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Full-Text Articles in Engineering
Quantification Of Mitral Regurgitation With Mr Phase-Velocity Mapping Using A Control Volume Method, George P. Chatzimavroudis, John N. Oshinski, Roderic I. Pettigrew, Peter G. Walker, Robert H. Franch, Ajit P. Yoganathan
Quantification Of Mitral Regurgitation With Mr Phase-Velocity Mapping Using A Control Volume Method, George P. Chatzimavroudis, John N. Oshinski, Roderic I. Pettigrew, Peter G. Walker, Robert H. Franch, Ajit P. Yoganathan
Chemical & Biomedical Engineering Faculty Publications
Reliable diagnosis and quantification of mitral regurgitation are important for patient management and for optimizing the time for surgery. Previous methods have often provided suboptimal results. The aim of this in vitro study was to evaluate MR phase-velocity mapping in quantifying the mitral regurgitant volume (MRV) using a control volume (CV) method. A number of contiguous slices were acquired with all three velocity components measured. A CV was then selected, encompassing the regurgitant orifice. Mass conservation dictates that the net inflow into the CV should be equal to the regurgitant flow. Results showed that a CV, the boundary voxels of …
Strength Degradation Of Sapphire Fibers During Pressure Casting Of A Sapphire-Reinforced Ni-Base Superalloy, R. Asthana, Surendra N. Tewari, S. L. Draper
Strength Degradation Of Sapphire Fibers During Pressure Casting Of A Sapphire-Reinforced Ni-Base Superalloy, R. Asthana, Surendra N. Tewari, S. L. Draper
Chemical & Biomedical Engineering Faculty Publications
Transient-liquid-phase (TLP) bonding was used to fabricate a Haynes 230 Ni-base superalloy/sapphire fiber composite for high-temperature applications. Boron was used as a melting-point depressant for the Ni, to aid superalloy infiltration of the fibers. Preliminary study of the composite indicated an incomplete TLP bonding cycle. Therefore, microstructural and microchemical analyses were carried out to determine the TLP bonding mechanism. It was found that the TLP process did not occur under local thermodynamic equilibrium conditions at the solid/liquid interfaces, contrary to the primary assumption of conventional models, so a modified model for TLP bonding is proposed. The main differences between the …
Diffusivities Of N-Alkanes In Silicalite By Steady-State Single-Crystal Membrane Technique, Orhan Talu, Matthew S. Sun, Dhananjai B. Shah
Diffusivities Of N-Alkanes In Silicalite By Steady-State Single-Crystal Membrane Technique, Orhan Talu, Matthew S. Sun, Dhananjai B. Shah
Chemical & Biomedical Engineering Faculty Publications
A novel experimental technique that measures the diffusive flux through a single-crystal membrane (SCM) was developed and tested. Unlike all other macroscopic techniques that depend on a transient response, SCM is used under steady-state conditions, which results in a wide range of applicability from 10−2 to 10−11 cm2/s. Phenomenological equations for the steady-state data analysis were developed. The variation of driving force over the diffusion path is included in the model. As required by thermodynamics, the micropore concentration is given as a function of surface-excess amount adsorbed and gas density. The membrane configuration measures diffusivity in …
Dynamic Analysis Of Unidirectional Pressure Infiltration Of Porous Preforms By Pure Metals, Dhiman K. Biswas, Jorge E. Gatica, Surendra N. Tewari
Dynamic Analysis Of Unidirectional Pressure Infiltration Of Porous Preforms By Pure Metals, Dhiman K. Biswas, Jorge E. Gatica, Surendra N. Tewari
Chemical & Biomedical Engineering Faculty Publications
Unidirectional pressure infiltration of porous preforms by molten metals is investigated numerically. A phenomenological model to describe fluid flow and transport phenomena during infiltration of fibrous preforms by a metal is formulated. The model describes the dynamics of the infiltration process, the temperature distribution, and solid fraction distribution. The numerical results are compared against classical asymptotic analyses and experimental results. This comparison shows that end effects may become important and render asymptotic results unreliable for realistic samples. Fiber volume fraction and initial temperature appear as the factors most strongly influencing infiltration. Metal superheating affects not only the length of the …