• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.85-91
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• 2009

There has been a rapid progress for flexible polymer-based MEMS(Microelectromechanical Systems) technology. Polycarbonate (PC) and Poly Methyl Methacrylate (PMMA), so-called acrylic, have many advantages for optical, non-toxic and micro-device application. We studied dry etching of PC and PMMA as a function of % gas ratio in the $O_2/SF_6/CH_4$ temary plasma. A photoresist pattern was defined on the polymer samples with a mask using a conventional lithography. Plasma etching was done at 100 W RIE chuck power and 10 sccm total gas flow rate. The etch rates of PMMA were typically 2 times higher than those of PC in the whole experimental range. The result would be related to higher melting point of PC compared to that of PMMA. The highest etch rates of PMMA and PC were found in the $O_2/SF_6$ discharges among $O_2/SF_6$, $O_2/CH_4$ and $SF_6/CH_4$ and $O_2/SF_6/CH_4$ plasma composition (PC: ${\sim}350\;nm/min$ at 5 sccm $O_2/5$ sccm $SF_6$, PMMA: ${\sim}570\;nm/min$ at 2.5 sccm $O_2/7.5$ sccm $SF_6$). PC has smoother surface morphology than PMMA after etching in the $O_2/SF_6/CH_4$ discharges. The surface roughness of PC was in the range of 1.9$\sim$3.88 nm. However, that of PMMA was 17.3$\sim$26.1 nm.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.495-500
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• 2009

Actinide sorption to the geological materials can reduce the mobility and bioavailability of radionuclides released to the environment through the development of nuclear weapons and nuclear energy. Under circumneutral pH conditions, actinide sorption can be enhanced by phosphate anions sorbed on oxide mineral surfaces as indicated by the sorption of trivalent lanthanide ions ($Ln^{3+}$), the chemical analog for trivalent actinide ions ($Ac^{3+}$). In this paper, we examined a ternary sorption system of trivalent europium ions ($Eu^{3+}$) sorbed onto boehmite (${\gamma}$-AlOOH) surfaces pre-sorbed with phosphate anions (${PO_4}^{3-}$), using extended X-ray absorption fine structure (EXAFS) spectroscopy. In the Eu-$PO_4$-boehmite ternary sorption system, $EuPO_4$ surface precipitates were formed as implicated by Eu $L_{III}$-edge EXAFS spectroscopy. Phosphorus K-edge EXAFS fingerprinting indicated a bidentate mononuclear surface complex formation of phosphate sorbed on boehmite surfaces as well as $EuPO_4$ surface precipitate formation.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.3
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• pp.41-47
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• 2009

Post-tensioned concrete pavement(PTCP) was developed to built long-span concrete pavement(120 m span) and to maintain long-term service life(over 40 years) of concrete pavement. In the present study, research for high-durable concrete was conducted to utilize the advantage of PTCP construction method efficiently. First of all, 20% of fly ash(by binder weight) was replaced to control alkali silica reaction. Second, silica fume was applied to improve the water-permeability and early-age strength. Results of tests for mechanical properties, water-permeability resistance, and surface-scaling resistance of ternary blended cement concrete showed that the early-age strength was improved significantly with addition of silica fume. The water-permeability resistance was improved from "Low" to "Very Low"(ASTM C 1202). However, surface-scaling resistance was decreased with an increase of silica fume, therefore, content of silica fume should be kept in less than 5%(by binder weight) to assure field application considering durability. The results of air-void analysis showed that durability factors were improved since spacing factors were estimated as 250$\pm$15 micron in adjusted mixtures.

• Polymer(Korea)
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• v.32 no.1
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• pp.63-69
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• 2008

The mechanical properties and morphologies of cellulose blends with two different additives were compared. Poly (vinyl alcohol) (PVA) of ethylene glycol (EG) were used as additives in the formation of cellulose blends through the solution blending. The properties of blends were varied with the additive content in the polymer matrix. The ultimate tensile strength and initial modulus of the cellulose blends were highest for a blend PVA content of 30 wt% and for a blend EG content of 10 wt%, respectively. Ternary blended systems of composition of cellulose/PVA (70/30=w/w)/EG were also prepared by the solution blending method with different EG contents. The mechanical properties of these systems were found to be optimal for EG contents of up to 40 wt%. The mechanical properties of the cellulose ternary blend films were superior to those of the cellulose binary blend films. The oxygen permeability transmission rate ($O_2TR$) monotonically decreased with increasing EG content in the ternary blend films. Overall, the mechanical properties of the cellulose blend films were found to be better than those of pure cellulose films.

