• Membrane and Water Treatment
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• 제7권2호
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• pp.101-113
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• 2016

In this study, to improve the water flux of porous hydrophobic membranes, various water-soluble polymers including neutral, cationic and anionic polymers were adsorbed using 'salting-out' method. The adsorbed hydrophobic membrane surfaces were characterized mainly via the measurements of contact angles and scanning electron microscopy (SEM) images. To enhance the durability of the modified membranes, the water-soluble polymers such poly(vinyl alcohol) (PVA) were crosslinked with glutaraldehyde (GA) and found to be resistant for more than 2 months in vigorously stirred water. The water flux was much more increased when the ionic polymers used as the coating materials rather than the neutral polymer and in this case, about 70% of $0.31L/m^2{\cdot}h$ (LMH) to 0.50 LMH was increased when 300 mg/L of polyacrylamide (PAAm) was used as the coating agents. Among the cationic coating polymers such as poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA), poly(acrylic acid-comaleic acid) (PAM) and poly(acrylic acid) (PAA), PSSA_MA was found to be the best in terms of contact angle and water flux. In the case of PSSA_MA, the water flux was enhanced about 80%. The low concentration of the coating solution was better to hydrophilize while the high concentration inclined to block the pores on the membrane surfaces. The best coating condition was found: (1) coating concentration 150 to 300 mg/L, (2) ionic strength 0.15, (3) coating time 20 min.

• Membrane and Water Treatment
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• 제8권5호
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• pp.449-462
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• 2017

Direct treatment of municipal wastewater by forward osmosis (FO) process was evaluated in terms of water flux decline, reverse salt diffusion, pollutants rejection and concentration efficiency by using synthetic seawater as the draw solution. It was found that when operating in PRO mode (active layer facing the draw solution), although the FO membrane exhibited higher osmotic water flux, more severe flux decline and reverse salt diffusion was also observed due to the more severe fouling of pollutants in the membrane support layer and accompanied fouling enhanced concentration polarization. In addition, although the water flux decline was shown to be lower for the FO mode (active layer facing the feed solution), irreversible membrane fouling was identified in both PRO and FO modes as the water flux cannot be restored to the initial value by physical flushing, highlighting the necessity of chemical cleaning in long-term operation. During the 7 cycles of filtration conducted in the experiments, the FO membrane exhibited considerably high rejection for TOC, COD, TP and $NH_4{^+}-N$ present in the wastewater. By optimizing the volume ratio of seawater draw solution/wastewater feed solution, a concentration factor of 3.1 and 3.7 was obtained for the FO and PRO modes, respectively. The results demonstrated the validity of the FO process for direct treatment of municipal wastewater by using seawater as the draw solution, while facilitating the subsequent utilization of concentrated wastewater for bioenergy production, which may have special implications for the coastline areas.

• 멤브레인
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• 제19권4호
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• pp.285-290
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• 2009

공칭 세공크기 $0.1\;{\mu}m$이고 내경이 5 mm인 정밀여과용 관형 분리막 내에 자체 설계한 배출봉을 삽입하여 막오염 감소효과에 따른 투과유속을 측정하였다. 원료용액으로는 에멀젼 상태의 dioctyl tinoxide (DOTO) 입자를 사용하였으며 0.5 wt%까지 농도를 변화시키면서 1.6 bar 이내에서 운전하였다. 배출봉의 효과는 매 실험마다 배출봉을 삽입한 경우와 사용하지 않은 경우의 투과유속을 비교하여 평가하였다. 배출봉을 사용할 경우 운전압력 1.6 bar에서 최대 20%의 투과유속이 향상되었다. 또한 DOTO 농도가 증가함에 따라서 배출봉에 의한 투과유속 향상효과는 크게 나타났으며 0.5 wt% 농도에서 43%까지 투과유속이 향상되었다.

• 한국물환경학회지
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• 제21권3호
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• pp.242-247
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• 2005

In this study, we investigated the removal efficiencies of pollutants and permeate fluxes depending on chemistry of feed water, various molecular weight cut-offs (MWCOs) and materials of membrane, operating pressure. We used seven MWCO membranes of YC0.5, YM1, YM3, YM10, YM30, YM100 and PM30, humic acid solution and surface water as feed water, and examined variation in permeate flux. Results of TOC removal experiment demonstrate that MWCO lower 1,000daltons could remove humic acid effectively. As increasing solution pH and decreasing divalent cations ($Ca^{2+}$) concentration, TOC removal increased. But $UV_{254}$ removal efficiency increased with higher divalent cation concentration and solution pH. Membrane fouling increased with increasing electrolyte (NaCl), divalent cation concentration and decreasing solution pH. In spite of initial permeate flux of the hydrophobic membrane (PM30) was higher than that of the hydrophilic membrane (YM30), flux decline of PM30 was significant during operation. At higher operating pressure, compactness of the cake layer on the membrane surface increased, resulting in gradual increase in hydraulic resistance.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.274-279
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• 2012

