• Nuclear Engineering and Technology
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• 제42권6호
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• pp.620-635
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• 2010

In this paper we describe current activities on the project Multi-Scale Modeling and Analysis of convective boiling (MSMA), conducted jointly by the Paul Scherrer Institute (PSI) and the Swiss Nuclear Utilities (Swissnuclear). The long-term aim of the MSMA project is to formulate improved closure laws for Computational Fluid Dynamics (CFD) simulations for prediction of convective boiling and eventually of the Critical Heat Flux (CHF). As boiling is controlled by the competition of numerous phenomena at various length and time scales, a multi-scale approach is employed to tackle the problem at different scales. In the MSMA project, the scales on which we focus range from the CFD scale (macro-scale), bubble size scale (meso-scale), liquid micro-layer and triple interline scale (micro-scale), and molecular scale (nano-scale). The current focus of the project is on micro- and meso-scales modeling. The numerical framework comprises a highly efficient, parallel DNS solver, the PSI-BOIL code. The code has incorporated an Immersed Boundary Method (IBM) to tackle complex geometries. For simulation of meso-scales (bubbles), we use the Constrained Interpolation Profile method: Conservative Semi-Lagrangian $2^{nd}$ order (CIP-CSL2). The phase change is described either by applying conventional jump conditions at the interface, or by using the Phase Field (PF) approach. In this work, we present selected results for flows in complex geometry using the IBM, selected bubbly flow simulations using the CIP-CSL2 method and results for phase change using the PF approach. In the subsequent stage of the project, the importance of effects of nano-scale processes on the global boiling heat transfer will be evaluated. To validate the models, more experimental information will be needed in the future, so it is expected that the MSMA project will become the seed for a long-term, combined theoretical and experimental program.

• Journal of Preventive Medicine and Public Health
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• 제2권1호
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• pp.61-76
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• 1969

A review has been made of mortality trends in Korea from 1958 to 1967 analyzing the data by sex, age and cause of death. The crude death rates and age specific death rates were estimated by the model of N. Keyfitz life table which had been developed by the data of the 1960's national census. The cause specific death rates shown in this article are based on the following: all deaths occurring in the death-registration are expressed as a numberator, while the denominator was estimated from the regular national census data by interpolation method. It is estimated that only an average of about 40% of deaths which occurred during a year were registered during 1958 to 1967. The validity and the reliability of the diagnosis of causes of death seem to be extremely poor in this country. Therefore the cause specific death rates in this article are aimed to reveal trends of causes of registered death ana not for the actual level of death rates. For 10 years very interesing mortality trends were observed : 1. The trend in the crude death rates was downward slowly. 2. The estimated death rate for the infant in 1960 was still high up to 100 per 1,000. 3. The rates for mortality attributed to such infectious diseases as pneumonia, bronchitis, gastroenteritis and measles decreased an average 40-60%. 4. The death rates for over-all tuberculosis decreased only 9.8%. 90% of the decrease was contributed by those in the less-than-15 year age group. 5. The death rates for chronic diseases, such as vascular diseases affecting the central nervous system, malignant neoplasm, major heart diseases and all accidents rose about 40-60%. 6. The rank order of the 10 leading causes of death showed large changes over the years, except for pneumonia and tuberculosis which occupyed 1st and 2nd places respectively. Vascular diseases affecting the central nervous system moved from 5th to 3rd place and malignant neoplasm from 6th to 4th place, The major heart diseases moved from 10th to 6th place and all accidents from 10th to 7th place. On tile other hand, gastroenteritis moved from 3rd to 5th place and influenja from 4th to 8th place.