• Journal of the Korean Society of Radiology
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• v.85 no.3
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• pp.505-519
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• 2024

MRI plays a crucial role in bone marrow (BM) assessment, and has very high sensitivity in diagnosing marrow disorders. However, for radiologists who may not frequently encounter pediatric imaging, distinguishing pathologic BM lesion from normal BM can be challenging. Conditions involving the BM in pediatric patients, such as leukemia and metastatic neuroblastoma, often manifest with diverse musculoskeletal symptoms and may be diagnosed using musculoskeletal MRI examinations. Accurate interpretation of pediatric MRI requires not only an understanding of the normal composition of BM but also an awareness of age-related developmental changes in the marrow and familiarity with conditions that commonly involve pediatric BM. We aim to describe the composition of normal BM and outline the normal and abnormal MRI findings in pediatric BM. Additionally, we aim to present clinical cases of malignant BM disorders including leukemia, neuroblastoma metastasis, and other malignant BM disorders.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2008.11a
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• pp.37-51
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• 2008

인삼은 재배적지에 대한 선택성이 매우 강한 식물이며, 기후 토양 등의 자연환경이 적당하지 않으면 인삼의 생육이 곤란하고, 생육이 가능하더라도 생산된 인삼의 형태, 품질 및 약효에서 현저한 차이를 나타내고 있다. 이러한 인삼의 식물학적 특성이 우리나라에서는 최적의 환경조건으로 인정되어 고려인삼은 세계적으로 최고의 품질로 높이 평가되는 이유이다. 하지만 실질적인 인삼의 생리활성물질에 대한 연구는 서구열강 및 일본에 의해 대다수 연구, 발표되었으며 또한 인삼의 우수성을 인정하여 넓은 영토와 수많은 과학적 지식으로 고려인삼의 우수한 품질을 앞서가려 하고 있는 것이 현실정이다. 특히 중국의 넓은 인삼재배면적에서 값싸게 생산된 인삼이 한국시장을 위협하고 있으며, 미국과 캐나다에서 수많은 연구비를 투자하여 자국삼인 화기삼의 홍보를 대대적으로 함으로서 전세계의 인삼시장의 변화를 유도하고 있고, 호주, 뉴질랜드에서도 청정인삼을 내세워 한국 및 전세계 인삼시장을 잠식해가고 있다. 이런 변화에 의하여 한때 인삼의 종주국으로 전세계의 인삼시장을 석권했던 한국의 고려인삼이 과거의 위상을 점차 잃어 가고 있는 실정이다. 따라서 인삼재배면적이 경쟁국과 비교해 상대적으로 열세인 한국의 고려인삼이 선택할수 있는 방법은 비록 생산은 적더라도 고부가가치인삼을 생산하여 명품화로 가야 할 것으로 생각된다. 명품화를 위해서는 우선 고려인삼의 효능을 밝혀 고기능성을 입증해야하고, 재배생산단계에서부터 농약, 중금속등에 노출되지 않고 병에 자유로운 청정재배를 통해 명품화를 이룩해야 하며, 특히 제품의 생산 및 유통단계에서 표준화를 통해서 전세계의 소비자가 믿고 사용할수 있도록 해야 할 것이다. 또한 인삼에만 함유된 인삼사포닌(ginsenoside)은 배당체로서 여러 미생물에 의하여 당사슬이 끊어짐으로서 새로운 사포닌이 등장하게 되는데 이러한 사포닌이 각종 함암, 면적, 치매, 관절등에 탁월한 효능을 보임으서 많은 연구들이 진행중에 있으며, 특히 인삼에만 함유된 것으로 알고 있었던 ginsenoside가 돌외(한약재명 칠엽담)에도 함유되어 있고 일부 성분은 미생물을 통해서 변환시킴으로 서 값비싼 인삼사포닌을 생장이 빠르면 비교적 값싼 돌외 사포닌으로부터 생산할수 있게 되었다. 본 세미나에서는 각종 미생물을 이용하여 인삼의 사포닌을 변환시키고 돌외 사포닌인 gypenoside를 ginsenoside로 변환시켜 대량생산할 수 있는 방법을 제시하고자 한다.

