• Clean Technology
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• v.18 no.2
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• pp.123-143
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• 2012

Supercritical fluid technology (SFT) is recently one of the most new techniques, which has been interested various fields of related chemical industries. SFT is the most effective and practical technology with eco-friendly, energy-savings, and high efficiency as the technique using the advantages of supercritical fluid such as high solvation power, solubility, mass transfer rate, and diffusion rate. Especially, it is necessary to analyze, evaluate, and develop the potential of application techniques using SFT with these characterizations. Therefore in this review, the phase behavior in supercritical fluid at high temperature and pressure of monomers/polymers for the optimization of polymerization process are briefly described, and the preparation of molecularly imprinted polymers (MIPs) in supercritical fluid using supercritical polymerization and the performance evaluation of MIPs are introduced.

• Journal of the Korean association of regional geographers
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• v.13 no.5
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• pp.477-494
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• 2007

This paper offers a brief overview of the historical implications of residential segregation in Busan, Korea. It first reviews the history of residence from the early 1900s to the present and the transition of residential boundary of the City of Busan. It then considers the characteristics of residential segregation and the important factors in it. The social class of pre-industrial society led the inequality of residential areas around the Eubchee. The existed Korean residential areas were separated by newly built-up residential areas in the Japanese colonial era. After the liberation from Japanese Rule and Korean War, rapid population growth made considerable slums across the City of Busan. These slums were an important factor to segregate residential areas from prosperous areas ever afterward. The socio-economic status has related to residential segregation through the formation of differential housing classes since 1990s. The historial analysis of these periods will offer an insight into how the dominant factors lead residential segregation in a specific period by promoting a more socio-economically integrated society.

• Journal of the Korean Chemical Society
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• v.53 no.5
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• pp.585-608
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• 2009

The aim of this study was to research the characteristics of science teachers' thinking related to dissolution and diffusion. For this study, five science teachers who majored in chemistry or chemistry education were selected and interviewed. These teachers have been teaching on average for 2$\sim$6 years. From the study, it was discovered that the science teachers didn't recognize the necessity of sorting out diffusion from dissolution. The teachers divided in various mixing phenomena with diverse criteria. The science teachers had difficulty in sorting out diffusion from dissolution based on solubility and Gibbs' energy. The teachers didn't see the linkage between the contents that were divided into chapters, and didn't find omitted contents themselves in the chapters that introduced applicable principles. During the interviews, the teachers felt the need to understand the principles for understanding phenomena. But they did not have the ability to teach these principles after learning about the principles themselves. Therefore, it is necessary to develop teacher education programs, as well as a science curriculum, that helps in linking the knowledge between natural phenomena and principles.

• Membrane Journal
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• v.27 no.5
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• pp.389-398
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• 2017

The most important characteristic of the polymer electrolyte membranes (PEMs) for fuel cells, the proton conducting ability is mainly influenced by the distribution and morphology of the water channels inside the PEMs. Non-perfluorinated hydrocarbon PEMs are known to have weaker water channels than perfluorinated PEM, Nafion, and thus relatively low proton conducting ability. In this study, we used a mesoscale simulation technique to observe the water channel formation and phase separation behavior of hydrocarbon PEM, sulfonated polyimides, under the humidification condition. It was observed that the water molecules were distributed evenly through the entire hydrophilic region, and clear water clusters were formed only in the sulfonated polyimide having high sulfonation degree. In addition, it was observed that sulfonated polyimides have a difficulty in forming water channel under the low hydrated condition. These results clearly support the theories of the formation of water channels in non-perfluorinated hydrocarbon PEMs, and also well explain the tendency of proton conducting abilities of sulfonated polyimides. Thus, it is confirmed that mesoscale simulation techniques can be very effective in analyzing phase separation behavior and water channel formation in PEMs for fuel cells and elucidating the ion conducting abilities.

