• 멤브레인
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• 제29권1호
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• pp.37-43
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• 2019

본 연구에서는 분자동역학에서 원자의 움직임을 정의하는 가장 중요한 요소인 force-field가 실제 고분자 및 기체 분자의 움직임에 어떠한 영향을 주는지 알아보고자 하였다. Repeat unit과 고분자 구조는 본 연구에서 사용된 5종의 force-field 에서 모두 정상적으로 작용을 하였고, 최종 고분자 3D 모델에서 고분자 linear chain의 분포에서도 큰 차이를 보이지 않았다. 그러나 실제 기체 분자의 움직임은 매우 다른 경향을 나타내었으며, 이는 같은 functional form을 사용하는 COMPASS와 pcff 에서도 관찰되었다. 따라서 동일한 구조라고 하더라도 기체 분자의 운동은 시간에 따라 지속적으로 force-field의 영향 하에서 움직이기 때문에, 고분자 linear chain과 같은 거대 분자에 비하여 그 영향을 훨씬 크게 받는다는 것을 알 수 있으며, 결론적으로 서로 다른 force-field의 사용 시에는 결과 비교에 있어서도 매우 신중을 기해야 할 것이다.

• 멤브레인
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• 제23권6호
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• pp.393-408
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• 2013

고분자 분리막을 이용한 기체 분리막은 높은 에너지 효율, 경제적인 장점으로 최근 수년간 지속적으로 개발되어 왔다. 최적화된 경제적 성능을 얻기 위하여 기체 분리막은 높은 투과도와 선택도를 가져야 한다. 따라서 기체분리 분리막용으로 다양한 고분자를 시험한 연구 결과들이 보고되어 왔다. 다양한 소재 중, 폴리이미드는 다양한 기체인자에 대하여 높은 투과 선택도와 높은 화학적 열적 안정성, 그리고 물리적 안정성으로 많은 주목을 받아왔다. 따라서 본고에서는 기체분리용 폴리이미드 소재의 개발동향과 분리막의 제조방법, 기체 분리의 원리에 대하여 다루었다.

• Membrane and Water Treatment
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• 제9권1호
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• pp.63-68
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• 2018

Molecular dynamics simulations were used to study the removal of Cd(II) as a heavy metal from wastewater using armchair carbon nanotube, boron nitride nanotube and silicon carbide nanotubes under applied electric field. The system contains an aqueous solution of $CdCl_2$ as a heavy metal and a (7,7) nanotube as a nanostructured membrane, embedded in a silicon nitride membrane. An external electric field was applied to the considered system for the removal of $Cd^{2+}$ through nanotubes. The simulation results show that in the same conditions, considered armchair nanotubes were capable to remove $Cd^{2+}$ from wastewater with different ratios. Our results reveal that the removal of heavy metals ions through armchair carbon, boron nitride and silicon carbide nanotubes was attributed to the applied electric field. The selective removal phenomenon is explained with the calculation of potential of mean force. Therefore, the investigated systems can be recommended as a model for the water treatment.

• Coupled systems mechanics
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• 제6권4호
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• pp.501-522
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• 2017

This paper introduces a numerical procedure to incorporate elasto-plastic local deformation effects in the dynamic analysis of beams. The appealing feature is that simple beam type finite elements can be used for the global model which needs not to be altered by the localized elasto-plastic deformations. An overlapping local sophisticated 2D membrane model replaces the internal forces of the beam elements in the predefined region where the localized deformations take place. An iterative coupling technique is used to perform this replacement. Comparisons with full membrane analysis are provided in order to illustrate the accuracy and efficiency of the method developed herein. In this study, the membrane formulation is able to capture the elasto-plastic material behaviour based on the von Misses yield criterion and the associated flow rule for plane stress. The Newmark time integration method is adopted for the step-by-step dynamic analysis.

