Slope-Dependent Disjoining Pressure For Lennard-Jones Liquid Films, Taeil Yi
A Slope-Dependent Disjoining Pressure For Lennard-Jones Liquid Films, Taeil Yi
LSU Master's Theses
A molecule in a bulk liquid is subject to intermolecular forces. A molecule in a thin liquid film may experience additional intermolecular forces, if the thin film thickness h is less than roughly 100 nm. The additional forces arise from the molecule's proximity to different materials or phases sandwiching the thin film. The effect of these intermolecular forces at the continuum level is captured by disjoining pressure &Pi. Since dominates at small film thickness, it determines the stability and wettability of thin films. To leading order, Π = Π (h) because thin films are generally uniform. This form, however, can …
Mesoscopic Simulation Of Grain Boundary Diffusion Creep In Inhomogeneous Microstructures, Kanishk Rastogi
Mesoscopic Simulation Of Grain Boundary Diffusion Creep In Inhomogeneous Microstructures, Kanishk Rastogi
LSU Master's Theses
At high temperatures, stresses well below the material’s tensile yield strength can induce permanent deformation over a period of time. This time-dependent progressive deformation of a material at constant stress is called Creep and is observed in both crystalline and non-crystalline solids. The principal deformation processes contributing to creep deformation are slip, sub-grain formation and grain-boundary sliding. Mechanisms involving creep of crystalline materials involve either dislocation motion or diffusional flow of atoms or both. Extensive studies have been done to ascertain the creep mechanism in various regimes of temperature and applied stresses. At low stresses and high temperatures, grain boundary …
Advanced Grid Stiffened Composite Structures, Dinesh Maricherla
Advanced Grid Stiffened Composite Structures, Dinesh Maricherla
LSU Master's Theses
In this study Advanced Grid Stiffened (AGS) composite structures are developed and analyzed for their mechanical properties. It is widely known that these structures possess light weight, high strength, and inherent impact resistance. Because of the advantages mentioned above, the AGS composite structures find many applications in aerospace, ship building and construction industries. The purpose of this study is to manufacture AGS composite structures and analyze AGS composite structures as reinforcement members. A FEA model is also developed and validated with the test results. Parametric analysis is also conducted to investigate the effects of different design parameters on these structures. …
Fracture Toughness Characterization Of Syntactic Foams, Vijay Gorugantu
Fracture Toughness Characterization Of Syntactic Foams, Vijay Gorugantu
LSU Master's Theses
Hollow particle filled polymeric materials called syntactic foams are used as core materials in sandwich composite structures. Syntactic foams find applications in aeronautical and space structures and therefore demand careful study and testing before they can be put to service. In the first part of this thesis work, syntactic foams are fabricated by varying the volume fraction of microballoons and also their density. Four different densities of microballoons are used ranging from 0.22 g/cc to 0.46 g/cc. The volume fraction of the microballoons is varied from 30% to 65%. A set of 3-point bending tests are conducted on these foam …
On The Stability Of Rotor Bearing Systems Based On Hopf Bifurcation Theory, Jianke Wang
On The Stability Of Rotor Bearing Systems Based On Hopf Bifurcation Theory, Jianke Wang
LSU Doctoral Dissertations
This research is aimed to establish instability criteria for a rotor-bearing system which consists of a rotor supported by two fluid-film journal bearings. The static and dynamic characteristics of rotor-bearing systems with consideration of turbulent effects are evaluated by applying the Hopf bifurcation theory (HBT) to the equations of motion. A method is developed for predicting the stability envelope of rotor-bearing systems using HBT. Results are compared with published literature obtained using a trial-and-error method. A method based on HBT is presented for predicting the occurrence of a hysteresis phenomenon, which is observed in experimental results dealing with the instability …
Study Of The Effects Of Magnetic Field On The Properties Of Combustion Synthesized Iron Oxide Nanoparticles, Nagaraju Komuravelli
Study Of The Effects Of Magnetic Field On The Properties Of Combustion Synthesized Iron Oxide Nanoparticles, Nagaraju Komuravelli
LSU Master's Theses
Nanosized chain-like aggregates were developed in an iron pentacarbonyl-carbon monoxide (Fe(CO) 5 ¨C CO) air diffusion flame system. Magnetic field was applied around the diffusion flame using an electromagnet with an intensity of 0.4 Tesla. Transmission Electron Microscopy (TEM) analysis was performed to observe the behavior of the chains formed and to study the effect of magnetic field on these chains. These chain aggregates consist mainly of Fe2O3, which play a vital role in magnetic storage devices. Diffraction pattern analysis and X-ray Photon Spectroscopy (XPS) were carried out to confirm that the chain aggregates consist of mainly ¦Ã-Fe2O3. The effect …
Flow And Temperature Measurements In A Linear Turbine Blade Passage With Leading Edge And Endwall Contouring And With And Without Film Cooling, Ross James Gustafson
Flow And Temperature Measurements In A Linear Turbine Blade Passage With Leading Edge And Endwall Contouring And With And Without Film Cooling, Ross James Gustafson
LSU Master's Theses
Gas turbine efficiency can be improved by increasing the turbine inlet temperature. Secondary flows created in the turbine blade passage cause pressure losses and increase the thermal blade loading on the endwall, thus limiting the combustion temperature. Pressure losses, or aerodynamic losses, extract energy from the fluid, leaving less for torque or thrust production. Secondary flows also cause greater non-uniformity in the exit flow from each blade stage, which decreases the stage efficiency. Weakening secondary flows will lower pressure losses and endwall heat transfer. The following research will explore concepts for weakening the secondary flows through the use of (a) …
