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Theory Of Curvature-Dependent Disjoining Pressure And Its Application To Liquid Films, Jin Zhang Jan 2006

Theory Of Curvature-Dependent Disjoining Pressure And Its Application To Liquid Films, Jin Zhang

LSU Doctoral Dissertations

A liquid film of thickness h < 100 nm is subject to additional intermolecular forces, which are collectively called disjoining pressure Pi. Since Pi dominates at small film thicknesses, it determines the stability and wettability of thin films. Current theory for uniform films gives Pi = Pi(h). It becomes unbounded as h -> 0. We present a theory of curvature-dependent disjoining pressure. The new Pi depends on the curvature hxx, slope hx, and h. When this theory is implemented for Lennard-Jones liquid films, the new Pi is bounded as h -> 0. We show that this Pi captures three regimes of drop behavior (complete wetting, partial wetting, and pseudo partial wetting) without altering the signs of the long and short-range interactions. We also find that a drop with a uniform film is linearly stable, whereas a drop without a uniform film is unstable. Evaporating thin films is important ...


Uv-Liga Micro-Fabrication Of Inertia Type Electrostatic Transducers And Their Application, Seok Jae Jeong Jan 2006

Uv-Liga Micro-Fabrication Of Inertia Type Electrostatic Transducers And Their Application, Seok Jae Jeong

LSU Doctoral Dissertations

This dissertation discusses the design, working principles, static & dynamic analysis and simulation, mechanics of material, applied MEMS technology, micro-fabrication, and experimental testing of two types of micro-transducers: micro-power relay and micro-accelerometer. Several possible design concepts were proposed, and the advantages and disadvantages of electrostatic working principles were also discussed. Transducers presented in this research used electrostatic force as a driving force in the micro-relay and capacitance as a sensing parameter in the micro-accelerometer. There was an analogy between the micro-relay and the micro-accelerometer in their theoretical approach and fabrication processes. The proposed micro-transducers (micro-relay and micro-accelerometer) were fabricated using UV ...


System Optimization For Realizing A Miniaturized Gas Chromatograph Sensor For Rapid Chemical Analysis, Abhinav Bhushan Jan 2006

System Optimization For Realizing A Miniaturized Gas Chromatograph Sensor For Rapid Chemical Analysis, Abhinav Bhushan

LSU Doctoral Dissertations

Rapid and comprehensive on-site analysis of chemicals in applications ranging from industrial process control to homeland security is of significant importance to improve the environment and save human life. The need for sensors that are fast, reliable, and portable has never been greater. For the challenging task of on-site instrumentation, where power sources can be limited, shrinking the size of the device is the most effective way to conserve power. Although gas chromatography is a mature technique well suited for these applications, current instrumentation has deficiencies that limit its usage. Speed of analysis and non portability are severe hindrances to ...


Active Control Of Spray Combustion, Onur Tuncer Jan 2006

Active Control Of Spray Combustion, Onur Tuncer

LSU Doctoral Dissertations

Effect of a forced dilution air jet on air-fuel spray mixing and emissions has been investigated. Temperature measurements have been made at a number of forcing frequencies in the range of 100-1100 Hz and blowing ratios between 6-15. Open-loop flame response to forcing has also been acquired by recording pressure and heat release spectra. The results show that the mean temperature field inside the flame can be altered due to jet modulation. Significant effects are observed by forcing at locations close to the dump plane. Enhancements in temperature of the order of 100–200 ˚C, and reduction in pattern factor ...


Tribological Aspects Of Journal Bearings Focusing On The Stribeck Curve, Xiaobin Lu Jan 2006

Tribological Aspects Of Journal Bearings Focusing On The Stribeck Curve, Xiaobin Lu

LSU Doctoral Dissertations

The dissertation focuses on the frictional characteristics of journal bearings as represented by the Stribeck curve. The behavior of lift-off speed and the factors that affect it are explored. An equation is proposed for predicting the lift-off speed. The comparison between the experimental results of oil- and grease-lubricated journal bearings with a mixed elastohydrodynamic lubrication model for line contacts is indicative of good agreement in the mixed lubrication regime. Efforts are made to modify the surface profile of bushing by putting dimples on its surface. Experimental results show that with proper dimensions of dimples, the friction performance of journal bearings ...