• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1999.11a
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• pp.71-74
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• 1999

농업ㆍ원예분야에서 다공질 재료를 인공배지로 이용하기 위하여는 수분관리의 용이성, 우수한 양분의 유지, 통기성 및 보수성이 요구된다. 이들 성질을 만족시키는 재료로는 점토, 벤토나이트, 질석(vermicutite), 펄라이트(perlite) 및 락-울(rock-wool) 등이 이용된다. 인공배지 재료로 널리 사용되는 펄라이트와 락-울의 원료는 중국 및 호주 등지로부터 수입에 의존하고 있어 양액재배 농가에 커다란 부담이 되며 건습조절이 곤란하여 배지 내 수분함량의 조절이 용이하고 양액사용이 간편한 배지 및 폐기처리시 환경문제를 야기하지 않는 반영구적이며 자연친화형의 배지의 개발이 절실히 요구되고 있다. (중략)

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.89-95
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• 1999

The compression behavior of semi-solid materials in studied from a viewpoint of yield criteria and analysis methods. To describe the behavior of materials in semi-solid state, several theories have been proposed by extending the concept of plasticity of porous compressible materials. in the present work, the upper-bound method and the finite element method are used to model the simple compression process using yield criteria of Kuhn and Doraivelu. Segregation between solid and liquid which cause defect of product is analysed for Sn-15%Pb alloy is compared with the experimental result of Charreyron et al..

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.12
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• pp.3715-3727
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• 1996

Compression behavior of semi-solid aluminum alloys with controlled solid fractions was investigated in the present study. The stress and strain relationships were obtained from the compression test. Variations of the solid fraction distribution and the material behaviour were investigated for various friction coeffieiants and die speedsd. For a finite element analysis, the semi-solid material was described by a compressible regid viscoplastic model for the solid region and darcy's law for the liquid region. The computed results were compared with experimental data for the validity of the yield criteria.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.235-240
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• 2010

Transpiration cooling is the most effective cooling technique for liquid rocket and air-breathing engines operating in aggressive environments with higher pressures and temperatures. Combustor liners and turbine vanes are cooled by the coolant(air or fuel) passing through their porous walls and also the exit coolant acting as an insulating film. However, its practical implementation has been hampered by the limitations of available porous materials. The search for more practical methods of increasing the internal heat transfer within the walls has led to the development of multi-laminate porous structures, such as Lamilloy$^{(R)}$ and Transply$^{(R)}$. This paper reviews recent research activities of transpiration cooling for the propulsions of liquid rocket, gas turbine, and scramjet.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.8
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• pp.560-564
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• 2003

Thick oxide layer was fabricated by anodic reaction and complex oxidation performed by combining low temperature thermal oxidation (50$0^{\circ}C$, 1 hr at $H_2O$/O$_2$) and a RTO (rapid thermal oxidation) process (105$0^{\circ}C$, 1 min). Electrical characteristics of OPSL (oxidized porous silicon layer) were almost the same as those of thermal silicon dioxide prepared at high temperature. The leakage current through the OPSL of 20${\mu}{\textrm}{m}$ thickness was about 100 - 500 ㎀ in the range 0 V to 50 V. The average value of breakdown field was about 3.9 MV/cm. From the XPS analysis, surface and internal oxide films of OPSL prepared by complex process were confirmed completely oxidized and also the role of RTO process was important for the densification of PSL (porous silicon layer) oxidized at low temperature.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.03a
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• pp.1-23
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• 1996

투과증발(Pervaporation)이란 어원적으로 "permeation"과 "evaporation"의 합성어인데 액체혼합물이 치밀한 비다공질막을 통해 이동하는 동안 증기화되면서 분리되는 막분리 공정이다. 이 공정에서 막 한쪽면은 액체공급액과 접하고 있고 다른 한쪽면은 낮은 투과물의 증기압과 접하고 있는데 낮은 증기압은 진공(vacuum pervaporation)을 가하거나 혹은 불활성의 담체가스(sweep gas pervaporation)를 흐르게 하므로써 얻을 수 있다. 이때 막 내부에 트과증발막공정의 추진력인 화학 포텐셜(chemical potential) 구배가 발생하여 막을 통한 물질투과가 이루어지는데 각 투과성분의 투과속도는 투과성분과 막재료간의 물리화학적 인력에 의해 결정된다.의 물리화학적 인력에 의해 결정된다.

