• Journal of the Korea Organic Resources Recycling Association
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• v.20 no.3
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• pp.71-82
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• 2012

Common bulking agents in composting system include woody materials such as sawdust and woodchips. These bulking agents are mainly used for the purpose of the proper control of C/N ratio and moisture content in the composting. The topic for the effect on air permeability of bulking agents has far received relatively little attention in the composting field. This study investigated the effect of bulk density, moisture content, air-filled porosity, particle size and air flow rate on air permeability of several mixture ratios of sawdust and woodchip bulking agent. Increasing the moisture contents, the air-filled porosity was decreased and the particle size was increased for all kinds of bulking agent mixtures. Especially, with the increasing of mixing ratio of woodchip, these effects were sharply magnified. The air permeability respond to air-filled porosity was very similar to that for moisture content which was anticipated the linear relationship between air-filled porosity and moisture content. Above the region of moisture content 0.25 or 0.43(d.b.)(20 or 30% w.b.), the pressure drop decreased even though air-filled pore spaces were filling with water. Especially, to the particle size of 5 mm the pressure drop was decreased exponentially, so the air permeability was dramatically improved. By the water had the role of binding of the small particles, the macropores less resistances to air flow were created in the matrix. The effect of particle size on air permeability was much stronger than that of air-filled porosity or moisture content. And it is needed the preparing of initial particle size above 5 mm for efficient composting.

• Polymer(Korea)
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• v.34 no.1
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• pp.1-7
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• 2010

To enhance the transport properties of gas separation membrane, we prepared 6FDA-6FpDA based polyimide membrane with PMMA-graft-silica nanoparticles. The silica was grafted PMMA which is miscible with 6FDA-based polyimide after surface treatment by 3-methacryloxypropyltrimethoxysilane ($\gamma$-MPS). The untreated silica/6FDA-6FpDA membrane showed greater permeability and less selectivity than PMMA-g-silica/6FDA-6FpDA due to its low dispersion. The transport properties of PMMA-g-silica/6FDA-GFpDA membrane were measured as a function of filler concentration. These membranes were evaluated using pure gases (He, $O_2$, $N_2$, $CO_2$). The increase in permeation was attributed to changes in the free volume distribution until 1 wt%. After 1 wt%, the permeability was decreased by excess silica which decreased effective area in polymer matrix. The selectivity was decreased with increasing permeability on the whole. However, the selectivity of $CO_2$ showed more enhance value.

• Applied Microscopy
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• v.20 no.2
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• pp.81-101
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• 1990

Toad bladder의 상피수송(上皮輸送)을 분석(分析)하기 위하여 동결치환(凍結置換) 및 동결절단법(凍結切斷法)을 적용(適用)하여 전자현미경(電子顯微鏡) 관찰(觀察)을 실시하였다. 방광(膀胱)의 점막층(粘膜層)은 과립성세포(顆粒性細胞), 미토콘드리아가 풍부한 세포, 점막분필세포(粘膜分泌細胞) 및 기저세포(基底細胞)등 4가지 세포로 구성되어 있었다. 과립성세포(顆粒性細胞)는 점막표면적의 대부분을 점유하며 $Na^+$ 수송(輸送)에 주요한 역할을 하고, 정단부(頂端部)의 세포질에는 다수의 과립이 분포하며 정단세포막(頂端細胞膜)은 microvilli type I로 배열되어 있고, 표면에 glycoprotein을 함유하는 세포외막(細胞外膜)이 관찰되었다. 대조적으로 미토콘드리아가 풍부한 세포는 세포질 전역에 걸쳐 다수의 미토콘드리아가 분포해 있으며 주요 기능은 $H^{+},\;K^{+}$ 및 $HCO_{3}^{-}$ 분필수송(分泌輸送)에 관여할 것으로 생각되며 이들 수송상피(輸送上皮)는 정단부가 견고연접(堅固連接)으로 둘러 싸이고 기저세포막(基底細胞膜)은 인접세포와 서로 분리되므로 상피세포의 극성이 유지되며 정단부(頂端部) 세포막과 기저세포막의 수송특성(輸送特性)은 각기 다르다고 생각된다. 따라서 두꺼비 방광(膀胱)에서 상피수송(上皮輸送)은 세포 통과수송 및 세포간 분류수송 경로를 나타내고 있다. 한편 세포막 투과성(透過性)의 조절과 관련하여 동결절단(凍結切斷) 전자현미경 관찰에 의하면 forskolin에 촉진된 정단부(頂端部) 세포막 투과성의 변화는 세포막내(細胞膜內) 입자(粒子)의 분포와 밀접한 관계를 가지는 것으로 보인다. 특히 과립성세포(顆粒性細胞)에서 집단으로 관찰되는 세포막내(細胞膜內) 입자(粒子)는 forskolin에 유도된 정단세포막(頂端細胞膜) 투과성의 변화를 나타내주는 것으로 사료되나 이의 기능적 의미에 대하여는 연구가 더욱 필요하다고 본다.