• 한국막학회:학술대회논문집
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• 한국막학회 2004년도 Proceedings of the second conference of aseanian membrane society
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• pp.33-38
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• 2004

Molecular modeling of gas permeation through zeolite membranes with/without intercrystalline region was carried out. Molecular dynamics (MD) and Monte Carlo (MC) simulations were performed to estimate the diffusion coefficient and adsorption parameters respectively, and our proposed combined method of molecular simulation techniques with a permeation theory (CMP) was used to estimate gas permeability. The calculated permeability of gases (Ar, He, Ne, $N_2$, $0_2$, $CH_4$) at 301 K for the single crystal membrane model was about one order of magnitude larger than the experiential values, although the dependence on the molecular weight of the permeating species agreed with experiments. On the other hand, the estimated permeability using the diffusivity and adsorption parameters of the intercrystalline region model was in good agreement with the experiments. The consistency between experiments and the estimated values means the importance of considering the intercrystalline region and the validity of CMP method to predict the performance of zeolite membranes.

• 드라이브 ㆍ 컨트롤
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• 제16권2호
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• pp.66-71
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• 2019

In this study, flow analysis and dehumidification experiments were performed on hollow fiber membrane module to confirm the dehumidification characteristics for its different configurations. The CFD for the three different models was conducted using $30^{\circ}C$ temperature and 30%RH inlet humidity for quantitative analysis. Each model has different shape parameters i.e. the number of baffles. Comparison between flow analysis results and dehumidification experiment results revealed a percentage error of about 5%. The difference in relative humidity between the inlet and outlet for each model was calculated using flow analysis data. It was established that the difference in relative humidity of the inlet and outlet for the refined model with three baffles was highest among the three modeled modules of hollow fiber membrane module, i.e. around 9%.

• Journal of Electrochemical Science and Technology
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• 제14권1호
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• pp.38-50
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• 2023

Proton exchange membrane fuel cell (PEMFC) is a portable and clean power generation device. The structural arrangement of the flow field has a significant influence on the delivery efficiency of PEMFC. In this article, a new bionic flow channel is designed based on the inspiration of a spider shape. The branch channel width and branch corner are studied as the focus, and its simulation is carried out by the method of computational fluid dynamics (CFD). The results show that when channel width/rib width and corner of the branch are 1.5 and 130° , respectively, it is the best numerical combination and the cell comprehensive performance is excellent. The final model using this numerical combination is compared with the traditional flow channel model to verify the advancement of this scheme.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.403.2-403.2
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• 2016

Porous materials play a significant role in energy storage and conversion applications such as catalyst support for polymer electrolyte membrane fuel cell. In particular, hierarchical porous materials with both micropores (poresize, ${\delta}$ < 2 nm) and regularly arranged mesopores (2 nm < ${\delta}$ < 50 nm) are known to greatly enhance the efficiency of catalytic reactions by providing enormous surface area as well as fast mass transport channels for both reactants and products from/to active sites. Although it is generally agreed that the microscopic structure of the porous materials directly affects the performance of these catalytic reactions, neither detailed mechanisms nor fundamental understanding are available at hand. In this study, we propose an atomistic model of hierarchical nanostructured porous carbons (HNPCs) in molecular dynamics simulations. By performing a systematic study, we found that structural features of the HNPC can be independently altered by tuning specific synthesis parameters, while remaining other structures unchanged. In addition, we show some structure-property relations including mechanical and gas transport properties.

• BMB Reports
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• 제44권8호
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• pp.517-522
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• 2011

Mitochondrial dynamics not only involves mitochondrial morphology but also mitochondrial biogenesis, mitochondrial distribution, and cell death. To identify specific regulators to mitochondria dynamics, we screened a chemical library and identified niclosamide as a potent inducer of mitochondria fission. Niclosamide promoted mitochondrial fragmentation but this was blocked by down-regulation of Drp1. Niclosamide treatment resulted in the disruption of mitochondria membrane potential and reduction of ATP levels. Moreover, niclosamide led to apoptotic cell death by caspase-3 activation. Interestingly, niclosamide also increased autophagic activity. Inhibition of autophagy suppressed niclosamide-induced cell death. Therefore, our findings suggest that niclosamide induces mitochondria fragmentation and may contribute to apoptotic and autophagic cell death.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1176-1179
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• 2004

A new cell-cross bridge mechanics model is proposed to analyze the mechanics of heart muscle. Electrophysiology of a cardiac cell is numerically approximated using the previous model of human ventricular myocyte. Ion transports across cell membrane initiated by action potential induce excitation-contraction mechanism in the cell via cross bridge dynamics. Negroni and Lascano model (NL model) is employed to compute the tension of cross bridge closely related to ion dynamics in cytoplasm.