• Journal of the Korean Geosynthetics Society
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• v.7 no.2
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• pp.23-29
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• 2008

The purpose of this research is to assess the application of recycled-aggregate that is gained from construction wastes as the material of compaction pile method. At the same time, the development of the new technique rectifies defects of the existing compaction pile method for soft ground improvement. In this research, laboratory chamber tests were carried out analyzing the effect of the soft ground improvement by porous concrete pile using recycled aggregate. Through the results of the laboratory chamber tests, the variations of settlement, excess pore pressure, and increment of the vertical stress with time and the behavior of the composite ground were elucidated.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.75-83
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• 2011

Emerging issues related with fully coupled Thermo-Hydro-Mechanical (THM) behavior of unsaturated soil demand the development of a numerical tool in diverse geo-mechanical and geo-environmental areas. This paper presents general governing equations for coupled THM processes in unsaturated porous media. Coupled partial differential equations are derived from three mass balances equations (solid, water, and air), energy balance equation, and force equilibrium equation. With Galerkin formulation and time integration of these governing equations, finite element code is developed to find nonlinear solution of four main variables (displacement-u, gas pressure-$P_g$), liquid pressure-$P_1$), and temperature-T) using Newton's iterative scheme. Three cases of numerical simulations are conducted and discussed: one-dimensional drainage experiments (u-$P_g-P_1$), thermal consolidation (u-$P_1$-T), and effect of pile on surrounding soil due to surface temperature variation (u-$P_1$-T).

• Journal of the Korean Geotechnical Society
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• v.30 no.9
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• pp.67-75
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• 2014

Methane gas hydrate which is considered energy source for the next generation has an urgent need to develop reliable numerical simulator for coupled THM phenomena in the porous media, to minimize problems arising during the production and optimize production procedures. International collaborations to improve previous numerical codes are in progress, but they still have mismatch in the predicted value and unstable convergence. In this paper, FEM code for fully coupled THM phenomena is developed to analyze methane hydrate dissociation in the porous media. Coupled partial differential equations are derived from four mass balance equations (methane hydrate, soil, water, and hydrate gas), energy balance equation, and force equilibrium equation. Five main variables (displacement, gas saturation, fluid pressure, temperature, and hydrate saturation) are chosen to give higher numerical convergence through trial combinations of variables, and they can analyze the whole region of a phase change in hydrate bearing porous media. The kinetic model is used to predict dissociation of methane hydrate. Developed THM FEM code is applied to the comparative study on a Masuda's laboratory experiment for the hydrate production, and verified for the stability and convergence.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.447-455
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• 2013

A micro-mechanical pipe network model with the shape of a cube was developed to simulate the behavior of fluid flow through a porous medium. The fluid-flow mechanism through the cubic pipe network channels was defined mainly by introducing a well-known percolation theory (Stauffer and Aharony, 1994). A non-uniform flow generally appeared because all of the pipe diameters were allocated individually in a stochastic manner based on a given pore-size distribution curve and porosity. Fluid was supplied to one surface of the pipe network under a certain driving pressure head and allowed to percolate through the pipe networks. A percolation condition defined by capillary pressure with respect to each pipe diameter was applied first to all of the network pipes. That is, depending on pipe diameter, the fluid may or may not penetrate a specific pipe. Once pore pressures had reached equilibrium and steady-state flow had been attained throughout the network system, Darcy's law was used to compute the resultant permeability. This study investigated the sensitivity of network size to permeability calculations in order to find out the optimum network size which would be used for all the network modelling in this study. Mean pore size and pore size distribution curve obtained from field are used to define each of pipe sizes as being representative of actual oil sites. The calculated and measured permeabilities are in good agreement.