• 멤브레인
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• 제24권5호
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• pp.375-385
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• 2014

본 연구에서는 종결정 코팅층이 NaA 제올라이트 분리막 형성에 미치는 영향에 대하여 고찰하였다. NaA 제올라이트 분리막은 평균입경 100 nm 종결정을 다공성 ${\alpha}$-알루미나 표면에 진공여과 코팅하고 $100^{\circ}C$에서 24시간 수열처리하여 합성되었다. 이때 지지체 표면에 분포된 종결정 양을 조절한 후 형성된 NaA 제올라이트 분리층의 두께와 결정입 크기 등 미세구조에 미치는 영향에 대하여 고찰하였다. 종결정 코팅 양은 지지체를 통과한 종결정 수용액의 여과 양을 조절하여 제어하였다. 종결정을 단일층으로 코팅한 후 합성하였을 경우, 코팅 양이 증가함에 따라 분리층 단면에서의 두께와 균일도는 증가하였으며, 표면에서의 결정입 크기는 감소하면서 균일도는 증가하였다. 반면, 종결정을 다층으로 코팅한 후 합성하였을 경우, 균일한 분리층을 형성하였지만 단일층으로 코팅된 경우에 비하여 불균일하였으며 두꺼운 분리층이 형성되었다. 균일하고 초박형의 결함이 없는 제올라이트 분리층을 형성하기 위해서는 종결정을 균일하고 단일층으로 코팅하여야 함을 알 수 있었다. 본 연구로부터 종결정의 코팅 상태가 이차성장에 의한 NaA 제올라이트 분리층의 미세구조를 결정하는 중요한 인자임을 확인할 수 있었다.

• 한국환경보건학회지
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• 제2권1호
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• pp.5-9
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• 1975

For analysis of Xanthene dyes according to the developing solvent and adsorbent was applied to Thin-layer chromatography with silicagel and cellulose plate. Silicagel chromato-plate used were prepared under different condition of activation. Using eight developing solvent, the influence of the condition for activation upon the separation of Xanthene dyes was investigated. The results are shown in Table 3. Methyl ethyl ketone+Acetone+$H_2O$ (10:0.1:0.4) mixture and n-butanol+Ammonia water (4:1) mixture gave clear separation for Xanthene dyes, including Fluorescein, Erythrosine Rhodamin B, Eosine, Rose bengale, phloxine and Acid red those Rf values decrease in the described ordor. Methyl ethyl ketone+Acetone+$H_2O$ (10:0.1:0.4) was applied to two adsorbents which were purchased from different manufactures. The results of Chromatograms are obtained Figure 6.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1730-1735
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• 2003

The plume-induced shock wave is a complex phenomenon, consisting of plume-induced boundary layer separation, separated shear layer, multiple shock waves, and their interactions. The knowledge base of plume interference effect on powered missiles and flight vehicles is not yet adequate to get an overall insight of the flow physics. Computational studies are performed to better understand the flow physics of the plume-induced shock and separation particularly at high plume to exit pressure ratio. Test model configurations are a simplified missile model and two rounded and porous afterbodies to simulate moderately and highly underexpanded exhaust plumes at the transonic/supersonic speeds. The result shows that the rounded afterbody and porous wall attached at the missile base can alleviate the plume-induced shock wave phenomenon, and improve the control of the missile body.

• Computers and Concrete
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• 제27권3호
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• pp.199-210
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• 2021

The aim of this paper was to examine the continuous and discontinuous contact problems between the functionally graded (FG) layer pressed with a uniformly distributed load and homogeneous half plane using an analytical method and FEM. The FG layer is made of non-homogeneous material with an isotropic stress-strain law with exponentially varying properties. It is assumed that the contact at the FG layer-half plane interface is frictionless, and only the normal tractions can be transmitted along the contacted regions. The body force of the FG layer is considered in the study. The FG layer was positioned on the homogeneous half plane without any bonds. Thus, if the external load was smaller than a certain critical value, the contact between the FG layer and half plane would be continuous. However, when the external load exceeded the critical value, there was a separation between the FG layer and half plane on the finite region, as discontinuous contact. Therefore, there have been some steps taken in this study. Firstly, an analytical solution for continuous and discontinuous contact cases of the problem has been realized using the theory of elasticity and Fourier integral transform techniques. Then, the problem modeled and two-dimensional analysis was carried out by using ANSYS package program based on FEM. Numerical results for initial separation distance and contact stress distributions between the FG layer and homogeneous half plane for continuous contact case; the start and end points of separation and contact stress distributions between the FG layer and homogeneous half plane for discontinuous contact case were provided for various dimensionless quantities including material inhomogeneity, distributed load width, the shear module ratio and load factor for both methods. The results obtained using FEM were compared with the results found using analytical formulation. It was found that the results obtained from analytical formulation were in perfect agreement with the FEM study.

• 멤브레인
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• 제22권2호
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• pp.142-154
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• 2012

DME 제조공정에서 발생하는 혼합가스 중 $CO_2$를 제거하기 위해서 $H_2$ 투과도보다 $CO_2$투과도가 우수한 고무상 고분자를 분리소재로 선정하여 복합막을 제조하고 $CO_2/H_2$의 분리성능을 검증하여 보았다. 지지체 중공사막 소재로 PEI를 이용하여 지지체 중공사막을 제조하였으며, 제조된 지지체 중공사막의 기체투과도를 각 가스별로 측정하여 PDMS의 경우는 $CO_2$ 투과도 300 GPU 이상, $CO_2/H_2$의 선택도가 4.3 이상, PEBAX를 사용한 경우 $CO_2$ 투과도 120 GPU 이상 $CO_2/H_2$의 선택도가 5 이상인 복합 중공사를 제조하였다.