• Journal of the Korean Institute of Gas
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• v.22 no.2
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• pp.52-58
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• 2018

The flash point is one of the most important properties to characterize fire and explosion hazard of flammable liquid mixture. In this paper, the flash points of ternary liquid mixture, n-nonane+n-decane+n-tridecane system, were measured using Seta flash closed cup tester. The measured values were compared with the calculated values using Raoult's law and multiple regression analysis. The absolute average errors(AAE) of the results calculated by Raoult's law is $0.6^{\circ}C$. The absolute average errors of the results calculated by multiple regression analysis is $0.4^{\circ}C$. As can be seen from AAE, the calculated values based on multiple regresstion analysis were found to be better than those based on Raoult's law.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.269-274
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• 2010

The solubility and the physicochemical property (refractive index) in the NaCl-$CaCl_2$-$H_2O$ and KCl-$CaCl_2$-$H_2O$ systems were determined at $50^{\circ}C$ and the phase diagrams and the diagrams of physicochemical property vs composition were plotted. One invariant point, two univariant curves, and two crystallization zones, corresponding to sodium Chloride (or potassium chloride), dihydrate ($CaCl_2{\cdot}2H_2O$) showed up in the phase diagrams of the ternary systems. The mixing parameters ${\theta}_{M,Ca}$ and ${\Psi}_{M,Ca,Cl}$ (M = Na or K) and equilibrium constant $K_{sp}$ were evaluated in NaCl-$CaCl_2-H_2O$ and KCl-$CaCl_2-H_2O$ systems by least-squares optimization procedure, in which the single-salt Pitzer parameters of NaCl, KCl and $CaCl_2$ ${\beta}^{(0)}$, ${\beta}^{(1)}$, ${\beta}^{(2)}$ and $C^{\Phi}$ were directly calculated from the literature. The results obtained were in good agreement with the experimental data.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.3
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• pp.269-276
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• 2005

Zn, Bi 와 V 금속이온 전구체를 사용하여 모노클리닉 결정구조를 갖는 신규 ZnBiVO4 광촉매를 손쉽게 합성 할 수 있는 방법을 개발하였다. 합성된 $ZnBiVO_4$ 광촉매는 XRD 과 FESEM등을 이용하여 미세구조를 분석하였으며, 분석결과 본 삼성분계 금속산화물 반도체 광촉매는 모노클리닉 결정구조를 갖는 것을 알 수 있었다. 저온 수용액방법에 의해 손쉽게 나노 구조를 갖는 $ZnBiVO_4$가 제조되었으며, 그 광촉매의 최소 입자크기는 20-30 nm 이다. $ZnBiVO_4$ 광촉매는 UV-visible DRS (diffuse reflectance spectroscopy)로 그 띠간격(band gap)을 측정하였으며, FT-IR을 사용하여 구조 및 물질 상의 순도를 확인하였다. 그리고 $H_2S$를 광분해하여 수소를 발생하는($122ml/hr{\cdot}g$) 우수한 광촉매 활성을 보여 주었다.

• Polymer(Korea)
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• v.38 no.4
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• pp.449-456
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• 2014

Ternary blends of poly(L-lactic acid) (PLLA), poly(${\varepsilon}$-caprolactone) (PCL) and polyethylene oxide (PEO) were produced with different concentrations of components via melt blending. By leaching the PEO from the samples by water, porous materials were obtained with potential application for bio scaffolds. Sample porosity was evaluated by calculating the ratio of porous scaffold density (${\rho}^*$) to the non-porous material density (${\rho}_s$). Highest porosity (51.42%) was related to the samples containing 50 wt%. of PEO. Scanning electron microscopy (SEM) studies showed the best porosity resulted by decreasing PLLA/PCL ratio at constant concentration of PEO. Crystallization behavior of the ternary blend samples was studied using differential scanning calorimetry (DSC). Results revealed that the crystallinity of PLLA was improved by addition of PEO and PCL to the samples. The porosity plays a key role in governing the compression properties. Mechanical properties are presented by Gibson-Ashby model.