• 청정기술
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• 제23권2호
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• pp.140-147
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• 2017

본 연구에서는 연료전지용 디젤 흡착 탈황 반응기에 사용된 촉매를 재생하는 공정을 수치해석을 통해 모사하고 분석하여 관련된 기초 공정 정보를 도출하였다. 촉매 재생에 사용되는 질소 퍼지가스의 유량, 충전된 탈황촉매의 투과율, 반응기의 크기, 반응기의 단열 성능에 따른 정상상태 해석을 통해 각각의 요소가 촉매 재생에 미치는 영향들을 살펴보았다. 온도의 영향을 거의 받지 않았던 탈황공정과 달리 촉매의 재생 공정에서는 온도 변화에 따라 영향을 크게 받았으며 이전 탈황 연구에서 중요한 공정 변수였던 충전된 촉매의 투과도, 충전층의 공극률 등은 큰 영향을 미치지 못했다. 비정상상태 해석을 수행하여 재생에 소요되는 시간을 예측하였으며 퍼지가스의 유량과 온도를 변화시키며 재생에 소요되는 시간을 분석한 결과, 퍼지가스의 유량을 높이는 것 보다 온도를 높이는 것이 재생에 더 효율적임을 확인하였다. 본 연구 결과는 선박 연료전지용 디젤의 흡착 탈황 반응기의 재생 공정 개발에 활용될 것으로 기대된다. 또한 본 결과는 연료전지뿐 아니라 일반적으로 정유사에서 생산되는 디젤유의 황 함유량을 감소시키는 저황 시스템 디자인에 활용될 수 있으며 이러한 의미에서 석유화학 산업의 청정화 기술 확보에 이바지할 것으로 기대된다.

• The Korean Journal of Physiology and Pharmacology
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• 제19권1호
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• pp.1-7
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• 2015

Our previous study has shown berberine prevents damage to the intestinal mucosal barrier during early phase of sepsis in rat through mechanisms independent of the NOD-like receptors signaling pathway. In this study, we explored the regulatory effects of berberine on Toll-like receptors during the intestinal mucosal damaging process in rats. Male Sprague-Dawlay (SD) rats were treated with berberine for 5 d before undergoing cecal ligation and puncture (CLP) to induce polymicrobial sepsis. The expression of Toll-like receptor 2 (TLR 2), TLR 4, TLR 9, the activity of nuclear factor-kappa B ($NF-{\kappa}B$), the levels of selected cytokines and chemokines, percentage of cell death in intestinal epithelial cells, and mucosal permeability were investigated at 0, 2, 6, 12 and 24 h after CLP. Results showed that the tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) and interleukin-6 (IL-6) level were significantly lower in berberine-treated rats compared to the control animals. Conversely, the expression level of tight junction proteins, percentage of cell death in intestinal epithelial cells and the mucosal permeability were significantly higher in berberine-treated rats. The mRNA expression of TLR 2, TLR 4, and TLR 9 were significantly affected by berberine treatment. Our results indicate that pretreatment with berberine attenuates tissue injury and protects the intestinal mucosal barrier in early phase of sepsis and this may possibly have been mediated through the TLRs pathway.

• Macromolecular Research
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• 제15권5호
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• pp.412-417
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• 2007

In the present study, crosslinked poly(vinyl alcohol) (PVA) membranes were prepared at different temperatures using poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA) (PVA:PSSA_MA = 1:9). The hybrid mem-branes were prepared by varying the TEOS content between 5 and 30 wt%. The PSSA_MA was used both as a crosslinking agent and the hydrophilic group donor ($-SO_3H$ and/or-COOH). The proton conductivity increased with up to 20 wt% TEOS, but decreased above this level, although the water content decreased with increasing TEOS content. This result suggests that the silica doped into the membrane improved the formation of proton-conduction pathways due to the absorption of molecular water. The PVA/PSSA_MA/Silica containing TEOS 20% showed both high proton conductivity (0.026 S/cm at $90^{\circ}C$) and low methanol permeability ($5.55{\times}10^{-7}cm^2/s$).

