• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.458-464
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• 2006

The Pd-Ni-Ag alloy composite membrane using modified porous stainless steel (PSS) as a substrate was prepared by a electroless plating technique. In this work, we have introduced the intermediate layer between Pd-based alloy and a metal substrate. As an intermediate layer, the mixtures of nickel powder and inorganic sol such as $SiO_{2}$ sol, $Al_{2}O_{3}$ sol, and $TiO_{2}$ sol were used. The intermediate layers were coated onto a PSS substrate according to various membrane preparation conditions and then $N_{2}$ fluxes through the membranes with different intermediate layers were measured. The surface morphology of the intermediate layer in the mixture of nickel powder and inorganic sol was analyzed using scanning electron microscope (SEM). Finally, the Pd-Ni-Ag alloy composite membrane using the support coated with the mixture of nickel powder and silica as an intermediate layer was fabricated and then the gas permeances for $H_{2}$ and $N_{2}$ through the Pd-based membrane were investigated. The selectivity of $H_2/N_2$ was infinite and the $H_{2}$ flux was $1.39{\times}10^{-2}mol/m^2{\cdot}s$ at the temperature of $500^{\circ}C$ and trans-membrane pressure difference of 1 bar.

• Membrane and Water Treatment
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• v.8 no.1
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• pp.51-71
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• 2017

Antimicrobial polyethersulfone ultrafiltration membranes containing zerovalent iron ($Fe^0$) and magnetite ($Fe_3O_4$) nanoparticles were synthesized via phase inversion method using polyethersulfone (PES) as membrane material and nano-iron as nanoparticle materials. Zerovalent iron nanoparticles (nZVI) were prepared by the reduction of iron ions with borohydride applying an inert atmosphere by using $N_2$ gases. The magnetite nanoparticles (nMag) were prepared via co-precipitation method by adding a base to an aqueous mixture of $Fe^{3+}$ and $Fe^{2+}$ salts. The synthesized nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction, and dynamic light scattering analysis. Moreover, the properties of the synthesized membranes were characterized by scanning electron microscopy energy dispersive X-ray spectroscopy and atomic force microscopy. The PES membranes containing the nZVI or nMag were examined for antimicrobial characteristics. Moreover, amount of iron run away from the PES composite membranes during the dead-end filtration were tested. The results showed that the permeation flux of the composite membranes was higher than the pristine PES membrane. The membranes containing nano-iron showed good antibacterial activity against gram-negative bacteria (Escherichia coli). The composite membranes can be successfully used for the domestic wastewater filtration to reduce membrane biofouling.

• Membrane Journal
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• v.15 no.2
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• pp.114-120
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• 2005

The purpose of this study is to obtain practical information about membrane coupled $ A_2O$ system for muncipal wastewater treatment. A flat-plate microfiltration (MF) module with a pore size $0.25\;{\mu}m$ was submerged into the aeration basin and treated water was filtrated through the membrane by continuous suction with low pressure. The system was operated with synthetic wastewater to find operational parameters of internal recycle ratio and maximum MLSS showing best water quality and long-term stability. The internal recycle was defined as type 1 for aerobic to anoxic tank and type 2 for anoxic to anaerobic tank, respectively When the flux was maintained at $0.015\;m^3/m^2/hr$ (15 LMH) with 2Q type 1 internal recycle ratio, the optimal operational setting were 10 internal recycle ratio for type 2 and maximum MLSS of 11,000 mg/L among tested conditions. At this condition, removal efficiencies of BOD, CODcr, T-N and T-P showed $97.3\%,\;94.2\%,\;64.0\%,\;63.0\%$, respectively.

