• Proceedings of the Membrane Society of Korea Conference
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• 1994.10a
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• pp.36-37
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• 1994

Sirkar등[1]이 많이 연구한 hollow-fiber contained liquid membrane방식보다 막내부에서의 물질전달 저항을 크게 낮출 수 있는 이른바 flowing liquid membrane방법을 Teramoto등[2]은 제안하였다. 좀더 발전된 membrane absorber방식으로서 평판형(flat-sheet type)막으로 흡수(absorption) 및 탈착(desorption)모듈을 구성하고, monoethanolamine 흡수제(absorbent)로 $Co_2/CH_4$ 분리에 적용하여 선택도를 크게 향상시킨 기존의 실험결과도 볼 수 있다. 막에서의 기-후 접촉과 반응이 수반된 물질전달에 의한 기체흡수 현상에 관해 많은 이론해석과 실험결과가 연구된 바 있다. 본 연구에서는 이산화탄소와 같은 산성기체(acid gas)의 분리에 주로 적용될 새로운 방식의 순환식 중공사막 흡수기 (circulatory hollow-fiber membrane absorber: HFMA)를 제안하고 이의 실제적용에 대한 기초로서 모델해석에 의한 분리성능을 예측하였다.

• Journal of Astronomy and Space Sciences
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• v.36 no.1
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• pp.1-9
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• 2019

In this paper we present analysis of current density when the Cluster spacecraft pass the nightside auroral region at about $4-5R_E$ from the center of Earth. The analysis is made when the inter-spacecraft separation is within 200 km, which allows all four spacecraft to be situated inside the same current sheet. On 22 February 2002, two field-aligned current (FAC) events were observed in both the southern and the northern hemispheres. The FACs were calculated with magnetic field data obtained by the four spacecraft using the Curlometer method. The scales of the FACs along the spacecraft trajectory and the magnitudes were hundreds of kilometers and tens of $nA/m^2$, respectively, and both events were mapped to the auroral region in the ionosphere. We also examined reliability of the results with some parameters, and found that our results are adequately comparable with other studies. Nevertheless, some limitations that decrease the accuracy of current estimation exist.

• Journal of the Mineralogical Society of Korea
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• v.28 no.2
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• pp.127-133
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• 2015

Li-bearing muscovite is commonly found along with trioctahedral lepidolite in granitic pegmatites. Structurally, $Li^+$ ions can replace $K^+$ ions in the interlayer (Int) of muscovite or incorporate into vacancies of the dioctahedral sheet (Sub). However, detailed mechanism of the lithium incorporation into muscovite is challenging to investigate using experimental techniques alone. In the current study, density functional theory (DFT) has been applied to examine the crystal structure and energy variation when $Li^+$ resides in the interlayer or the octahedral sheet. Depending on the position of $Li^+$ (i.e., Int vs. Sub), DFT showed significant differences in the mica's structures such as lattice parameters, sheet thickness, interlayer separation, and OH angles with respect to the ab plane. DFT further showed that, in pure muscovite, $Li^+$ has a lower energy when it is located in Int than Sub. By contrast, in the case of $Fe^{2+}$ substitution into the octahedral sheet, $Li^+$ has a lower energy in Sub than in Int. These results imply that $Li^+$ incorporates into the Al octahedral sheets only when the octahedral sheets possess structural charges, suggesting cation substitution in the octahedral sheets plays an important role in the Li incorporation mechanism into muscovite. They can also explain the experimental observation about the positive relationship between $Fe^{2+}$ and $Li^+$ amounts in Li-bearing muscovite.

