• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
• /
• 2003.04a
• /
• pp.134.2-135
• /
• 2003

채소류는 생리적인 특성상 수확후 저장 및 유통되는 동안에 호흡작용, 증산작용 등의 작용이 활발해질 뿐만 아니라 곰팡이를 비롯한 식물병이 미생물의 오염 및 성장으로 부패현상을 일으키고 채소류 자체의 경도가 저하되며, 수분, 비타민, 유기산, 당분, 색소함량 등이 떨어져서 외관, 맛 신선도 등의 감소하게 된다. 본 연구에서는 채소류(오이, 호박, 방울토마토)의 선도를 연장하기 위한 저장조건을 실시하여 최적 습도 및 온도범위를 결정하였고, 이를 토대로 하여 시설채소산물을 습도조절이 가능한 원적외선 방사체 저장고(5~8$^{\circ}C$의 온도와 90% 습도유지)에 저장하면서 무처리구인 대조구와 비교하여 저장중 시료의 중량손실율, Ascorbic acid함량, 총균수(PCA사용법에 의거), pH의 변화를 측정하였고, 시료의 표면색도는 색도계(Minolta CR-300, Japan)를 사용하여 Hunter의 L, a, b값을 측정하였다. 이 결과, 채소류의 선도유지기간이 연장되는 것을 확인하였고, 중량손실율은 원적외선 방사체 저장고에 저장한 채소류가 중량손실율이 대조구에 비하여 낮게 나타났다. 따라서 습도조절이 가능한 원적외선 방사체 저장고에 채소류를 저장함으로서 채소류의 수분손실을 방지할 수 있음을 확인할 수 있었으며, 일정기간동안 원적외선 방사체 저장고에 저장함으로써 ascorbic acid함량의 감소를 대조구에 비하여 낮은 비율로 억제할 수 있었다. 총균수의 경우 채소류 시험구에서 원적외선 방사체 저장고에서 저장할수록 오염미생물의 총균수가 낮게 나타났다. 표면색도의 경우, a값은 모든 시험구에서 감소하였으며 원적외선 방사체 시험구에 비하여 대조구 저장시료의 표면색도가 청색도를 증가시키는 변화를 관찰할 수 있었고, b값은 시료간에 유의성 있는 차이없이 다소 증가하는 것으로 나타났다. 부패율은 수분 함유율이 높은 채소류일수록 원적외선 방사체 저장시설을 이용하는 경우, 부패율을 낮게 유지할 수 있었다. 따라서, 원적외선 방사체 저장시설내에 오이, 호박 및 방울토마토와 같은 채소류를 저온고습도상에서 저장할 경우, 채소류의 품질변화를 최소화 할 수 있어 갓 수확한 채소류의 선도유지기간을 연장할 수 있는 저장법이 될 수 있음을 확인하였다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.338-338
• /
• 2015

하천으로 유입되어 수질 오염을 야기하는 오염원은 오염 배출원이 명확하여 하나의 점으로 나타낼 수 있는 점오염원(Point Source)과 오염원이 명확치 않은 비점오염원(Non-point)으로 구분된다. 생활하수, 축산폐수와 같이 오염원이 명확한 점오염원은 하천 유입 이전에 처리장을 거쳐 정화작업이 가능한 반면, 비점오염원은 오염원이 명확치 않아 처리에 어려움이 따른다. 또, 오염물의 양과 이동 경로가 예측이 불가능하고 강우시에는 특별한 처리 없이 하천으로 바로 유입된다. 비점 오염원의 종류는 토사, 영양물질, 유기물질, 농약, 바이러스 등 다양하다. 이 중에서 토양에 흡착되어 이동하는 질소와 인은 하천으로 유입되어 부영양화를 야기하는 특성이 있어 더욱 처리가 필수적이다. 이러한 비점오염원으로 인한 수질 오염을 줄이기 위해 여러 최적관리기법(Best Management Practices, BMPs)이 제시되어 있으며 오염 물질의 하천 유입을 차단하는 것에 중점을 둔다. 가장 널리 이용되는 방법으로는 비점오염원 저감시설 중 하천변에 식물체를 설치하여 토양의 유실을 막는 식생대(Vegetative Filter Strip, VFS)가 있다. 식생 밀집 지역의 설치를 통해 표면 유출을 차단하고 토양 유실 감소와 수체로의 오염물질 확산을 막을 수 있다. 이에 VFSMOD-w를 이용하여 강우시 식생대를 통한 토양 유실 감소 효율에 대한 연구를 수행하였다. 연구 대상 지역으로 비교적 수문 및 토양 자료가 풍부한 청미천 유역을 선정하였다. 그 결과, 식생대의 길이와 식생대 내 식물체의 파종간격이 가장 지배적인 영향을 미치는 것이 확인된다. 이때, 식물체의 종류는 식물체 파종으로 인해 변화되는 토양의 수정된 Manning의 조도계수로 구분한다. 모든 강우 및 식물체 조건이 동일할 때, 식생대 내 식물의 파종 간격이 좁고 식생대의 길이가 길수록 토사 저감 효율이 증가하는 결과가 도출되었다. 식물체의 높이, 식물체의 종류 및 식물의 파종간격이 입력 자료로 요구되나 이 중 식물체의 높이는 토사 저감 효율에 영향을 미치지 않는 것으로 나타났다. 또, 동일한 강우 조건에서 식생대의 길이가 0.5 m에서 1.0 m로 2배 증가하였을 때 토사 저감 효율이 두 경우 모두 95% 이상의 효율을 보이는 것이 나타났다. 이는 식생대의 길이가 증가할수록 토사 저감 효율이 증가하나 일정 길이 이상이 되면 대부분의 토사가 저감되는 것을 의미한다. 결론적으로 식생의 파종 간격이 좁을수록 토사 저감 효율이 증가하더라도 식물체의 성장을 고려한 적절한 파종 간격을 선정하여야 한다. 즉, 식생대의 설치는 적절한 파종 간격 및 식생대 길이를 식생대 설치지역의 강우 특성에 따라 결정지어야 한다고 판단된다.

