• 한국항공우주학회지
• /
• 제38권5호
• /
• pp.421-426
• /
• 2010

본 논문에서는 코너에서 대각선방향으로 인장하중을 받고 있는 접힌자국이 있는 사각형 멤브레인에서 두께가 주름 거동에 미치는 영향을 기하학적 비선형 후좌굴 유한요소해석을 통하여 연구하였다. 멤브레인은 쉘 요소로 모델링 하였고 좌굴을 발생시키기 위하여 면외방향으로 미소의 무작위성 기하학적 결함을 메쉬에 가하였다. 해석은 접히지 않은 원멤브레인과 수직방향으로 접힌 멤브레인에 대해 수행하였고 그 결과를 비교하였다. 해석결과 멤브레인의 두께가 감소함에 따라 주름의 발생과 성장을 크게 촉진함을 알 수 있었다. 또한 접힌 자국의 초기 전개각이 증가할수록 국부주름의 낮은 하중에서 발생하였으나 전역주름으로의 성장은 지연되는 경향을 보였다.

• 한국항공우주학회지
• /
• 제36권5호
• /
• pp.483-490
• /
• 2008

마이크로 추진장치에서 노즐의 소형화는 많은 유동손실을 유발한다. 이러한 유동손실을 극복하기 위해 본 연구에서는 열적발산원리를 이용한 마이크로 추진장치에 대한 기초연구를 진행하였다. 움직이는 부품 없이 오직 온도구배만으로 추진제를 낮은 온도에서 높은 온도로 자체 펌핑이 가능한 열적발산장치를 설계, 제작 하였으며, 진공환경에서 누센수에 따른 맴브레인 압력구배효율을 분석하였다. 실험결과 천이영역에서는 두꺼운 맴브레인의 효율이 다소 높았으며, 자유분자영역에서는 두께에 관계없이 최대 압력구배 효율이 82%까지 증가하는 것을 확인할 수 있었다.

• 상하수도학회지
• /
• 제30권3호
• /
• pp.327-334
• /
• 2016

The effects of dissolved inorganic and organic matter in seawater and the characteristics of fouling on the membrane surface were investigated within membrane distillation (MD) process. The changes of the membrane flux of PE and PVDF hollow fiber membranes under natural and synthetic seawater were compared with given variances of temperature. The flux of both membranes under the synthetic seawater, without any organic matter, were higher than that of the natural seawater, indicating the organic fouling on the membrane surface. The surface of the membrane was analyzed using scanning electron microscope (SEM) to examine the fouling. The experiment with organics has shown the formation of thin film over the membrane surface, while the experiment with inorganics has shown only the formation of inorganic crystals. The results indicated the organic matter as the major foulants and that the organics affected the formation of the crystals. Permeate water conductivity of all conditions verified the quality of the water to be better if not similar to that of RO.

• 한국재료학회지
• /
• 제12권3호
• /
• pp.205-210
• /
• 2002

The HPS(High Porosity Support, 39.3%) and the LPS( Low Porosity Support, 18.7%) were fabricated to investigate the phase transformation and the chance of microstructure with porosity of alumina support. Alumina sol was made using aluminum tri-sec $butoxide(ATSB,\; Al(O-Bu)_3)$, the membrane on porous support with different porosity and the membrane without support were fabricated. The $\theta$-to ${\alpha}-A1_2O_3$ phase transformation in the membranes was investigated using thin film X-ray diffraction (XRD), and the change of microstructure was observed using scanning electron microscopy(SEM). XRD patterns showed that the membrane on LPS and HPS had 10$0^{\circ}C$, 5$0^{\circ}C$ higher $\theta$-to ${\alpha}-A1_2O_3$ transformation temperature compared to the unsupported membrane. A similar effect was also observed in microstructure of the membranes, theoritical temperature difference were 97$^{\circ}C$ and 44$^{\circ}C$ by Crapeyron equation.

• 한국산학기술학회논문지
• /
• 제7권6호
• /
• pp.1292-1295
• /
• 2006

세 종류의 전해질 수용액(염화암모늄형, 염화아연형, 알칼리형)과 조해성재료($CaBr_2$ 또는 $CaCl_2$)를 filter paper 내부에 함침시켜 망간 일차전지용 전해질막을 제조하였다. 전해질막의 두께는 $250{\sim}300{\mu}m$ 이며 유연성 또한 매우 좋았다. 전해질막의 전기화학적 특성은 수분공급을 위해 첨가된 조해성 재료의 종류 및 함량에 크게 의존하였고, $CaCl_2$가 첨가된 계에서 상대적으로 높은 이온전도도 및 방전용량이 얻어졌다.

• 멤브레인
• /
• 제30권2호
• /
• pp.111-123
• /
• 2020

산업화와 기후 변화는 깨끗한 식수에 대한 수요 증가를 초래하였다. 막분리공정을 이용한 해수담수화는 물의 수요에 대한 요구를 채울 수 있는 경제적으로 실현 가능한 대안 중 하나이다. 막분리공정에서 2차원 재료들은 기존 역삼투분리막(reverse osmosis membrane) 기반의 폴리아마이드 박막복합막(TFC-PA)과 비교하였을 때 막의 강도를 높여주고 투수성을 용이하게 하며 높은 염제거율 및 높은 선속률과 선택성을 보여준다. 이 리뷰 논문에서는 재료, 합성, 특징, 해수담수화 과정을 기반으로 다양한 2차원 재료로 구성된 복합막들을 소개하고 있다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2008년 영문 학술대회
• /
• pp.866-870
• /
• 2008

