• Wind and Structures
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• 제19권1호
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• pp.35-58
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• 2014

A numerical simultaneous solution involving a linear elastic model was applied to study the fluid-structure interaction (FSI) of membrane structures under wind actions, i.e., formulating the fluid-structure system with a single equation system and solving it simultaneously. The linear elastic model was applied to managing the data transfer at the fluid and structure interface. The monolithic equation of the FSI system was formulated by means of variational forms of equations for the fluid, structure and linear elastic model, and was solved by the Newton-Raphson method. Computation procedures of the proposed simultaneous solution are presented. It was applied to computation of flow around an elastic cylinder and a typical FSI problem to verify the validity and accuracy of the method. Then fluid-structure interaction analyses of a saddle membrane structure under wind actions for three typical cases were performed with the method. Wind pressure, wind-induced responses, displacement power spectra, aerodynamic damping and added mass of the membrane structure were computed and analyzed.

• International Journal of Concrete Structures and Materials
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• 제3권1호
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• pp.15-23
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• 2009

Over about 30% of problems in construction is related to water-leaking, and the loss from this problem can incur as much as three times the cost of initial construction. Thus, water vapor pressure is known to be the primary cause of defective waterproofing. Accordingly, the theories on the relationship between water pressure and temperature as well as damp-proofing volume of concrete and the change in vapor pressure volume were reviewed and analyzed in this study by making test samples after spraying a dampness remover and applying waterproofing materials to the prepared test specimens. The result of measuring water vapor pressure with the surface temperature of the waterproofing (fluid-applied membrane) layer at the experimental temperature setting of about $10^{\circ}C$, which is the annual average temperature of Seoul, indicated that (1) the temperature of the fluid-applied membrane elevated to about $40^{\circ}C$, and the water vapor pressure generated from the fluid-applied membrane was about 0.03 N/mm 2 when the surface temperature of the waterproofing layer was raised to about $80^{\circ}C$. (2) when the temperature of the fluid-applied membrane of the waterproofing layer was raised from $30^{\circ}C$ to $35^{\circ}C$, water vapor pressure of about 0.01 N/mm 2 was generated, and (3) when a thermal source was applied to the fluid-applied membrane (waterproofing) layer, the temperature increased from $35^{\circ}C$ to $40^{\circ}C$, and approximately $0.005\;N/mm^2$ of water vapor pressure was generated.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 추계 학술논문 발표대회 논문집
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• pp.147-150
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• 2006

Of the total defects that have occurred recently in the Korean construction market, over 30% are caused by the construction of defective waterproofing, and the phenomenon of air pockets in the waterproofing layer, which is caused by the concrete vapor pressure, is known to be the primary cause of defective waterproofing. Accordingly, in this study the theory about the relationship between water pressure and temperature as well as the damp-proofing volume of concrete and, then, the change of vapor pressure volume was measured and analyzed by making a test sample after spraying a dampness remover and a waterproofing material to a prepared test body. As a result of measuring the water vapor pressure for the surface temperature of the waterproofing layer with the fluid-applied membrane temperature based on about $10^{\circ}C$, which is the average temperature of Seoul, it was found that first, the fluid-applied membrane elevated up to about $40^{\circ}C$, and the water vapor pressure generated from the fluid-applied membrane was about $0.3kgf/cm^2$ when the surface temperature of the waterproofing layer was raised up to about $80^{\circ}C$. Second, when the fluid-applied membrane temperature of the waterproofing layer was raised from $30^{\circ}C\;to\;35^{\circ}C,\;about\;0.1kgf/cm^2$ of water vapor pressure was generated, and when supplying a thermal source to raise the fluid-applied membrane temperature of the waterproofing layer from $35^{\circ}C\;to\;40^{\circ}C$, approximately $0.05kgf/cm^2$ of water vapor pressure was generated.

• 한국건축시공학회지
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• 제9권6호
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• pp.91-98
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• 2009

건축공사 중 인간에게 많은 영향을 미치는 습기와 물에 대한 피해로부터 주거 생활을 보호하는 성능을 가진 것이 방수공사이다. 건축 방수공사의 하자로 인한 보수비는 방수층 자체의 보수비용뿐만 아니라 연계공종의 피해로 인한 연계공종의 보수비용 또한 추가되어, 방수공사의 전체적인 보수비용은 더욱 높아진다. 하지만, 방수공사의 하자를 미연에 방지할 수 있는 정량적이고 효율적인 관리방안이 부족한 실정이다. 기존 문헌 고찰과 사례 분석 결과, 지하층 방수공사 하자가 빈번하게 나타났으며, 여러 공법 중 도막방수가 가장 많이 사용되고 있었다. 이에 본 연구에서는 지하층 도막방수공사에 대한 하자 사례분석을 하였으며, 이를 미연에 방지하기 위한 방안으로 FMEA(Failure Mode and Effect Analysis) 기법을 변형한 R-FMEA 방법을 고안하였다. R-FMEA 쉬트에 대한 전문가 설문을 통하여 지하층 도막방수공사 하자 유형 중 가장 위험성이 큰 방수공사 하자 유형을 도출하여, 중요하게 관리되어야 하는 요인들을 도출하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제13권2호
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• pp.123-140
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• 2009

The effect of a solute concentration difference on the osmotic transport of water through the semi-permeable membrane of a simple cell model is investigated. So far, most studies on osmotic phenomena are described by simple diffusion-type equations ignoring all fluid motion or described by Stokes flow. In our work, as the governing equations, we consider the coupled full Navier-Stokes equations which describe the fluid motion and the full transport equation that takes into account of convection and diffusion effects. A two dimensional finite difference model has been developed to simulate the velocity field, concentration field, and semi-permeable membrane movement. It is shown that the cell swells to regions of lower solute concentration due to the uneven water flux through the semi-permeable membrane. The simulation is applied on a red blood cell geometry and the relevant results are presented.