• Journal of Conservation Science
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• v.27 no.1
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• pp.75-90
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• 2011

At the beginning of the Chos$\breve{o}$n dynasty, punch'$\breve{o}$ng began as a simplified form of inlaid celadon, and in the two following centuries it developed into a popular folk craft in various styles and expressive decorations; overtime, it was increasingly made to resemble whiteware, and its production stopped after the Japanese invasion of Korea. In the present study, the body and glaze compositions of punch'$\breve{o}$ng were examined and compared with those of celadon and whiteware, whose compositions have previously been compared with those of Chinese ceramics. Here, the analyzed shards were organized into 28 groups based on their production sites and archaeological characteristics. For each group, the body and glaze compositions of several shards(usually three to five) were obtained, averaged, and compared with those of the other groups. These comparisons showed that the majority of the punch'$\breve{o}$ng bodies were formed, like those of celadon and whiteware, with mica-quartz porcelain stone, which was commonly used in Yuezhou, Jingdezhen, and other southern Chinese kilns. The glazes consisted of clay materials and flux components made from various proportions of wood ash, burnt limestone (glaze ash) and crushed limestone. Overall, the punch'$\breve{o}$ng glazes resembled the Kory$\breve{o}$ celadon and Kory$\breve{o}$ whiteware glazes more closely than the Chos$\breve{o}$n white wareglazes. However, the $TiO_2$ levels found in the tested punch'$\breve{o}$ng were low, similar to those of Chos$\breve{o}$n whiteware; this indicated that glaze stone was used as the clay component of the punch'$\breve{o}$ng glazes, as was the case for Chos$\breve{o}$n whiteware. This study of the material characteristics of punch'$\breve{o}$ng may be used as a comparative framework for analyzing ceramic shards discovered at current and future excavations within Korea.

• Korean Journal of Agricultural and Forest Meteorology
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• v.23 no.4
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• pp.235-250
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• 2021

The overarching question of this study is how a typical rice cultivation system in Gimje, Korea was keeping up with the triple-win challenge of climate-smart agriculture (CSA). To answer this question, we have employed (1) quantitative data from direct measurement of energy, water, carbon and information flows in and out of a rice cultivation system and (2) appropriate metrics to assess production, efficiency, GHG fluxes, and resilience. The study site was one of the Korean Network of Flux measurement (KoFlux) sites (i.e., GRK) located at Gimje, Korea, managed by National Academy of Agricultural Science, Rural Development Administration. Fluxes of energy, water, carbon dioxide (CO₂) and methane (CH₄) were directly measured using eddy-covariance technique during the growing seasons of 2011, 2012 and 2014. The production indicators include gross primary productivity (GPP), grain yield, light use efficiency (LUE), water use efficiency (WUE), and carbon uptake efficiency (CUE). The GHG mitigation was assessed with indicators such as fluxes of carbon dioxide (F_CO2), methane (F_CH4), and nitrous oxide (F_N2O). Resilience was assessed in terms of self-organization (S), using information-theoretic approach. Overall, the results demonstrated that the rice cultivation system at GRK was climate-smart in 2011 in a relative sense but failed to maintain in the following years. Resilience was high and changed little for three year. However, the apparent competing goals or trade-offs between productivity and GHG mitigation were found within individual years as well as between the years, causing difficulties in achieving the triple-win scenario. The pursuit of CSA requires for stakeholders to prioritize their goals (i.e., governance) and to practice opportune interventions (i.e., management) based on the feedback from real-time assessment of the CSA indicators (i.e., monitoring) - i.e., a purpose-driven visioneering.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.126-126
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• 2000