• Korean Journal of Optics and Photonics
• /
• v.25 no.4
• /
• pp.193-199
• /
• 2014

The net effect of the emitter orientation, Mie scatters, and pillow lenses on the outcoupling efficiency (OCE) of a bottom-emitting OLED having an internal photonic crystal layer was investigated by a combined optical simulation based on the finite-difference time-domain method (FDTD) and the ray-tracing technique. The simulation showed that when the emitter orientation was horizontal with respect to the OLED surface, the OCE could be increased by 54% when a photonic crystal layer was employed, while it could be improved by 86% under optimized conditions of Mie scatters and pillow lenses applied to the glass substrate. The peculiar intensity distribution of the OLED, caused by the periodic lattice structure of the photonic crystal layer, could be ameliorated by inserting Mie scatters into the glass substrate. This study suggests that conventional outcoupling structures combined with control of the emitter orientation could improve the OCE substantially.

• Journal of Adhesion and Interface
• /
• v.24 no.2
• /
• pp.64-68
• /
• 2023

Organic field-effect transistors (OFETs) are attracting attention in the field of next-generation electronic devices, and they can be fabricated on a flexible substrate using an organic semiconductor as a channel layer. In particular, DPP-based semiconducting conjugated polymers are actively used because they have higher charge carrier mobility than other organic semiconductors, but they are still lower than inorganic semiconductors, so various studies are being conducted to improve the charge carrier mobility. In this study, the charge carrier mobility is improved by controlling the surface energy of the substrate by forming self-assembled monolayers (SAMs). As the surface energy of the substrate is controlled by the SAMs, the crystallinity increases, thereby improving the charge carrier mobility by 14 times from 3.57×10^-3 cm²V^-1s^-1 to 5.12×10^-2 cm²V^-1s^-1

• Korean Chemical Engineering Research
• /
• v.48 no.1
• /
• pp.75-79
• /
• 2010

The precursor powders with thin wall structure were prepared by spray pyrolysis from the spray solution with ethylenediaminetetraacetic acid, citric acid and $NH_4Cl$ flux. The $BaMgAl_{10}O_{17}:Eu$ phosphor powders formed from the spray solution without organic additives and flux material had sizes of $1{\sim}5{\mu}m$ and hollow structure with high thickness at post-treatment temperature of $1,200^{\circ}C$. However, $BaMgAl_{10}O_{17}:Eu$ phosphor powders formed from the spray solution with ethylenediaminetetraacetic acid, citric acid and $NH_4Cl$ flux had fine size and plate-like shape. The mean crystallite sizes of the phosphor powders with fine sizes were 23, 35, and 33 nm when the content of $NH_4Cl$ flux were 0, 6, 35 wt% of phosphor. The photoluminescence intensity of the phosphor powders formed from the spray solution with the optimum amount of $NH_4Cl$ flux as 35 wt% was 215% of that of the phosphor powders formed from the spray solution without flux material.

• Korean Chemical Engineering Research
• /
• v.43 no.4
• /
• pp.517-524
• /
• 2005

Barium titanate ($BaTiO_3$) particles were prepared by spray pyrolysis from spray solution containing organic additives. The effects of the type and amount of organic precursors on the crystal structure and morphology of the $BaTiO_3$ particles were investigated. It was found that the morphology of $BaTiO_3$ particles before and after calcination depended on the type of organic additives such as citric acid, ethylene glycol and polyethylene glycol. Among these organic additives, citric acid was the most effective to prepare $BaTiO_3$ particles with nano-structured morphology consisting with uniform size nanometer particles after calcination. It was also found that the phase transformability of the metastable cubic phase to the tetragonal one during calcination could be improved by increasing the content of citric acid in the spray solution. As a result, $BaTiO_3$ particles prepared from spray solution containing high concentration of citric acid had good tetragonality, uniform and fine size, and high BET surface area after calcination. $BaTiO_3$ particles prepared by spray pyrolysis had nanometer size and uniform morphology after simple ball milling process.