• Journal of the Korean Magnetics Society
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• v.13 no.2
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• pp.59-63
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• 2003

Superparamagnetic properties of self-aggregated cobalt nanoparticles in the perfluorinated ion-exchange polymeric membrane (MF-4SK) prepared by ion-exchange and recovery methods were investigated by transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID) magnetometer at various temperatures. Our experimental results show that cobalt nanoparticles in MF-4SK for the concentration of $7.8{\times}10^{19}$ atoms per 1 g of polymer membrane exhibit superparamagnetic properties above the average blocking temperature ($T_{B}$), which is determined to be around 185 K at applied field of 500 Oe. The average particle radius of 4.0 nm achieved from Langevin function fit is in good agreement with TEM observations. This experimental evidence suggests that cobalt nanoparticles in polymer film obey a single domain theory. The results are discussed in the light of current theory for the superparamagnetic behavior of magnetic nanoparticles.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.6
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• pp.613-619
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• 2006

The objectives of this research are to evaluate the effect of membrane materials, particulate matter and membrane pore size on permeate flux. It was shown that the removal efficiency of high MW organic matter more than 10 kDa was lower than that of low MW organic matter for $MIEX^{(R)}$ process. For the change of permeate flux by the pretreatment process, $MIEX^{(R)}+UF$ process showed high removal efficiency of organic matter as compared with coagulation+UF processes, but high reduction rate of permeate flux was presented through the reduction of removal efficiency of high MW organic matter. The pretreatment of the raw water significantly reduced the fouling of the hydrophilic membrane, but did not decrease the flux reduction of the hydrophobic membrane. Flux decline on MF process increased due to the pore clogging, while the permeate flux decline of UF process decreased due to the formation of cake layer. It was shown that particle matter was not effect on MIEX+membrane process. But, for coagulation+membrane process, particle matter was important factor on permeate flux.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.161-167
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• 2008

Using an experimental method named filtration-permeation, the influence of sedimentation during filtration was studied for the suspensions composed of particles and that of flocs. The average specific cake resistances measured by filtration do not give accurate values because of the sedimentations during filtration, but the permeation data give quite accurate values. The prolonged permeation rates for the cake formed from particulate suspension do not change, but that rate from the floc filtration changes by the sweeping of flocculant. It is proposed that the cake compressibility can be measured with one set of filtration-permeation experiment by step increase of pressure during permeation period. The another experimental method which can shorten experimental time for floc filtration using filtrationpermeation is also proposed.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.31.1-31.1
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• 2011

