• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.226-233
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• 1999

An experimental study has been performed on natural convection heat transfer with a rapid crust formation in the molten metal pool of a low Prandtl number fluid. Two types of steady state tests, a low and high geometric aspect ratio cases in the molten metal pool, were performed. The crust thickness by solidification was measured 88 a function of boundary surface temperatures. The experimental results on the relationship between the Nusselt number and Rayleigh number In the molten metal pool with a crust formation were compared with existing correlations. The experimental study has shown that the bottom surface temperature of the molten metal layer, in all experiments. is the major influential parameter in the crust formation, duo to the natural convection flow. The Nusselt number of the case without a crust formation in the molten metal pool is greater than that of the case with the crust formation at the same Rayleigh number. The present experimental results on the relationship between the Nusselt number and Rayleigh number In the molten metal pool match well with Globe and Dropkin's correlation. From the experimental results, a now correlation between the Nusslet number and Rayleigh number in the molten metal pool with the crust formation was developed as $Nu=0.0923(Ra)^{0.302}$ ($2{\times}10^4< Ra<2{\times}10^7$).

• Proceedings of the Petrological Society of Korea Conference
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• 2000.05a
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• pp.86-86
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• 2000

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.49-55
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• 2001

본 논문에서는 서해안 폐기물 매립지 하부의 점성토와 고화차수재를 재료로 수행된 확산시험 결과와 현장 조건을 적용하여 오염물이동성에 대한 수치해석을 수행하였다. 무기화합물이 하부 차수재와 원지반퇴적층으로 이동되는 일차원 이동 특성을 대상으로 하였으며 일차원 용질이동해석 프로그램 CDFD(convection-dispersion finite difference)를 현장의 비균질한 지층에 이용할 수 있도록 수정하여 적용하였다. 그 결과 원지반점성토를 통한 용질이동 메카니즘에 확산이 기여하는 정도가 50%로 매우 큰 영향을 갖고 있음을 보여주며 원지반 투수계수가 클수록 인공차수층의 필요성이 증대됨을 알 수 있었다.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.391-396
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• 2006

When radioactive wastewater was solidified treatment by cement, the drying rate of cement and the volume reduction ratio was decreased because of boric acid component in the wastewater. In order to supplement the demerit, effects of paraffin wax investigated in this study. Paraffin wax has a hydrophobic properties and a low affinity with inorganic materials. When the radioactive wastewater was tested by a small of wax, the compressive strength of solidified waste are decreased Therefore boric acid in radioactive wastewater are first treated by alkali salt and coated by the stearic acid. During the solidification step, The amount of paraffin wax addition get the result that the compressive strength of solidification with cement was the same as that with paraffin wax. The leaching properties of radioactive waste solidified was the same CFL (cumulative fraction leached), PR (penetration rate), effective diffusivity if paraffin wax content in solidified waste was 20% or 25%.

• Economic and Environmental Geology
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• v.39 no.2 s.177
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• pp.191-212
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• 2006

Placer gold deposits is mainly distributed in the Takaoi area. The alluvium is unconsolidated or semiconsolidated deposit consisting of gravel, sand, and soil beds in ascending order. They unconformably overlies the Carboniferous-Permian schist and Cretaceous granodiorite substratum. Based on detailed facies analysis, the alluvium can be interpreted as a typical fluvial deposits containing gravel and sand beds of channel-fill unit and soil deposit of floodplain. Gold grains are included mainly in the gravel bed and vein quartz is only contained gold among all kinds of gravels. These features indicates that the source rock of the gold grain is vein quartz and gold grains are separated from vein quartz during transport and abrasion. The reserves of gold in this area reach to at least 792 kg.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.707-712
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• 1996