Hydrodynamic Analysis Of Compliant Journal Bearings, Amith Hanumappa Reddy
Hydrodynamic Analysis Of Compliant Journal Bearings, Amith Hanumappa Reddy
LSU Master's Theses
Compliant journal bearings are commonly used to support radial loads at extreme operating speeds and conditions where conventional bearings cannot operate. The journal and bearing system are supported by a thin lubricant film (gas) due to the hydrodynamic pressure distribution. To predict the bearing performance parameters, the compressible Reynolds equation is solved based on Infinitely Long Approximation (ILA), Finite Analysis (FA) and a new Modified Parabolic Approximation (MPA). The MPA method reduces the classical Reynolds equation to an ordinary differential equation. Appropriate equations and numerical solution are developed for treating a compressible Reynolds equation using MPA. A series of parametric …
Effects Of Magnetic Field On Micro Flames, Sumathi Swaminathan
Effects Of Magnetic Field On Micro Flames, Sumathi Swaminathan
LSU Master's Theses
The effect of a gradient magnetic field on a diffusion micro flame i.e. C3H8/air flame has been systematically studied to comprehend their interaction. A non-uniform magnetic field was produced in the air gap of an electromagnet and the C3H8/air flame corresponding to various flow velocities was subjected to the non-uniform field. The influence of the operating conditions on the fundamental characteristics of the diffusion flame, such as the flame structure, temperature distribution and the morphology of the soot produced in these flames have been thoroughly investigated. The flame structure and its luminosity were found to be influenced and the flame …
Cryopreservation Of Reproductive Cells And Tissues, Guanglei Li
Cryopreservation Of Reproductive Cells And Tissues, Guanglei Li
LSU Master's Theses
Cryopreservation of reproductive cells and tissues is a useful technique to deliver intact genomes, maximize the distribution of favorable genes, control disease spread. It is widely applied to many fields such as biology, medicine, ecology and agriculture. To optimize the cryopreservation procedure, the biophysical responses of reproductive tissues at different cooling conditions and in different mediums must be clearly understood. Here we studied the biophysical response during freezing of: 1) bovine sperm frozen at a cooling rate of 20 ˚C/min in three media: without cryopreservation agents(CPAs), with 0.7 M glycerol, and with 0.7 M glycerol along with 1.5 mg/ml of …
3-Dimensional Flow Measurements In Square Coaxial Jets, Thomas Lagarde
3-Dimensional Flow Measurements In Square Coaxial Jets, Thomas Lagarde
LSU Master's Theses
Results from un-forced experiments conducted in the three-dimensional flow emanating from coaxial contoured nozzles with square cross section and parallel sides are presented and discussed. Two experiments were conducted with the inner to outer jet nominal velocity ratio equal to l=0.5 and l=1.5. The Reynolds number of the outer jet based on the hydraulic diameter of the outer nozzle exit was in both cases 16,000. A multi-position hot-wire anemometry method was used for measurements in the three-dimensional turbulent flow using a dual film sensor (X-probe). A methodology was developed and implemented to derive the mean-velocity components and Reynolds stresses corrected …
Synthesis And Characterization Of Cobalt-Platinum Thin Films, Priya David
Synthesis And Characterization Of Cobalt-Platinum Thin Films, Priya David
LSU Master's Theses
Co-based alloy thin films have attracted a lot of interest, due to their excellent magnetic properties, that is essential in the field of magnetic recording media. Alloying Co with metals like Pt changes some of its intrinsic magnetic properties such as increasing the magnetocrystalline anisotropy constants of the alloy. Co-Pt thin films and multilayers are more suitable for ultra high-density magnetic recording media because they have high-magnetic anisotropy, chemical stability, excellent coercivity and resistance to corrosion. In the present study, Co-Pt alloy and Pt/Co multilayered films were deposited on Si substrate using dual electron beam co-evaporation. The Co-Pt alloy thin …
Electrodeposited Nanoscale Multilayers Of Invar With Copper, Diwakar Suryanarayana Iyer
Electrodeposited Nanoscale Multilayers Of Invar With Copper, Diwakar Suryanarayana Iyer
LSU Master's Theses
Materials with low thermal expansion coefficients (CTEs) that will survive temperature cycling are of interest in a variety of applications on the microscale, including actuation, precision assembly, and injection mold fabrication. Invar alloys exhibit a low positive coefficient of thermal expansion ranging between 0.2 – 1.2 µm/m-°C at room temperature. The electrodeposition process for fabricating nanoscale multilayers of Invar and copper in micro-patterns was characterized to assess their value in various MEMS applications. In an ongoing effort to maintain a stable CTE and effectively control the grain growth of Invar, nano-multilayers of near Invar-like FeNiCu and copper were electrodeposited into …
Analysis And Testing Of Waste Tire Fiber Modified Concrete, Gregory Marvin Garrick
Analysis And Testing Of Waste Tire Fiber Modified Concrete, Gregory Marvin Garrick
LSU Master's Theses
There are very serious problems with the disposal of waste tires in the United States. Experiments were conducted to determine how the properties of concrete were affected by the inclusion of waste tires. Waste tires were used in the form of chips and fibers. The fibers were further divided into batches with different lengths to determine the effect of length has on the properties of concrete. There was a noticeable decline in the compressive strength of the concrete; however there was an increase in the toughness of the concrete. It was concluded that waste tire fibers were more suitable as …