• Korean journal of applied entomology
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• v.23 no.2 s.59
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• pp.82-88
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• 1984

Fruit rot and blister canker, a disease of apple occurring severely in Korea has been studied for correct identification of the syndrome In fruit and apple trees. Among the fungi isolated from blister cankers, rough barks or fruits showing rotting of 7 different host species were Botryosphaeria berengeriana (pycnidial stage. Dethiorella mali), Penicillium expansum and Alternaria sp. from apple rots and Phomopsis sp. from pear fruit rots. The most dominant isolates were B. berengeriana. Ten isolates of D. mali were grouped in to two conidial types based up mycelial growth rate, growth habits and mycelial coloration on PDA. None of 10 isolates was chromogenic. Pycnidia in apple stems, stromatic, dark brown, globose or subglobose and the measuring were $103.5-287.5{\mu}\times92.0-287.5\mu$. The pycnidia contained hyaline, nonseptate, fusiform conidia. The sizes of pycnidiospore of isolates obtained from apple twig were $4.3-7.2{\mu}\times20.0-31.5{\mu}(average\;5.9\times25.4\mu)$. Some conidia of this fungus from apple, pear, peach and ornamental cherry showed 1-,2-,3-septate before or during germination. Microconidia were observed in pycnidia on PDA and fruit lesion of inoculated host. Symptoms on leaves and fruits were contoured brown spots when inoculated. Wart-like protuberance were formed on the surface of apple and pear. Canker appeared on branches of peach and ornamental cherry inoculated.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.3
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• pp.244-252
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• 2005

It is very interesting and important in the academic point of view and in practical use the hydrogen-induced phase separation(HIPS) which appears during hydrogen heat treatment. Since hydrogen can be removed very fast by pumping it out the hydrogen-induced new lattice phase which can not be obtained without hydrogen can be preserved as meta-stable state. In this study it has been investigated whether the HIPS appear in Pd-Al, Pd-Co, Pd-Cr, Pd-Ti, Pd-V and Pd-Zr alloys and discussed thermodynamic representation of the HIPS. The Pd alloys were arc-melted under argon atmosphere and remelted 4 or 5 times for homogenization. The alloys were annealed at 600$^{\circ}C$ under vacuum for 24 hrs and then subjected to pressure-composition isotherm measurements at 100$^{\circ}C$. The hydrogen heat treatment(HHT) of samples was carried out at 600$^{\circ}C$ under hydrogen pressure of 70 bar for 6 days and PC isotherms at 100$^{\circ}C$ were measured. By comparing the PC isotherms measured before and after HHT, occurrence of phase separation was determined. The experimental results showed that the HIPS appeared only in Pd-0.05Co alloy. For Pd-Co alloys with various composition the PC isotherms were measured. By adopting Park-Flanagan model for ternary thermodynamics the Gibbs free energy change for Pd-Co-H solid solution was calculated and subsequently with this the HIPS in Pd-Co alloy was explained fairly.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.515-522
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• 1999

Asymmetric polyetherimide membrane were prepared by phase inversion method, and the effects of NaOH concentration and reaction time on the morphology change of the polyetherimide membranes were studied. The morphology of skin layers varied from dense structure to sphere structure with increasing concentration of modification solution. The thickness of dense layer increased with increasing reaction time. However, when either the concentration of modifying solution was very high or the reaction time was very long, the dense layers of the asymmetric membrane were disappeared. From these results, it was found that the surface morphology of the asymmetric polyetherimide membranes depended strongly on the modification conditions such as concentration of modification solution and reaction time. These results might be explained by the hydrolysis reaction of polyetherimide into polyamic acid by the NaOH solution.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.502-502
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• 2011