• 한국유체기계학회 논문집
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• 제17권2호
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• pp.30-34
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• 2014

Membrane distillation (MD) is a thermal driven separation process in which separation a hydrophobic membrane is a barrier for the liquid phase, letting the vapor phase pass through the membrane pores. Therefore, a porous and hydrophobic membrane should be used in membrane distillation. MD cannot work if water penetrates into the pores of the membrane (membrane wetting). Accordingly, it is necessary to prevent wetting of MD membranes and to remove water inside the pores of the wetted membranes if possible. In this context, our study aimed to develop methods to recover wetted membranes in MD processes. Poly-vinylidene fluoride (PVDF) membranes were used in this study. A laboratory-scale direct contact MD (DCMD) system was used to examine the effect of operating parameters on wetting. For dewetting the wetted membranes, specific techniques including the use of high temperature air were applied. The performances of the membranes before and after dewetting were compared in terms of flux, salt rejection and liquid entry pressure(LEP). The surface morphology of dewetted membrane was confirmed by scanning electron microscope (SEM).

• Biomolecules & Therapeutics
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• 제14권1호
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• pp.19-24
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• 2006

Atrial chambers serve as mechanosensory systems during the haemodynamic or mechanical disturbances, which initiates arrhythmia. Atrial myocytes, lacking t-tubules, have two functionally separate sarcoplasmic reticulums (SRs): those at the periphery close to the surface membrane, and those at the cell interior (center) not associated with the membrane. To explore possible role of fluid pressure (FP) in the regulation of atrial local $Ca^{2+}$ signaling we investigated the effect of FP on subcellular $Ca^{2+}$ signals in isolated rat atrial myocytes using confocal microscopy. FP was applied to whole area of single myocyte with pressurized automatic micro-jet (200-400 $mmH_2O$) positioned close to the cell. Application of FP enhanced spontaneous occurrences of peripheral and central $Ca^{2+}$ sparks with larger effects on the peripheral release sites. Unitary properties of single sparks were not altered by FP. Exposure to higher FP often triggered longitudinal $Ca^{2+}$ wave. These results suggest that fluid pressure may directly alter excitability of atrial myocytes by activating $Ca^{2+}$-dependent ionic conductance in the peripheral membrane and by enhancing spontaneous activation of central myofilaments.

• 한국응용과학기술학회지
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• 제24권3호
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• pp.233-237
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• 2007

This study is focused on the possibility of copper alloy metal fiber for an antimicrobial activity in the water soluble metal working fluids. Electrochemical potential of Cu/Zn ion is -268mV, and easily makes radicals with molecular oxygen. Especially, hydroperoxide radical shows strong toxicity to the strains. Plasma membrane causes conformational change when hydroperoxide radical binds to plasma membrane. Elution of copper ion from copper alloy metal fiber is detected in metal working fluid. As a result antimicrobial activity of copper alloy metal fiber in metal working fluid is superior to that of copper fiber.

• 한국유체기계학회 논문집
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• 제9권2호
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• pp.19-24
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• 2006

Nano fountain-pen is a novel device to make the constant patterning in micro process using new designed probe. Fountain-pen nanolithography (FPN) is applied for constant supply of liquid in conjunction of patterns and surface variation in the micro process. In this study, nuo fountain-pen is composed with reservoir, micro channels, tip and scondary chamber. Instead of traditional method only using capillary force, liquid can be definitely and exactly injected with membrane pumping by the repulse force of tip. It is dfficult to perform experiments in the micro range so that we carried out a numerical analysis for internal flow, using a commercial code, FlUENT, The velocity, pressure and flow rate are obtained under laminar, unsteady, three-dimensional incompressible flow with no-slip condition, and results are graphically described.

• 한국막학회:학술대회논문집
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• 한국막학회 2004년도 Proceedings of the second conference of aseanian membrane society
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• pp.15-18
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• 2004

Computational fluid dynamics (CFD) was applied to modeling particle dynamics in microfiltration (MF). The rejection properties of poly methylmethacrylate (PMMA) and polystyrene (PS) were calculated. Calculated rejection (R) of PMMA was independent with the porosity of the membrane, and the R was constant in the range of volume flux between $1\times 1-^{-4}-1\times 10^{-2}$ m/s. These observations were in quantity agreement with our experimental observations. The dependence of PMMA and PS rejection on the ratio of particle diameter and pore diameter were good agreement with the experimental values, which suggesting that the validity of CFD simulation to evaluate rejection of particle in MF membranes. Change of rejection of PMMA as a function of time was molded based on the CFD result which explained well the experimental observation.