• 한국컴퓨터정보학회논문지
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• 제29권6호
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• pp.23-29
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• 2024

본 논문에서는 옷감과 입자 기반 유체 해법인 SPH(Smoothed particle hydrodynamics)를 이용한 액체 간의 상호작용으로 표현되는 다공성 흐름(Pore flow), 흡수, 방출 그리고 확산 효과를 GPU 기반으로 빠르게 표현할 수 있는 방법을 제안한다: 1) 옷감-액체의 상호작용에 의해 표현되는 다양한 물리적 효과를 GPU 기반으로 표현할 수 있는 통합형 프레임워크, 2) SPH 기반으로 노드의 포화도를 효율적으로 계산하고 이를 주변 Porous 입자들로 전달하는 방법, 3) 유체 흡수 및 방출 방향을 안정적으로 계산하기 위해 다르시 법칙(Darcy's law)을 기반으로 안정성을 개선시키는 방법, 4) Porous 입자들로 흡수되는 과정에서 유체의 흐름 방향에 따라 흡수되는 양을 조절하는 방법, 마지막으로 5) SPH 입자의 최대 질량이 넘지 않도록 방출할 수 있는 방법을 제시한다. 제안하는 방식의 가장 큰 장점은 모든 연산이 GPU에서 계산되고 동작하기 때문에 빠르게 옷감과 유체의 상호작용으로 표현되는 다공성 재질, 다공성 흐름, 흡수, 반사, 확산 등을 모델링할 수 있다.

• Membrane and Water Treatment
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• 제4권2호
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• pp.143-155
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• 2013

Four membranes were used to separate Chlorella sp. from their culture medium in cross-flow microfiltration (MF) experiments: cellulose acetate (CA), cellulose nitrate (CN), polypropylene (PP) and polyvinylidenefluoride (PVDF). It was found that the hydrophilic CA and CN membranes with a pore size of 1.2 ${\mu}m$ exhibited the best performances among all the membranes in terms of permeation flux. The hydrophobicity of each membrane material was determined by measuring the angle between the water (liquid) and membrane (solid). Contact angle measurements showed that deionized (DI) water had almost adsorbed onto the surfaces of the CA and CN membranes, which gave $0.00^{\circ}$ contact angle values. The PP and PVDF membranes were more hydrophobic, giving contact angle values of $95.97^{\circ}$ and $126.63^{\circ}$, respectively. Although the pure water flux increased with increasing pore diameter (0.8 < 1.2 < 3.0 ${\mu}m$) in hydrophilic CA and CN membranes, the best performance in term of filtration rate for filtering a microalgae suspension was attained by membranes with a pore size of 1.2 ${\mu}m$. The fouled membrane pore sizes and pore blocking were inspected using a scanning electron microscope (SEM). MF with large pore diameters was more sensitive to fouling that contributed to intermediate blocking, where the size of the membrane pores is almost equivalent to that of cells.

• Ocean Science Journal
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• 제43권4호
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• pp.223-232
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• 2008

In order to determine the temporal and spatial variations of nutrient profiles in the shallow pore water columns (upper 30 cm depth) of intertidal sandflats, we measured the salinity and nutrient concentrations in pore water and seawater at various coastal environments along the southern coast of Korea. In the intertidal zone, salinity and nutrient concentrations in pore water showed marked vertical changes with depth, owing to the active exchange between the pore water and overlying seawater, while they are temporally more stable and vertically constant in the sublittoral zone. In some cases, the advective flow of fresh groundwater caused strong vertical gradients of salinity and nutrients in the upper 10 cm depth of surface sediments, indicating the active mixing of the fresher groundwater with overlying seawater. Such upper pore water column profiles clearly signified the temporal fluctuation of lower-salinity and higher-Si seawater intrusion into pore water in an intertidal sandflat near the mouth of an estuary. We also observed a semimonthly fluctuation of pore water nutrients due to spring-neap tide associated recirculation of seawater through the upper sediments. Our study shows that the exchange of water and nutrients between shallow pore water and overlying seawater is most active in the upper 20 cm layer of intertidal sandflats, due to physical forces such as tides, wave set-up, and density-thermal gradient.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.97.1-97.1
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• 2012

Porous ceramics are widely used for applications such as catalysis supports, gas distributors and filters such as DPF. For these purpose, it is important to have proper porosity controlling pore structure while maintaining mechanical and thermal properties. In this work, we have prepared the porous ceramic structures made of reaction bonded silicon nitride with hierarchical pore structures. Uni-directionally aligned pore channels, which are mostly filled with ${\beta}$-Si3N4 whiskers, were achieved by an ice-templating method. The structures of the pore channels and the walls are controllable by the processing conditions, such as solid concentration, freezing rate of the slurry, and additives. We have investigated and characterized the influences of the conditions on the microstructures and the properties, such as porosity, pore size distribution, lamellar thickness, wavelength, and orientations. The compressive strength test and flow test was performed to determine the structural integrity and air permeability.