Daegu Solar Power Tower Plant of 200 kW thermal capacity was developed for the first time in Korea, 2011. Measurement of the heat flux distribution is essential to evaluate the solar energy concentrated by reflectors and to design a suitable receiver. The flux mapping technique, which uses a radiometer and a diffuse plate, is common for measurement of the heat flux distribution. Because the solar power tower plant has a wide concentration area, the flux mapping technique using a fixed diffuse plate is difficult to apply. Therefore, the flux distribution in the solar power tower plant should be measured by the flux mapping technique using a small moving bar. In this study, we measured flux distributions with the moving-bar system developed at the KIER solar furnace and evaluated its applicability for the solar power tower plant.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1324-1329
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• 2018

This study presents a practical application of complementary safety indicators, which can be applied in a safety assessment of a radioactive waste repository by excluding a biosphere simulation and comparing the artificial radiation originating from the repository with the background natural radiation. Complementary safety indicators (radiotoxicity flux from geosphere and radiotoxicity concentration in seawater) were applied in the safety assessment of a rock-cavern type low and intermediate level radioactive waste (LILW) repository in the Republic of Korea. The natural radionuclide ($^{40}K$, $^{226,228}Ra$, $^{232}Th$, and $^{234,235,238}U$) concentrations in the groundwater and seawater at the Gyeongju LILW repository site were measured. Based on the analyzed concentrations of natural radionuclides, the levels of natural radiation were determined to be $8.6{\times}10^{-5}$ - $8.0{\times}10^{-4}Sv/m^2/yr$ and $6.95{\times}10^{-5}Sv/m^3$ for radiotoxicity flux from the geosphere and radiotoxicity concentration in seawater, respectively. From simulation results obtained using a Goldsim-based safety assessment model, it was determined that the radiotoxicity of radionuclides released from the repository is lower than that of the natural radionuclides inherently present in the natural waters. The applicability of the complementary safety indicators to the safety case was discussed with regard to reduction of the uncertainty associated with biosphere simulations, and communication with the public.

• Journal of Pharmaceutical Investigation
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• 제35권2호
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• pp.81-87
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• 2005

We have prepared karaya gum patches containing ketoprofen and investigated the effect of short-time current pretreatment of skin on the permeability. Hairless mouse skin was treated with current before the patch was mounted on the skin. The effect of current density and current duration on the flux of ketoprofen was studied. The possibility of additive effect with penetration enhancer (PGML) was also investigated. Iontophoretic pretreatment of skin increased the passive flux up to 3 folds at 0.4 $mA/cm^2$ current density, when the matrix contained no PGML. As the duration of current-pretreatment and current density increased, flux increased. PGML increased the average passive flux markedly, about 6 to 12 folds, depending on the concentration in the patch. Current pretreatment further increased the flux from this PGML containing patch, exhibiting additive effect. These results indicate that short-duration current pretreatment of skin can be an useful method for the enhancement of ketoprofen permeability through skin.

• Journal of Magnetics
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• 제16권1호
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• pp.58-63
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• 2011

This paper presents design procedures of a transverse flux linear motor (TFLM). The minimum and maximum flux linkage was determined by the simplified equivalent magnetic circuit and estimated average magnetic flux density at the air gap region by considering the shape of applied magnetomotive force (MMF). With this information, the number of turns of each phase winding was calculated based on the amplitude of applied voltage and speed of a mover. The rated current, coil diameter, and winding area were obtained with the aid of an empirical formula for determining the required MMF. The usefulness of the proposed design method for TFLM is verified by the three-dimensional equivalent magnetic circuit network (EMCN) method and the experimental results of prototyped machine.

• 설비공학논문집
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• 제22권10호
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• pp.704-709
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• 2010

The effect of oil on flow boiling of R-123 in a plain tube bundles was experimentally investigated for a range of quality and heat flux. It is shown that the heat transfer coefficient decreased as the oil concentration increased. Comparison with the previous pool boiling data reveals that the reduction of heat transfer coefficient by oil is more pronounced in pool boiling, and the difference increased with the increase of oil concentration and heat flux. Within the experimental range, the variation of mass flux or quality has negligible effect on the heat transfer coefficient.

• Journal of Electrical Engineering and Technology
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• 제7권3호
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• pp.342-348
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• 2012

This paper presents a moving-magnet type linear actuator designed by using flux concentration type permanent magnet arrangement, which can generate higher magnetic flux density in air-gap. In this construction, detent force which is induced by both slot-effect and end-effect becomes larger due to strong attractive forces. To reduce cogging force we have employed a modular mover structure of two magnetic pole sections connected with a center yoke. The improved motor performance is demonstrated with the prototype machine.