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Articles 31 - 36 of 36

Full-Text Articles in Engineering

Measurement Of Continuum Breakdown Using A Disc Spin-Down Experiment In Low Pressure Air, Tathagata Acharya Jan 2013

Measurement Of Continuum Breakdown Using A Disc Spin-Down Experiment In Low Pressure Air, Tathagata Acharya

LSU Doctoral Dissertations

As flow becomes rarefied, a quantity called as the tangential momentum accommodation coefficient (TMAC) becomes important because it is a measure of the momentum transport from a gas molecule to a surface. Very few experimental measurements of continuum breakdown in boundary layer flows exist. All experimental measurements of the TMAC in macro-scale boundary layer flows have been done in the continuum slip and the transition flow regimes. Moreover the experimental apparatus used by previous researchers cannot accommodate for materials that are planar by nature such as those used in the field of aerospace and microfabrication. The objectives of this research …


Metal-Based Microchannel Heat Exchangers : Manufacturing And Heat Transfer Testing, Bin Lu Jan 2013

Metal-Based Microchannel Heat Exchangers : Manufacturing And Heat Transfer Testing, Bin Lu

LSU Doctoral Dissertations

This dissertation focuses on improving the functionality of metal-based microchannel heat exchangers (MHEs), as well as pushing this technology toward real-world applications. Design optimization was carried out on MHEs for performance maximization. Double-layered microchannel layout was experimentally studied, and a significant reduction on liquid flow pressure drop penalty was achieved. Other than water, another commonly-used coolant, ethylene glycol, was applied to MHEs, and flow and heat transfer characteristics were quantified. Transient Liquid Phase (TLP) bonding was used for joining Cu structures. For further understanding of the MHE heat transfer, a detailed examination was carried out on the TLP bonding interface …


Modeling, Numerical Analysis, And Predictions For The Detonation Of Multi-Component Energetic Solids, Michael Wayne Crochet Jan 2013

Modeling, Numerical Analysis, And Predictions For The Detonation Of Multi-Component Energetic Solids, Michael Wayne Crochet

LSU Doctoral Dissertations

Metal powders are often used as an additive to conventional high explosives to enhance the post-detonation blast wave. Piston-impact simulations are commonly utilized to predict performance metrics such as detonation speed and strength, as well as assessing the impact and shock sensitivity of these materials. The system response is strongly influenced by the initial particle size distribution and material composition. Multiphase continuum models have been routinely applied at the macroscale to characterize the detonation of solid high explosives over engineering length scales. Current models lack a description of the physically permissible constitutive relations for mass transfer due to general chemical …


Analysis And Optimization Of Film Cooling Effectiveness, Hessam Babaee Jan 2013

Analysis And Optimization Of Film Cooling Effectiveness, Hessam Babaee

LSU Doctoral Dissertations

In the first part, an optimization strategy is described that combines high-fidelity simu- lations with response surface construction, and is applied to pulsed film cooling for turbine blades. The response surface is constructed for the film cooling effectiveness as a function of duty cycle, in the range of DC between 0.05 and 1, and pulsation frequency St in the range of 0.2-2, using a pseudo-spectral projection method. The jet is fully modulated and the blowing ratio, when the jet is on, is 1.5 in all cases. Overall 73 direct numerical sim- ulations (DNS) using spectral element method were performed to …


Fabrication And Characterization Of A Polymeric Nanofluidic Device For Dna Analysis, Jiahao Wu Jan 2013

Fabrication And Characterization Of A Polymeric Nanofluidic Device For Dna Analysis, Jiahao Wu

LSU Doctoral Dissertations

The growing needs for cheaper and faster sequencing of long biopolymers such as DNA and RNA have prompted the development of new technologies. Among the novel techniques for analyzing these biopolymers, an approach using nanochannel based fluidic devices is attractive because it is a label-free, amplification-free, single-molecule method that can be scaled for high-throughput analysis. Despite recent demonstrations of nanochannel based fluidic devices for analyzing physical properties of such biopolymers, most of the devices have been fabricated in inorganic materials such as silicon, silicon nitride and glass using expensive high end nanofabrication techniques such as focused ion beam and electron …


Developing Defect-Tolerant Demolding Process In Nanoimprint Lithography, Alborz Amirsadeghi Jan 2013

Developing Defect-Tolerant Demolding Process In Nanoimprint Lithography, Alborz Amirsadeghi

LSU Doctoral Dissertations

Demolding, the process to separate stamp from molded resist, is most critical to the success of ultraviolet nanoimprint lithography (UV-NIL). In the present study we first investigated adhesion and demolding force in UV-NIL for different compositions of a model UV-curable resist containing a base (either tripropyleneglycol diacrylate with shorter chain length or polypropyleneglycol diacrylate with longer chain length), a cross-linking agent (trimethylolpropane triacrylate) and a photoinitiator (Irgacure 651). The demolding force was measured using a tensile test machine after imprinting the UV resist on a silicon stamp. In general, the shorter monomer shows a larger demolding force. Decreasing the cross-linking …