다이아몬드상 카본(DLC) 필름은 경도가 높고, 마찰계수가 낮다는 장점을 가지고 있기 때문에 내마모성 코팅이나 윤활성코팅에 응용을 위한 연구가 활발히 진행중이다. 하지만 마찰계수가 주변환경에 매우 큰 영향을 받는다는 단점이 있다. 이러한 단점은 DLC필름의 응용에 대한 저해 요인이 되며, 이 점을 보완하기 위해서 DLC 필름에 Si을 첨가하는 연구들이 진행되고 있다. 본 실험에서는 r.f-PACVD 법을 이용하여 Si이 첨가된 DLC 필름의 주위 환경 변화에 따른 마찰특성의 변화를 연구하였다. 사용한 반응 가스는 벤젠(C6H)과 희석된 Silane(SiH4 : H2 = 10 : 90)이며, 희석된 Silane과 벤젠의 첨가비율을 조절하여 필름내 Si의 함량을 조절하였고, 증착시 바이아스의 전압은 -400V로 하였다. 마찰테스트는 Ball-on-Disk type의 조건에서 대기, 건조공기, 진공의 세가지 분위기에서 마찰테스트를 실행하였다. 실험결과 마찰계수는 건조공기, 대기, 진공의 순으로 증가하였고, 필름내에 포함되어 있는 Si의 양이 증가할수록 마찰계수는 낮고 안정한 값을 나타내었다. Tribochemiacal 분석과, ball과 track의 전자현미경 사진 분석 결과, 진공에 비해서 건조공기와 대기중에서 마찰계수가 낮은 것은 DLC 필름내에 마모 track 중심부에 Si-C-O 계의 화합물이 형성되어, 이 화합물이 마찰계면에 존재하여 마찰계수를 낮추었음을 확인하였다. 그리고 대기중에서 실험한 경우, 습기의 존재로 인해 마모입자가 볼의 표면에서 엉김으로써 건조공기의 상태에서 보다 높은 마찰저항을 갖게 됨으로 인하여 마찰계수가 높아짐을 알 수 있었다.a)는 as-deposit 상태이며, 그림 1(b)는 45$0^{\circ}C$, 60min 열처리한 plan-view TEM 사진이다.dical의 영향을 조사하였으며 oxygen radical의 rf power에 따른 변화는 OES(Optical emission spectroscopy)를 사용하였다. 너무 적은 oxygen ion beam flux나 oxygen radical은 film의 전도도 및 투과도를 저하시켰고 반면 너무 과도한 flux의 증가 시는 전도도는 감소하였고 투과도는 증가하는 경향을 보였다. 기판에 도달하는 oxygen ion flux는 faraday cup을 이용하여 측정하였으며 증착된 ITO film은 XPS, UV-spectrometer, 4-point probe를 이용하여 분석하였다. 때문으로 생각되어진다. 또한, 성장 온도가 낮아짐에 따라 AlGaN의 성장을 저해하기 때문으로 판단된다. 성장 온도 변화에 따라 성장된 V의 구조적 특성 및 표면 거칠기 변화를 관찰하여 AlGaN의 성장 거동을 논의하겠다.034, 0.005 정도로 다시 감소하였다. 박막의 유전율은 약 35 정도의 값을 나타내었으며 X-선 회절 data로부터 분석한 박막의 변형은 증온도에 따라 7.2%에서 0.04%로 감소하였고 이 이경향은 유전손실은 감소경향과 일치하였다.는 현저하게 향상되었다. 그 원인은 SB power의 인가에 의해 활성화된 precursor 분자들이 큰 에너지를 가지고 기판에 유입되어 치밀한 박막이 형성되었기 때문으로 사료된다.을수 있었다.보았다.다.다양한 기능을 가진 신소재 제조에 있다. 또한 경제적인 측면에서도 고부가 가치의 제품

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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• pp.109-114
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• 2008

Novel green long persistent phosphors of $CaZrO_3$ : $HO_{3+}$ have been synthesized at high temperature with weak reduction atmosphere by traditional solid state reaction method. The role of $H_3BO_3$ as flux and the suitable concentration of Ho as activator on the $CaZrO_3$ : $HO_{3+}$ long persistent phosphors has been investigated. Crystals of $HO_{3+}$ doped $CaZrO_3$ long persistent phosphores were characterized by fluorescence spectrophotometer and photoluminescence (PL). The main emission spectra of 546 nm peak was revealed through synthesizing at high temperature in $N_2$ gas atmosphere. The after glow emission spectra of $CaZrO_3$ : $HO_{3+}$ long persistent phosphores arise at 546 nm peak of narrow range. because that revealed pure green color. Green long persistent phosphors have been observed in the system for over 5 h after UV irradiation (254 nm). The main emission peak was ascribed to $HO_{3+}$ ions transition from $^5F_4$, $^5S_2{\to}^5I_3$, and the after glow may be ascribed to the trap centers in the $CaZrO_3$ host lattice.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.200-209
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• 2008