기존 연구에서는 단일 타겟으로부터 증착된 코팅층 내에 다상으로 이루어진 나노 복합구조를 형성하기 위하여, 나노 합금분말을 방전플라즈마 소결법 등으로 급속 소결하여 타겟을 제조하는 방법이 고려되어 왔다. 반면, 비정질 재료가 우수한 비정질 형성능을 가지는 경우 주조 방법에 의해서도 타겟 제조가 가능하며, 특히 최근 들어 금속 비정질 합금에서 합금의 주요 구성 원소들이 양의 혼합열을 가지는 경우, 액상 또는 과냉각 액상에서 상분리 현상이 발생한다는 것이 밝혀졌다. 이러한 사실에 기초하면, 우수한 비정질 형성능을 가지는 합금 시스템에 합금 구성 원소와 양의 혼합열 관계를 갖는 원소를 첨가함으로써, 비정질 기지 내에 화학적 불균일성을 유도하여 다상으로 이루어진 복합 구조를 형성시키는 것이 가능하다. 본 연구에서는 이러한 합금 설계법을 이용하여, 비정질 기지 내에 존재할 수 있는 불균일성 정도를 합금 조성과 주조 조건의 변화를 통하여 나노 크기에서 원자 크기까지 조절하고, 이에 따른 재료 특성과의 상관관계를 밝히고자 하였다. 이를 위하여 우수한 비정질 형성능을 가지는 Cu-(Zr, Hf)-Al 벌크 비정질 합금계에서 (Zr, Hf)과 (Y, Gd)간의 양의 혼합열 관계에 주목하여 Cu-(Zr, Hf)-(Y, Gd)-Al 벌크 비정질 형성 합금계를 설계하였으며, 이 합금계 내에서 조성과 냉각속도의 조절에 따라 나타나는 불균일성의 정도와 특성변화의 영향을 체계적으로 고찰하였다. 결과로서, Cu-(Zr, Hf)-Al 합금계에서 (Zr, Hf)을 (Y, Gd)으로 15 at.% 이상 치환한 경우, Cu-(Zr, Hf)-rich 와 Cu-(Y, Gd)-rich 비정질상으로 이상분리가 일어났으며, 이렇게 생성된 비정질-비정질 복합재는 응력 하에서 소성 변형을 거의 보이지 않았다. 반면, 5 at.% 이하로 (Zr, Hf)을 (Y, Gd)으로 치환한 경우에는 비정질 기지에 SAXS 혹은 WAXS로 확인 가능한 원자 크기의 불균일성이 나타났으며, 이 경우 비정질 합금의 점성 유동의 변화를 통해 합금의 연신 특성이 향상되었다. 특히, 본 연구에서는 비정질 기지내 불균일 제어를 통한 기계적 특성 향상을 위해서 조성 제어뿐 아니라 동역학적인 요소를 고려한 냉각속도 조절을 통한 원자단위 불균일성의 최적화가 필요함을 규명하였다. 이러한 연구 결과는 분말화 및 소결 과정을 배제하고 제조된 단일 타겟을 통해 코팅층에 다수의 합금원소를 혼합하고 나노/원자 스케일의 복합구조 형성 및 고집적화가 가능한, 타겟 모물질 설계의 새로운 방향을 제시함으로써 다기능성 복합소재 코팅층의 연구에 크게 기여할 것으로 사료된다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.5
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• pp.225-229
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• 2015

This study was performed to investigate crystal structure of cubic spinel-type monophase oxide composed of the Mn-Co-Ni ternary system. Starting material was prepared by mixing Mn, Co, Ni oxides then evaporation to dryness. The XRD patterns were analyzed by in-situ XRD as increasing temperature from room temperature to $1400^{\circ}C$ in air atmosphere. The cubic spinel phase was existed in a temperature range from $900^{\circ}C$. However, separation of NiO phase was detected from $1300^{\circ}C$, which was the origin of deterioration in the crytallinity. The surface morphology of the manufactured NTC thermistors were analyzed by FE-SEM for comparison of good and bad samples.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1677-1680
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• 2006

하수처리장의 침전지 구조물은 고형물(SS) 및 현탁물을 침전, 제거하여 하수의 정화를 도모하는 시설로 초기 유입 하수의 생물학적 처리로 인해 발생되는 슬러지와 처리수를 분리함에 그 목적을 두고 있다. 침전지 구조물은 장소의 제약 및 침전지의 효율성 측면에서 많은 공법이 제안되고 있으며, 그중 이층 침전지의 경우 구조물의 시공비용 절감 및 공간 활용측면에서 단층 침전지에 비해 우수성을 인정받고 있다. 하지만 상 하 층에 위치하고 있는 침전지 유입부의 위치적 특성으로 인해 균등한 유량의 분배가 이루어지지 않고 유량이 한곳에 집중되는 현상으로 보일 수 있다. 본 연구에서는 3차원 수치모형인 FLOW-3D를 이용하여 이층 침전지의 유량분배 최적화를 위한 설계인자를 도출 하였다. 특히 상 하층에 위치하고 있는 유입부의 위치적인 특성을 고려하여 유입부의 직경을 상층 $500mm{\sim}600mm$, 하층 $500mm{\sim}700mm$으로 변화시키며 수치모의를 수행하였으며, 유입량의 분배효과를 확인하기 위해 각 동일한 위치에서 유입량을 산정하였다. 각 케이스별 분배효과를 분석한 결과 상 하층의 유입부 직경을 상층 600mm 와 하층 700mm를 적용했을 경우 유입량의 표준편차가 가장 작게 발생하며, 침전지 내부의 흐름이 원활하게 이루어지는 것으로 확인되었다. 본 연구에서는 상용 CFD모형인 FLOW-3D를 계획 중인 H하수처리장의 이층 침전지 설계에 적용하였으며 유입부 직경에 따른 분배효과를 분석하였다.