중대사고시 원자로 압력용기내 또는 원자로 공동(cavity) 내에서의 노심용융물은 주입되는 물로 인하여 물과 접촉하는 표면이 냉각되면서 피막층(crust)이 형성된다. 이러한 피막층의 형성은 노심용융물과 냉각수 사이의 열전달 현상에 영향을 미치며 중대사고 발생시 사고 진행에 중요한 역할을 한다. 본 연구에서는 이러한 용융물의 피막층 형성의 해석모델을 수립하기 위해 전이현상과 전도와 대류를 포함하는 2차원 열전달과 상변화를 수반하는 문제를 포함하는 운동량방정식과 에너지방정식을 2차원으로 구성하였으며 에너지방정식은 엔탈피의 함수로 나타내었다. 그리고 이러한 2차원 지배방정식을 해석하기 위해 유한차분법 및 SIMPIER 알고리즘을 이용하였다. 비교대상으로는 한국원자력연구소에서 수행한 냉각수의 비등과 기체주입 효과가 고려되지 않은 실험을 대상으로 하였다. 계산결과 용융물의 피막층은 파동(wave) 형태로 형성되었으며 일정시간이 경과하면 변화가 없는 안정한 상태가 되었다. 용융물 내에서의 온도분포는 액체상태일 경우에는 하부가열면과 상변화가 일어나는 경계면부근을 제외하고는 거의 일정한 온도분포를 나타내고 있으며 용융물이 고화된 피막층에서는 급격한 온도변화를 보여주고 있다.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.03a
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• pp.147-152
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• 1997

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.245-253
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• 2017

Vietnam CFBC fly ash has high CaO content and can be used as a solidification agent for soft ground improvement. However, most fly ash is treated as landfill or waste. In order to utilize fly ash as a solidification agent for soil improvement, the characteristics of fly ash must be accurately determined. In this study, laboratory tests were conducted on fly ash from four CFBC power plants to evaluate the utility of Vietnam fly ash as a solidification agent. As a result of analyzing the physical properties, it was analyzed that all four samples were suitable as material for solidification agent and have suitable particle size for the improvement of soft ground. As a result of analysis of chemical characteristics, it was analyzed that the fly ash of one place could be used as a solidification agent because of the high content of free-CaO. The remaining three fly ash was not suitable for use as a solidification agent due to low Free-CaO content. However, it has a chemical composition similar to that of general fly ash in Korea, so it can be recycled in various ways.

• Journal of the Korean GEO-environmental Society
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• v.8 no.1
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• pp.13-20
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• 2007

Leachates resulting from the waste landfill of waste can possibly cause the second pollution, such as the underground water and environmental pollution. Accordingly, Liner layer has been installed in the reclaimed land of waste to block and purify permeation water to and prevent this second pollution. The material used as Liner layer should have water resistance and be less than permeability coefficient of $1{\times}10^{-7}$ cm/sec. As it is very difficult to get this kind of natural clay with low permeability around the field, the suitable way to get the low permeable material is to use blend with good watertighness by mixing it with natural soil which is spread in the site. While this mixed soil, which can resist water, is commonly used in the site, namely, bentonite and MCG cementious mateiral mixed soil, which is widely used as Liner layer in the reclaimed land of waste, is recognized in Liner and durability. The study was performed to find the effect of additive of the bottom liner in the waste landfill. The aim of this paper is to explain of the field application examples as well as the data of experimental research with the engineering properties of Liner layer of the reclaimed land.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.2
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• pp.64-72
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• 2001

Weld line is one of serious troubles which are observed in a plastic part manufactured by a injection molding process. This is caused by many process factors, which are molding pressure, temperature, velocity, location of a injection gate, mold geometry and material properties. investigation on the effects of these process factors to the appearance of a weld line was carried out using a finite element method. Filling and packing analyses were carried out by modifying both the configuration of the injection gates and cavity thickness. Proper locations of the injection gates could be determined by considering molding pressure, temperature, velocity and frozen layer, and whereby the weld line was controled. In order to make a weak appearance of the weld line, flow velocity and flow front in a cavity were also investigated by modifying a cavity thickness. As a result, flow front was extended around the corner in the cavity by changing the flow velocity and hence the appearance of the weld line was much weakened.