Particle fluxes were measured with a time-series sediment trap from July 2003 to June 2005 at the St. KOMO(KOMO; Korea Deep-Sea Environmental Study Long-Term Monitoring Station, $10^{\circ}30'N,\;131^{\circ}20'W$) in the northeastern Pacific. Total mass fluxes at a depth of 4,960 m showed distinct seasonal variations with high values in the winter(December-February) and spring(March-May) and low values in the summer(June-August) and fall(September-November). Biogenic origin fluxes also displayed distinct seasonal variations similar to total mass fluxes. Particularly, calcium carbonate fluxes in winter and spring were more than two times greater than those in summer and fall. The prominent seasonal variations of total mass and biogenic fluxes were closely related with the seasonal changes of primary production in the surface waters; in winter and spring, primary production increased due to the enhanced supply of nutrients below the surface mixed layer by strong wind and less stratification, whereas it decreased as a result of the less supply of nutrient by reduced wind speed and strong stratification in summer and fall. The seasonal variations of total mass and biogenic fluxes in this study were higher than the differences of total mass and biogenic fluxes caused by the environmental changes such as El $Ni\tilde{n}o$ and La $Ni\tilde{n}a$ events in the previous studies. In order to understand the effects of El $Ni\tilde{n}o$ and La $Ni\tilde{n}a$ on the particle flux, therefore, the seasonal variation of particle flux in the northeastern equatorial Pacific needs to be well defined.

• Progress in Superconductivity
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• v.9 no.1
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• pp.5-10
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• 2007

We prepared four different $MgB_2$ films on $Al_2O_3$ by hybrid physical chemical vapor deposition method with thicknesses ranging from $0.65\;{\mu}m$ to $1.2\;{\mu}m$. X-ray diffraction patterns confirm that all the $MgB_2$ films are c-axis oriented perpendicular to $Al_2O_3$ substrates. The superconducting onset temperature of $MgB_2$ films were between 39.39K and 40.72K. The residual resistivity ratio of the $MgB_2$ films was in the range between 3.13 and 37.3. We measured the angle dependence of critical current density ($J_c$) and resistivity, and determined the upper critical field ($H_{c2}$) from the temperature dependence of the resistivity curves. The anisotropy ratios defined as the ratio of the $H_{c2}$ parallel to the ab-plane to that perpendicular to the ab-plane were in the range of 2.13 to 4.5 and were increased as the temperature was decreased. Some samples showed increase of $J_c$ and decrease of resistivity when a magnetic field in applied parallel to the c-axis. We interpret this angle dependence in terms of enhanced flux pinning due to columnar growth of $MgB_2$ along the c-axis.

• Journal of ILASS-Korea
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• v.22 no.2
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• pp.80-86
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• 2017

The soot formation characteristics of various alkane-based single fuel droplets were studied in this work. Also, This study was performed to provide the database of the soot behavior and formation of alkane-based single fuel droplet. The experimental conditions were set to 1.0 atm of ambient pressure ($P_{amb}$), 21% of oxygen concentration ($O_2$) and 79% of nitrogen concentration ($N_2$). Combustion and soot formation of single fuel droplet was visualized by visualization system with high speed camera. At the same time, ambient pressure, oxygen concentration and nitrogen concentration were maintained by ambient condition control system. Soot formation characteristics was analyzed and compared on the basis of intensity ratio ($I/I_0$) of background image. The results of toluene fuel droplet showed the largest soot generation. Soot volume fraction ($f_v$) was almost the same under the identical fuel types regardless of various initial droplet diameter ($d_0$) since thermophoretic flux was not much changed under the same ambient conditions.