In this study, we designed cold gas propulsion system with minimum 0.25 mm nozzle and micro-thrust measurement system to analyze flow characteristic of micro propulsion system in ambient and vacuum condition. Argon and Nitrogen are used for propellant and the result of experiments is compared with CFD analysis and theory. But there is a point where reduced scale versions of conventional propulsion systems will no longer be practical. Therefore, a fundamentally different approach to propulsion systems was taken. That is thermal transpiration based micro propulsion system. It has no moving parts such as lubricants, pressurizing system and can pump the gaseous propellant by temperature gradient only(cold to hot). We are advancing basic research of propulsion system based on thermal transpiration in vacuum conditions and had tried experiment process and theoretical access in advance. To characterize membrane of Knudsen pump, we select Polyimide material that has low thermal conductivity(0.29 W/mK) and can stand high temperature($300^{\circ}C$) for long time. And we fabricated hole diameter 1, 0.5, 0.2, 0.1 mm using precision manufacturing. Experimental results show that pressure gradient efficiency of Knudsen pump is increased to maximum 82% according to Knudsen number and thick membranes are more effective than thin membranes in transition flow regime.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.794-797
• /
• 2004

In this study, tensile adhesive strength(TAS) test was carreid out for evaluated the effects of temperature conditions (-20, -10, 0, 5, 10, 20, 30, $40^{\circ}C$) on the tensile adhesive characteristics about 4 type waterproofing membranes which were commercially used in bridge decks. And, failure appeariences of waterproofing systems in each temperature after TAS test were observed the sawing surfaces of waterproofing systems for whether or not damaged of waterproofing membranes. Also, correction coefficient of TAS with temperature were calculated using 4 type waterproofing membrane. It could be shown that the higher TAS and shear adhesive strength, the lower temperature, regardless of the type of waterproofing membrane. Temperature sensibility of TAS was especially remarkable in epoxy membrane. Failure type was occurred the ductile failure in $30^{\circ}C\;and\;40^{\circ}C$. From these results, it was shown that if ambient temperature above $30^{\circ}C$ maintains for a long time, waterproofing membrane will be deformed by softening. Otherwise, waterproofing membrane in temperature below $20^{\circ}C$ shown that occurred the brittle failure. From the results of visual observation of cutting surface for specimen, the thin waterproofing membranes shown indented by hot aggregate of the asphalt mixtures. Therefore, it could be known that the specification of waterproofing membrane thickness is necessary by waterproofing membrane type. As temperature change varied with pavement depth, the interface temperature was more important than ambient temperature in TAS test. Now, TAS test results were limited only in $-10^{\circ}C\;and\;20^{\circ}C$ temperature, but correction coefficient of TAS by ambient temperature could be used as a solution to deal with this problem.

• Applied Microscopy
• /
• 제22권1호
• /
• pp.33-41
• /
• 1992

To clarify the exocytotic features in adrenal medullary aminergic cells, the authors observed rat adrenal medulla prepared by the TAGO method with transmission electron microscope. Rat adrenal medulla contains two types of aminergic cells, adrenergic and noradrenergic, as described. They were present as a group. In a single group both adrenergic and noradrenergic cells were present, but the same kind of cells showed the tendency forming small groups. Adrenergic cells were characterized with the granules having relatively electroluscent cores. These granules were relatively uniform in size, and the cores filled the granules with only thin halos. Noradrenergic cells were characterized with the granules of various size and forms. Most of the cores of these granules were generally more electron-dense than those of the adrenergic cells and only partly filled the granules without forming the halos. But, some granules were very similar in the shape and electron density as those of the adrenergic cells. Even empty-looking granules were present. Exocytotic figures with the classical omega figures were observed in both types of aminergic cells, but they were more frequent in adrenergic cells. These figures were mainly present along the plasma membranes toward the capillary. The excreted materials could be identified in the cleft of the omega figures. Apocrine-like secretory patterns but without cytoplasmic rims were identified in noradrenergic cells. Some vesicles, possibly formed from the cytoplsmic tubular systems were released. Some irregular lamellar structures of varying sizes were also observed. They looked like membranous structures sneaking through the plasma membranes. We could not, however, found any evidences of their involvement in exocytotic processes. These were present toward the capillaries and found only in the adrenergic cells. The authors conclude that the secretory processes in adrenal chromaffin cells may include not only the classical exocytotic processes but also the unusual direct secretions of granules or parts of cellular organelles. The membranous lamellar structures may indicate the remnants of excreted granules or functionally inactive excess membranes of the organelles removed from the cytoplasm.

• Korean Chemical Engineering Research
• /
• 제55권1호
• /
• pp.68-73
• /
• 2017

공기 중 분포하는 직경 $0.01{\mu}m{\sim}10{\mu}m$ 이하의 공기 중 미세입자는 섬유 층으로 구성된 멤브레인을 이용하여 제거될 수 있다. 전기 방사 기술, 용융방사, 용액방사, 겔 상태방사와 같은 필터 섬유 제조 기술 중 전기 방사 기술이 최근 가장 주목 받고 있으며, 다른 기술들에 비하여 수백 나노~수십 마이크로미터 정도의 균일한 직경의 섬유를 제조할 수 있다. 전기 방사 기술로 개방된 내부 구조, 넓은 다공성, 내부 표면적을 가지는 멤브레인을 제조할 수 있으므로, 전기 방사 멤브레인의 여과 성능이 눈에 띄는 향상을 보일 것으로 예상된다. 본 연구에서는 멤브레인 필터 섬유 두께, 밀도, 탄소나노튜브 첨가 등에 따른 분리 효율을 비교하였다. 분리 효율은 기공 크기가 작을수록, 섬유가 촘촘히 배열될수록 증가하였다.