• 한국지반공학회논문집
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• 제23권6호
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• pp.77-84
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• 2007

유입량과 라이닝에 작용하는 간극수압은 터널 설계시 고려해야 할 중요한 요소 중 하나이다. 간극수압의 발생은 누수를 가속화시키며 라이닝 열화를 초래한다. 본 논문에서는 모형실험을 통하여 배수시스템 기능저하로 인한 간극수압의 발생과 그 영향을 조사하였다. 배수시스템 기능저하거동은 배수재의 투수계수제어법과 유량 조절법으로 모사화 하여 터널 라이닝의 잔류수압발생 메카니즘을 확인하였다. 또한, 유량제어법이 배수시스템 기능저하현상을 모사하기에 보다 더 효과적인 방법임을 알 수 있었다. 모형실험을 수치해석으로 재현한 결과, 배수시스템 기능저하로 인한 영향을 Coupled 수치 모델링을 통해 이론적으로 예측 가능함을 확인할 수 있었다.

• Carbon letters
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• 제11권3호
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• pp.201-205
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• 2010

Activated carbons are well known as adsorbents for gases and vapors. Micro porous carbons are used for the sorption/separation of light gases, whereas, carbon with bigger pore size are applied for removal of large molecules. Therefore, the control of pore size of activated carbon plays a vital role for their use in specific applications. In the present work, steam activation parameters have been varied to control pore size of the resulting activated carbon. It was found that flow rate of steam has profound effect on both surface characteristic and surface morphology. The flow rate of steam was optimized to retain monolith structure as well as higher surface area.

• 약학회지
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• 제35권4호
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• pp.277-282
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• 1991

Rheological, colloidal and micromeritical properties were followed to investigate aging mechanisms of hydrous aluminum oxide suspension using Zeta-meter systems, BET adsorption apparatus, Master sizer and electronmicroscope. The results indicate that hydrous aluminum oxide suspension revealed plastic flow with thixotropy. The viscosity, thixotropy and yield value were increased with increasing concentration. During aging process, the viscosity and thixotropic index were increased by an addition of glycerin, however, sorbitol stabilized aging process of the suspension being accompanied with growth of particle size and reduction in specific surface area, pore area and pore volume, and consistency. Diminution of adsorptive power of the particles was also protected by addition of sorbitol to hydrous aluminum oxide suspension. From these results, one of aging mechanism of hydrous aluminum oxide suspension assumed growth and/or crystallization of colloidal particles in aqueous suspension.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
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• pp.25-28
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• 2004

The capillary number is used to represent the mobilization potential of organic phase trapped within porous media. The capillary number has been defined by three different forms, according to types of flow velocity and viscosity used in the definition of capillary number. This study evaluated the suitability of the capillary number definitions for representing TCE mobilization by constructing capillary number-TCE saturation relationships. The results implied that the capillary number should be correctly employed, according to interest of scale and fluid flow behavior. This study suggests that the pore-scale capillary number may be used only for investigating the organic-phase mobilization at the pore scale because it is defined by the pore-velocity and the dynamic viscosity. The Newtonian-fluid capillary number using Darcy velocity and the dynamic viscosity may be suitable to quantify flood systems representing Newtonian fluid behavior. For viscous-force modified flood systems such as surfactant-foam floods, the apparent capillary number definition employing macroscopic properties (permeability and potential gradient) may be used to appropriately represent the desaturation of organic-phases from porous media.

• 환경위생공학
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• 제13권3호
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• pp.72-78
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• 1998

For investigation into gas permeation characteristics, the porous alumina membrane with asymmetrical structure, having upper layer with 10 nanometer under of pore diameter and lower layer with 36 nanometer of pore diameter, was prepared by anodic oxidation using DC power supply of constant current mode in an aqueous solution of sulfuric acid. The aluminium plate was pre-treated with thermal oxidation, chemical polishing and electrochemical polishing before anodic oxidation. Because the pore size depended upon the electrolyte, electrolyte concentration, temperature, current density, and so on, the the membranes were prepared by controling the current density, as a very low current density for upper layer of membrane and a high current density for lower layer of membrane. By control of current quantity, the thicknesses of upper layer of membranes were about $6{\;}{\mu}m$ and the total thicknesses of membranes were about $80-90{\;}{\mu}m$. We found that the mechanism of gas permeation depended on model of the Knudsen flow for the membrane prepared at each condition.

• 상하수도학회지
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• 제19권2호
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• pp.135-143
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• 2005

It was evaluated that the effect of turbidity removal by Pore Controllable Fiber Filter(PCF) installed in NS(Naksang) small water treatmant plant(system) using under flow water as raw water in the study. The results of the study are as the followings. Firstly, the removal efficiency of turbidity by PCF without coagulation(in operation mode not using coagulants) was mostly below 20 percent. On the other hand, when operation using proper coagulants, that of turbidity was mostly over 80 percent. Secondly, slow sand filtration after PCF, total turbidity removal efficiency of final treated water was 84.3 percent, and the contribution by PCF was 57.1 percent and that of slow sand filtration was 27.7 percent. Therefore the introduction of PCF as pre-treatment process would be helpful to reduce the loading of high turbidity of slow sand filtration. Thirdly, the results of particle counter measurements showed that when operated PCF with coagulants, fine flocs captured or adsorbed at the pore of PCF were flow out into the effluents from 120 minutes after backwashing because of the increase of headloss of PCF. Therefore the decision of backwashing time should made consideration into the outflow of fine flocs from PCF. Fourth, coagulant dosages on PCF at the same turbidity was largely variable because of the effect of the raw water characteristics and the turbidity increase velocity at rainy days, therefore flexible coagulant dosages should be considered rather than fixed coagulant dosage by the influent jar-test result.