현재 발광 소자, 태양전지, 디스플레이 등의 산업 분야에서는 저반사 나노 패턴, 광결정 패턴, 초소수성 나노 구조 등을 적용하여 소자의 효율을 향상시키기 위한 연구가 진행되고 있다. 하지만 이러한 기능성 패턴 제작을 위해서는 기능성 소재의 증착, 노광 공정, 식각 등의 복잡하고 고가인 공정이 필요하기 때문에 실제 적용이 어려운 한계가 있다. 이에 본 연구에서는 나노 입자가 분산된 레진을 직접 임프린팅하는 저비용의 간단한 공정으로 나노 크기에서 마이크론 크기에 이르는 다양한 기능성 패턴을 제작하였다. 구체적으로, ZnO 나노 입자를 PMMA 레진에 분산하여 나노 입자 솔루션을 제작하였고 열경화 임프린트 공정을 통해서 Si 및 글래스 기판 위에 micron 및 sub-micron 급의 격자 패턴을 형성하였다. 이후 레진에 포함되는 ZnO 나노 입자 함량비에 따른 굴절률 및 투과도와 표면 거칠기에 따른 접촉각 측정을 통해서 기능성 패턴의 광학특성 및 표면특성을 분석하였다.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.47 no.2
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• pp.179-184
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• 2021

Stratum corneum known as a skin barrier, which maintains water in skin, is the outer layer of the skin. Natural moisturizing factors (NMF) are one of the constituents in stratum corneum and amino acids are the highest components among NMF. In this study, we designed stearic acid-based solid lipid nanoparticles (SLNs) for improved skin penetration of serine (Ser). Ser-capsulated SLN was manufactured by double-melting emulsification method. The mean particle size and zeta potential of SLNs were 256.30 ~ 416.93 nm and -17.60 ~ -35.27 mV, respectively. The higher the degree of hydrophobicity or hydrophilicity of emulsifiers, the smaller the particle size and the higher the stability and capsulation rate. In addition, skin penetration was conducted using SkinEthic^TM RHE which is one of the reconstructed human epidermis models. The results of Ser penetration demonstrated that all SLNs enhanced than serine solution. The amount of enhanced Ser penetration from SLNs were approximately 4.1 ~ 6.2 times higher than that from Ser solution. Therefore, Ser-loaded SLN might be a promising drug delivery system for moisturizing formulation in cosmeceutical.

• Journal of Plant Biology
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• v.35 no.3
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• pp.259-263
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• 1992

한국 마늘에 감염되어 있는 주된 바이러스 중의 하나로 알려진 마늘 잠복 바이러스 (GMV)의 분자 구조와 병 발생 메카니즘을 이해하기 위하여, 국부 감염 숙주 식물인 Vicia faba에 연속적으로 감염시킴으로써 마늘 잠복 바이러스를 정제하였고, GMV에 대한 전신 감염성 숙주 식물로 생각되는 leek에서 GLV를 대량으로 증식시켰다. 투과전자현미경을 이용하여 바이러스 입자를 관찰한 결과, 마늘 바이러스들의 입자의 길이는 200-2000 nm의 분포를 보였으나 입자의 대부분은 600-900 nm의 범위 안에 존재하였다. 반면 순수 분리된 GLV 입자는 평균 690 nm의 길이를 보여주었고, 유연한 실 모양이었다. SDS-PAGE 분석으로 혼합 감염된 마늘 잎으로부터 분리된 마늘 바이러스의 구조 단백질은 분자량 24,500-38,000 Da의 분포를 나타내었으나, GLV 껍질 단백질의 분자량은 34,000 Da으로 나타났다.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.1
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• pp.82-86
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• 2001

The aim of this study was to investigate the level of radiopacity of esthetic dental restorative materials and determine the optimum level of radiopacity in pediatric dentistry. Disks of 8 dental restorative material groups as the experimental group, 7mm in diameter and 2mm thick, were radiographed with intact human deciduous teeth and aluminum stepwedge standard. Radiopacity was evaluated with an image analysis program following the digitization of the radiographs using a flatbed scanner with transparency unit. All materials and tooth structure also the significant difference except FP, VB, VM. For the radiopacity of esthetic restorative dental materials to exceed that of enamel, it should be greater than 1.7mm of equivalent thickness of aluminum.