Microstructural evolution and control in the directional solidification of Fe-C-Si alloys

The main objective of this study was to examine the influence of four impurities S, Te, O, and H on structure control in the directional solidification of Fe-C-Si alloys. In the course of the solidification experiments, it was also observed that control of the solidification atmosphere by either H[subscript]2 or O[subscript]2 gas had a substantial influence on the microstructure. Both the S and H had similar effects on the gray solidification. Their effects were demonstrated by coarsening of the type A flake graphite structures and also by the promotion of the type A growth at higher velocities, compared to the results obtained from the solidification of high purity alloys under pure Ar atmosphere. The S effect was different from the H effect in that the former induced fine type D undercooled graphite and the latter coral graphite when the type A growth was terminated upon increasing the solidification velocity. In contrast to the S and H, it was found that the O suppressed the type A growth in high purity alloys, which was replaced by the growth of coral graphite at an extremely low solidification rate;The Auger analysis in Part II showed that the iron matrix/graphite interface regions were contaminated by the adsorbed elements S or O when the graphite solidified in flake morphology, type A or D, in both high purity and S-added alloys. The O presence was, however, observed only in coarse type A structure. The experiments in Part III produced evidence supporting that both the type A and D graphite grow by the extension of basal growth layers. Part IV of this study produced evidence that the interaction of the H with Te, as opposed to independent action of H, is primarily responsible for the enhancement of Te effectiveness in promoting white iron growth. The experimental results of the present study lead to the conclusion that the presence of impurity elements, either by doping addition (S and Te) or by atmosphere control (H and O), controls the structure of cast iron through the adsorption at the growth front (S and Te) or through the interaction with O (H). (Abstract shortened with permission of author.

Layer-by-Layer Assembly of Clay-filled Polymer Nanocomposite Thin Films

A variety of functional thin films can be produced using the layer-by-layer assembly technique. In this work, assemblies of anionic clay and cationic polymer were studied with regard to film growth and gas barrier properties. A simple, yet flexible robotic dipping system, for the preparation of these thin films, was built. The robot alternately dips a substrate into aqueous mixtures with rinsing and drying in between. Thin films of sodium montmorillonite clay and cationic polymer were grown and studied on poly(ethylene terephthalate) film or a silicon wafer. After 30 clay polymer bilayers were deposited, the resulting transparent film had an oxygen transmission rate (OTR) below 0.005 cm3/m2/day/atm. This low OTR, which is unprecedented for a clay-filled polymer composite, is believed to be due to a ?brick wall? nanostructure comprised of completely exfoliated clay bricks in polymeric ?mortar?. The growth of polymer and clay assemblies is then shown to be controlled by altering the pH of polyethylenimine (PEI). Growth, oxygen permeability, and mechanical behavior of clay-PEI assemblies were studied as a function of pH in an effort to tailor the behavior of these thin films. Thicker deposition at high pH resulted in reduced oxygen permeability and lower modulus, which highlights the tailorability of this system

ワークショップ報告 仏画「甘露幀」にみる民俗演戯の諸相

ワークショップ報告 第1班公開研究会 「図像から読み解く東アジアの生活文化

A spectral element formulation for fluid-structure interactions : applications to flow through collapsible channels

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996.Includes bibliographical references (leaves [126]-130).by James Jang-Sik Shin.Ph.D

Numerical modeling of forced expiratory flow in a human lung

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992.Includes bibliographical references (leaves 77-81).by James Jang-Sik Shin.M.S

Impact assessment of CO2 mitigation options in Korea using energy system analysis model

AbstractThe Korea Electric Power Research Institute (KEPRI) has performed a study to analyze the deployment impact of CO2 mitigation options in the power generation sector in Korea, with IEA Clean Coal Centre. The goal of this study is the identification of the viable technology and legal options for CO2 mitigation, and the impact assessment of the options for the Korean power generation sector.The MARKAL modeling package of IEA/ETSAP was used as an appropriate tool to make the database of Korean energy system in the model and assess the effects of the options. Several scenarios were made to study the effect of CO2 emission reductions on the Korean power generation sector, and these were classified as the Base Scenario, New Technology Scenario, Carbon Tax Scenario, Total Carbon Emission Cap Scenario, and mixtures of the scenarios.Under the base scenario based on the National Electricity Plan of Korea, the future power generation will be dominated by nuclear and coal power plants, with some of natural gas fired plant and a very small proportion of renewables. However, with increasing pressure to mitigate CO2 emissions, the analysis results of all four scenarios and combination of the scenarios showed that Korea would have to adopt a little different approach. An extensive modeling work was, therefore, undertaken to analyze the impact of various measures on introduction of new technologies and policies in order to achieve significant CO2 emissions reduction. As results of this work, we found estimated average cost for a ton carbon mitigation and estimated amount of CO2 emission reduction by application of each scenario including constraint of lower limit of coal power generation for security of energy supplies in Korea. The results obtained are to be suggested as recommendation in establishing a sustainable energy portfolio within the Korean power generation sector