• Korean Chemical Engineering Research
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• 제61권2호
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• pp.202-207
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• 2023

태양광과 풍력발전의 잉여전기를 공급받아 수전해를 구동하는 경우 날씨 변동에 따라 구동과 정지를 반복해야한다. 수전해를 구동하다 정지하면 잔류 수소와 산소에 의해 PEM 연료전지와 같은 상태가 되고, 구동 중 형성된 수전해의 높은 전위 때문에 전극과 고분자막이 정지 중에도 열화될 가능성이 높다. 본 연구에서는 PEM 수전해가 구동/정지 반복과정에서 전극과 고분자막의 열화가 얼마나 진행되는지 확인하고자, 144시간 동안에 구동/정지 횟수를 변화시키며 성능 감소를 측정하였다. 전극 촉매 활성면적 변화와 고분자막의 수소투과도와 불소유출속도 등을 분석해 전극과 고분자막의 특성 변화를 측정했다. 전체적으로 정지 횟수가 증가할수록 PEM 수전해 성능이 감소했다. 144시간동안에 5회 정지했을 때 IrO_x 촉매 활성이 30% 이상 감소하였고, 수소투과도는 80% 증가해서 전극과 고분자막이 모두 열화됨을 확인했다.

• Composites Research
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• 제21권1호
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• pp.1-7
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• 2008

복합재 고압 용기는 우수한 기계적 강도를 유지하면서 경쟁적인 무게절감을 얻을 수 있는 복합재의 장점으로 인해 최근에 많이 사용되고 있다. 하지만 고압에서 발생하는 복합재의 기밀 문제(permeability)를 보완하기 위해 금속으로 덧대는 Type 3 형태의 구조로 많이 사용된다. 그러나 복잡한 기하학적 형상, 제조공정 변수 등으로 인해 차입 3 형태의 압력용기를 설계하는 데에는 많은 어려움이 뒤따른다. 따라서 본 연구에서는 이러한 변수들을 고려하는 준측지궤적 알고리즘(semi-geodesic algorithm)과 최적화를 위한 유전자 알고리즘을 적용하여 차입 3 복합재 압력용기의 GUI(graphic user interface) 최적설계 프로그램을 개발하였다. 또한 개발된 프로그램을 이용하여 연료 전지 자동차에 적용되는 350/700 바 수소저장용기에 대해 최적 설계를 수행하였다.

• Bulletin of the Korean Chemical Society
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• 제34권6호
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• pp.1651-1655
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• 2013

Anion exchange membranes for a vanadium redox flow battery (VRB) were prepared by pore-filling on a PE substrate with the copolymerization of vinylbenzyl chloride (VBC) and glycidyl methacrylate (GMA). The ion exchange capacity, water uptake and weight gain ratio were increased with a similar tendency up to 65% of GMA content, indicating that the monomer improved the pore-filling degree and membrane properties. The vanadium ion permeability and open-circuit voltage were also investigated. The permeability of the VG65 membrane was only $1.23{\times}10^{-7}\;cm^2\;min^{-1}$ compared to $17.9{\times}10^{-7}\;cm^2\;min^{-1}$ for Nafion 117 and $1.8{\times}10^{-7}\;cm^2\;min^{-1}$ for AMV. Consequently, a VRB single cell using the prepared membrane showed higher energy efficiency (over 80%) of up to 100 cycles compared to the commercial membranes, Nafion 117 (ca. 58%) and AMV (ca. 70%).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.359.1-359.1
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• 2016

The electromagnetic (EM) properties of media, such as propagation, focusing and scattering, strongly rely on the electric permittivity and the magnetic permeability of media. Recently, artificially-created metamaterials (MMs) composed of periodically-arranged unit cells with tailored electric permittivity and magnetic permeability have drawn wide interest due to their capability of adjusting the EM response. MM absorbers using the conventional sandwich structures usually have very high absorption at a certain frequency, and the absorption properties of MMs can be adjusted simply by changing the geometrical parameters of unit cell. In this work, we suggested an incident-angle-independent broadband perfect absorber based on resistive layers. We analyze the absorption mechanism based on the impedance matching with the free space and the distribution of surface currents at specific frequencies. From the simulation, the absorption was expected to be higher than 96% in 1.4-6.0 GHz. The corresponding experimental absorption was found to be higher than 96% in 1.4-4.0 GHz, and the absorption turned out to be slightly lower than 96% in 4.0-6.0 GHz owing to the irregularity in the thickness of resistive layers.