• Polymer(Korea)
• /
• v.27 no.6
• /
• pp.549-554
• /
• 2003

Emeraldine salt of polyaniline-dodecylbenzenesulfdnic acid (PANI-DBSA) in organic solvents such as toluene and xylene was obtained by a direct one-step emulsion polymerization technique. When the molar ratio of DBSA to aniline monomer was 1.5:1, its solubility and electric property showed a maximum value and then the solid contents of PANI-DBSA was 8 wt% in toluene. The cast film of PANI-DBSA with no binder was obtained on glass or plastic substrates under ambient conditions. PANI solution can be also easily blended with polyurethane and polystyrene polymers in toluene. Improved electrical performance up to 5 S/cm was achieved with good light-transmittance up to 70% at 500 m thickness. They also showed more homogeneous morphology than that prepared with PANI-DBSA kom aqueous dispersion polymerization. The partially dispersed PANI-DBSA showed particles sizes of 50-400 m in organic solvents and their XRD pattern were observed from the powder sample.

• Journal of Applied Biological Chemistry
• /
• v.64 no.2
• /
• pp.159-164
• /
• 2021

Heavy metals exist in soils in various chemical forms including free metal ions and organo-metal complexes. The ratio of free metal ions has been known to be highly associated with the plant absorption of heavy metals. This study aims to understand the effect of free ions and organo-metal complexes on the absorption of lead (Pb) and cadmium (Cd) by plants. For this, lettuce grown in a hydroponic system for 28 days was consequently grown another 48 hours using Pb and Cd solutions. The ratios of free ion to organo-metal complexes in the solutions were adjusted at 100:0, 90:10, 70:30, 60:40 by four different organic acids (citric, oxalic, acetic, and humic acid). After that, the concentration of Pb and Cd in lettuce were analyzed. The Pb and Cd absorption by lettuce was more relied on the types of organic acids treated and the type of metals rather than the ratio of free metal ions. For example, citric acid increased the Pb absorption while it decreased the Cd absorption by lettuce. There was no significant relationship between free metal ion ratios and both Pb and Cd uptake by lettuce. It could be explained that citric acid, a relatively higher molecular weight organic acid, has higher ion binding capacity, so it forms organo-Pb complex easily due to the higher affinity of Pb on the binding site in comparison with Cd. Consequently, this complexation would assist Pb uptake by lettuce.

• Membrane Journal
• /
• v.29 no.1
• /
• pp.1-10
• /
• 2019

Poly(ether block amide) (PEBA) is one of the commercially important class of block copolymer very much suitable specifically for $CO_2$ separation. Gas separation membrane need to have good mechanical strength as well as high gas permeability. The crystalline polyamide (PA) block provides the mechanical strength while the rubbery polyether (PE) group being $CO_2$-philic facilitate $CO_2$ permeation though the membrane. Composition of thermoplastic and rubbery phase in the polymer are changed to fit into suitable gas separation application. Although PEBA has good permeability, the selectivity of the membrane can be enhanced by incorporating molecular sieve without affection much the gas permeability. Mixed matrix membrane (MMM), a class of composite membrane combine the advantage of polymer matrix with the inorganic fillers. However, there are some disadvantages based on the compatibility of the inorganic fillers and polymeric phase. This review covers both the advantage and limitations of PEBA block copolymer based composite membrane.

• Journal of Soil and Groundwater Environment
• /
• v.12 no.5
• /
• pp.115-123
• /
• 2007

Immobilization of contaminants in subsurface environment is one of the major processes that determine their fate. Especially, immobilization by oxidative-coupling reactions, which is irreversible in the bio-chemical reactions and results in a significant reduction of toxicity, can be successfully applied for the remediation of contaminated soil and groundwater more effectively than conventional degradation. As a catalyst of this oxidative-coupling reaction, manganese oxide has many advantages in practical aspects as compared to microorganisms or oxidoreductive enzymes extracted from microorganisms, fungi, or plants. This paper is to present recent research achievements on the treatment mechanisms of various organic contaminants by manganese oxide. Especially, treatment methods of non-reactive organic compounds to Mn oxide are the main focus; i.e., application of reaction mediator, PAHs treatment method, combination with an appropriate pretreatment such as reduction using $Fe^0$, which suggests the potential of a wide range of engineering application. Concerning the natural carbon cycle processes, immobilization and stabilization by oxidative coupling reaction can be effectively applied as a environmentally-friend remediation method especially for aromatic contaminants which possess a high resistance to degradation.