• Membrane Journal
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• v.23 no.4
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• pp.257-266
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• 2013

The main purpose of this study is to develop a commercial scale of pervaporative process equipped with hollow fiber membrane modules, being able to effectually purify organic solvent at high temperature well over its boiling point under high vapor pressure. Three constituent technologies have been developed; 1) to fabricate braid-reinforced hollow fiber membrane stable in high pressure and high temperature application, 2) to design and fabricate a commercial scale of hollow fiber membrane module, and 3) to design and fabricate a pilot scale of pervaporation equipment system. The developed hollow fiber membrane possesses a membrane performance superior to the membrane of Sulzer (Germany) which is the most-well known for pervaporation process, and the membrane module equips hollow fiber membranes of $4.6m^2$ and the pervaporation system can treat organic liquid at 200 L/h, which is based on the dehydration of 95 wt% isopropyl alcohol (IPA). Since the membrane module is designed to flow in and pass through the inside of individual hollow fiber membrane, not to involve both the formation of feed's dead volume observed in flat-sheet membrane module and the channeling of feed occurring inside hollow fiber bundle which lower membrane performance seriously, it showed excellent separation efficiency. In particular, the module is inexpensive and has less heat loss into its surrounding, in compared with flat-sheet membrane module. In addition, permeant can be removed effectively from the outer surface of hollow fiber membrane because the applied vacuum is conveyed uniformly through space between fibers into respective fiber, even into one in the middle of the hollow fiber bundle in which the space between fibers is uniform in distance. Since the hollow fiber membrane pervaporation system is the first one ever developed in the world, our own unique proprietary technology can be secured, preoccupying technical superiority in export competitive challenges.

• Membrane Journal
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• v.5 no.1
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• pp.35-43
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• 1995

For several years lots of attempts have been made to establish the liquid membrane-based techniques for separations of gas mixtures especially containing carbon dioxide. A more effective system to separate $CO_{2}$ from flue gases, a circulatory hollow-fiber membrane absorber(HFMA) consisting of absorption and desorption modules with vacuum mode, has been considered in this study. Gas-liquid mass transfer has been modeled on a membrane module with non-wetted hollow-fibers in the laminar flow regime. The influence of an absorbent flow rate on the separation performance of the circulatory HFMA can be predicted quantitatively by obtaining the $CO_{2}$ concentration profile in a tube side. The system of $CO_{2}/N_{2}$ binary gas mixture has been studied using pure water as an(inert) absorbent. As the absorbent flow rate is increased, the permeation flux(i.e., defined as permeation rate/membrane contact area) also increases. The enhanced selectivity compared to the previous results, on the other hand, shows the decreasing behavior. It has been found obviously that the permeation flux depends on the variations of pressure in gas phase of desorption module. From an accurate comparison with the results of conventional flat sheet membrane module, the advantageous permeability of this circulatory HFMA can be clearly ascertained as expected. Our efforts to the theoretical model will provide the basic analysis on the circulatory HFMA technique for a better design and process.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.177-186
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• 1999

The purpose of this study is to analyze the interface debonding of RC beams strengthened by carbon fiber sheet(CFS). The behavior of damaged RC beams strengthened with CFS is analytically investigated next using linear elastic fracture mechanics(LEFM) approach and the finite element method. The study includes an investigation of the separation mode by interface fracture of the strengthening materials due to the interfacial shear and normal stresses. The numerical method is presented to obtain the value of interfacial fracture parameter such as the strain energy release rate. Based on the results of this study, it is found that the critical case occurs when the interfacial cracks occur within a short region of the flexural crack. The CFS strengthening has not an adequate factor of safety against interfacial debonding of CFS. Furthermore, for the thicknesses of the adhesive studied[1mm~3mm], it is no noticeable effect on the strain energy release rate.

• Composites Research
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• v.29 no.4
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• pp.203-208
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• 2016

Metal and polymer sandwich composites, which are made of sheet metal sheath and polymer or fiber reinforced plastic core, have been reconsidered as an alternative to sheet metal due to their lightness and multifunctional properties such as damping and sound-proof properties. For the successful applications of these composites, the delamination prediction based on the adhesion strength is important element. In this study, the numerical simulation of the delamination behavior of polymeric adhesive tapes with metallic surfaces was performed using cohesive zone elements and finite element software. The traction-separation law of the cohesive zone element was defined using the fracture energy derived from peel mechanics and experimental results from peel test and implemented in finite element software. The peel test of the polymeric adhesive film against steel surface was simulated and compared with experiments, demonstrating reasonable agreement between simulation and experiment.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.29-33
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• 2005