• Journal of electromagnetic engineering and science
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• 제12권1호
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• pp.26-31
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• 2012

We have proposed a metamaterial lens that enables sub-wavelength focusing, which is shorter than an operating wavelength. Our lens is a two dimensional array of a unit cell consisting of a metallic dual-plate printed on a dielectric substrate. The unique dual-plate structure provides negativeness both in permittivity and permeability, with no help from conventional additional structures, which are normally printed on the opposite of metallic patterns. Therefore, we can focus a source (or an image) in a tiny distance shorter than the free space wavelength (${\lambda}$) at the frequencies of interest. Furthermore, since the proposed geometry does not need separate supplementary structures to acquire negative permittivity or permeability, our lens is much simpler than conventional metamaterial lenses, which is a strong point in practical applications. We have validated sub-wavelength focusing ability in a 6 GHz frequency band through an experiment of near field scanning, which provided the width of about 0.19 ${\lambda}$ at a half maximum of a peak value of an measured image. The width of the focused image through the lens is more than 4 times shorter than that without the lens, which confirms the validity of our design approach.

• 대한한방소아과학회지
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• 제7권1호
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• pp.1-16
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• 1993

Experimental studies were done to research the clinical effect of Woohwangporhyonghwan(minus REALGAR and CINNABARIS) and Saengnyosamultang on the Anti-allergie effect in rats and mice. The results obtained as follows: 1. (1) In the effects of Woohwangporhyonghwan(minus REALGAR and CINNABARIS) and Saengnyosamultang on vascular permeability responses to intradermal histamin in rats, Woohwangporhyonghwan(minus REALGAR and CINNABARIS) and Saengnyosamultang revealed significant effect. (2) In the effects of Woohwangporhyonghwan(minus REALGAR and CINNABARIS) and Saengnyosamultang on vascular permeability responses to intradermal serotonin in rats, Woohwangporhyonghwan(minus REALGAR and CINNABARIS) revealed significant effect. 2. In the 48 hour homologous passive cutaneous anaphylaxis in rats provoked by the Ig E-like antibody against egg albumin, Woohwangporhyonghwan(minus REALGAR and CINNABARIS) and Saengnyosamultang revealed significant effect. 3. In the delayed type hypersensitivity responses to picryl chloride in mice, Woohwangporhyonghwan(minus REALGAR and CINNABARIS) revealed significant effect. 4. In the delayed type hypersensitivity responses to SRBC(Sheep Red Blood cell) in mice, Woohwangporhyonghwan(minus REALGAR and CINNABARIS) and Saengnyosamultang revealed significant effect. According to above-stated results, Woohwangporhyonghwan(minus REALGAR and CINNABARIS) and Saengnyosamultang were concluded to be effective as anti-allergic regimen and recommended to be used for treatment of allergic diseases.

• Journal of Microbiology and Biotechnology
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• 제19권10호
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• pp.1230-1237
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• 2009

The selective plugging strategy of Microbial Enhanced Oil Recovery (MEOR) involves the use of microbes that grow and produce exopolymeric substances, which block the high permeability zones of an oil reservoir, thus allowing the water to flow through the low permeability zones leading to increase in oil recovery. Bacillus licheniformis TT33, a hot water spring isolate, is facultatively anaerobic, halotolerant, and thermotolerant. It produces EPS as well as biosurfactant and has a biofilm-forming ability. The viscosity of its cell-free supernatant is $120\;mPa{\cdot}s$ at $28^{\circ}C$. Its purified EPS contained 26% carbohydrate and 3% protein. Its biosurfactant reduced the surface tension of water from 72 to 34 mN/m. This strain gave $27.7{\pm}3.5%$ oil recovery in a sand pack column. Environmental scanning electron microscopy analysis showed bacterial growth and biofilm formation in the sand pack. Biochemical tests and Amplified Ribosomal DNA Restriction Analysis confirmed that the oil recovery obtained in the sand pack column was due to Bacillus licheniformis TT33.