• 멤브레인
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• 제6권4호
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• pp.250-257
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• 1996

글루탈알데히드와 황산을 이용하여 가교된 키토산 복합막을 제조하였다. 제조된 복합막은 글루탈알데히드와 황산용액을 이용하여 표면말을 선택적으로 가교하엿다. 제조된 키토산 막에서의 키토산과 아세트산간의 착체형성의 영향을 관찰하기 위하여 수산화나트륨으로 중화하여 성능을 비교하였다. 황산으로 표면을 가교한 경우 코팅된 활성층의 투과증발에 대한 영향을 관찰하였다. 글루탈알데히드로 가교된 키토산복합막은 지지체의 종류를 변화시키면서 투과증발성능을 비교하였다. 지지체의 순수투과성능이 증가할수록 투과유량은 비슷한 값들을 유지하였으며, 선택도는 증가하다가 다시 감소하는 경향을 나타내었다. 수산화나트륨으로 키토산을 중화시킨 경우에는 선택도는 감소하였고 투과유량은 유지되는 경향을 나타내었다. 황산을 이용하여 표면을 이온가교시킨 경우 키토산 복합막은 활성충우ㅏ 두께가 증가할수록 가교시간이 증가하여야 최적의 가교조건을 나타내었다.

• 한국전산유체공학회지
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• 제18권2호
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• pp.56-65
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• 2013

Two compression ramp problems and an impinging shock problem are computed to investigate influence of turbulence models and eddy viscosity on the shock-wave / boundary layer interaction. A Navier-Stokes boundary layer generation code was applied to the generation of inflow boundary conditions. Computational results are validated well with the experimental data and effects of turbulence models are investigated. It is shown that the behavior of turbulence (eddy) viscosity directly affects both the extent of the separation and shock-wave positions over the separation.

• 한국표면공학회지
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• 제15권2호
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• pp.69-76
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• 1982

With a view to manufacturing membranes for separation of gas mixtures, Al foils were anodized in a 2% oxalic-acid electrolyte at 40V and 80V. When anodizing was completed and Barrier layer existed at the extreme back site of the foil, the anodized foil was made to react with only electrolyte, with switching off the electric power. When the size and density of pores were changed through voltage change, the membr-anes did not show large difference in the permeability. Reacting with electrolyte, the existing Barrier layer turns into porous layer. During this process, several small pores grow from one relatively large pore, getting to the back site. The number and size of the small pores getting to the back surface increase as time passing. This change of Barrier layer into porous layer is thought to be directly related to the permeability change of the membranes. The selectivity of an anodized Al membrane was not related to the voltage change, and was high, being similar to the theoretical selctivity of metallic membranes, according to my observation.

• International Journal of Fluid Machinery and Systems
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• 제2권2호
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• pp.110-120
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• 2009

Generally the fluid flows within the centrifugal impeller passage as a decelerating flow with an adverse pressure gradient along the stream wise path. This flow tends to be in a state of instability with flow separation zones on the suction surface and on the front shroud. Hence several experimental attempts were earlier made to assess the efficacy of using boundary layer fences to trip the flow in the regions of separation and to make the flow align itself into stream wise direction so that the losses could be minimized and overall efficiency of the diffusion process in the fan could be increased. With the development of CFD, an extensive numerical whole field analysis of the effect of boundary layer fences in discrete regions of suspected separation points is possible. But it is found from the literature that there have been no significant attempts to use this tool to explore numerically the utility of the fences on the flow field. This paper attempts to explore the effect of boundary layer fences corresponding to various geometrical configurations on the impeller as well as on the diffuser. It is shown from the analysis that the fences located on the impellers near the trailing edge on pressure side and suction side improves the static pressure recovery across the fan. Fences provided at the radial mid-span on the pressure side of the diffuser vane and near the leading edge and trailing edge of the suction side of diffuser vanes also improve the static pressure recovery across the fan.

• 공업화학
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• 제29권2호
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• pp.196-200
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• 2018

본 연구에서는 복합 수소분리막 중간층의 pin hole, crack 및 defect를 최소화하기 위하여 powder type과 sol type의 금속산화물을 이용하여 복합화하였다. 중간층의 표면 형상과 투과 특성은 주사전자현미경(SEM) 분석과 $N_2$ 투과도 테스트를 통해 평가하였으며, 제조한 수소분리막의 성능평가를 위해 $N_2$와 $H_2$를 이용하여 단일가스 투과 테스트를 수행하였다. Powder type과 sol type의 금속산화물을 각각 이용하여 중간층을 적층한 결과 sol type 금속산화물을 이용하여 적층한 중간층의 표면 조도가 매우 낮았으며, 특히 $TiO_2$ sol로 형성된 중간층의 pin-hole, crack 및 defect가 현저히 감소하였다. Powder와 sol을 복합화하여 적층한 중간층은 sol로 형성된 중간층과 거의 유사한 특성을 보였으며, 이를 기반으로 제조한 수소분리막은 1 bar의 압력구배, 672 K의 온도에서 약 $0.32mol/m^2s$의 수소 투과도를 나타내었으며, 선택도는 약 10,890 이상으로 측정되었다.