In order to recycle the waste material and to develop the thickening unit of waste activated sludge from wastewater treatment facilities, the filtration bio-reactor equipped with a shadow mask filter module was employed for this work from which the operating properties and parameters were drawn. The sludge thickening and filtration unit is made of cylindrical acryl tank(12cm i.d. ${\times}$ 58cm height: working volume of 6L), where the flat-sheet type of shadow mask filter module(pore size: 220~250um, opening area: 34.8~39.6%) was installed and the effluent was withdrawn from the effluent port at the lowest point of the reactor, and the filtration was performed only by the hydraulic pressure. For evaluating the operating performance of this reactor, some parameters such as the solid-liquid separation of different biomass concentrations, the water quality of filtrate, the aeration cleaning time and the cleaning effect were investigated. Depending on the MLSS concentrations, the different time to withdraw 3L of filtrate was required in which the longer filtration time was necessary for the higher MLSS concentrations caused by the thicker formation of cake layer: 40 minutes for 5,000 mg/L, 70 minutes for 10,000 mg/L and 100 minutes for 15,000 mg/L, where the concentrations of SS were 8.9, 6.7 and 6.5 mg/L, respectively. Under the same operating conditions (the intensity of aeration cleaning: 80 L/min, MLSS: 10,000 mg/L), the proper aeration cleaning time was revealed 30 seconds, and the stable formation of cake layer was in the range of 10 to 15 minutes. Therefore, the shadow mask considered as a waste material can be of use as a filter material for the sludge thickening system.

• Transactions of Materials Processing
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• v.24 no.1
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• pp.37-43
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• 2015

The purpose of the current study is to improve the clinching joint strength of aluminum and fiber metal laminates (FMLs) comprised of three layers. The joining of FML and Al 5052 by a conventional clinching joint has some disadvantages such as necking of the upper sheet, lack of interlocking, defects caused by the vertical load, and especially loss of strength of the composite material due to the low ductility. In the current study, a tapered-hole clinching method is proposed as an alternative for the joining of Al 5052 and FMLs. A hole with a tapered shape is formed before the joining process. The design parameters were evaluated using the Taguchi method for the geometry of the tapered hole in order to determine the maximum separation load. The diameter of the punch corner, clearance, punch stroke and the tapered length were used as the main variables in the Taguchi method. In conclusion, the contribution ratio for each of the fours variable examined was 35.07%, 22.44%, 21.32% and 14.11%, respectively. In addition, the appropriate combination of the design parameters can make a 5% improvement in the vertical direction joint strength.

• Membrane and Water Treatment
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• v.6 no.3
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• pp.237-249
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• 2015

In this study we investigate a laboratory scale vacuum membrane distillation system to produce pure water from model oil in water emulsion. Experimental determination of liquid entry pressure (LEP) of a commercial Durapore$^{TM}$ GVPH flat sheet membrane using model emulsions in various oil concentrations has been carried out. Two different methods of liquid entry pressure determination - a frequently used, so-called static and a novel dynamic method - have been investigated. In case of static method, LEP value was found to be 2.3 bar. No significant effect of oil content on LEP was detected up to 3200 ppm. In contrast, LEP values determined with dynamic method showed strong dependence on the oil concentration of the feed and decreased from 2.0 bar to a spontaneous wetting at 0.2 bar in the range 0-250 ppm, respectively. Vacuum membrane distillation tests were also performed. The separation performance is evaluated in terms of flux behavior, total organic carbon removal and droplet size distribution of the feed and final retentate. No significant effect of oil content on the flux was found ($5.05{\pm}0.31kgm^{-2}h^{-1}$) up to 250 ppm, where a spontaneous wetting occurred. High separation performance was achieved along with the increasing oil concentration between 93.4-97.0%.